[Federal Register Volume 81, Number 150 (Thursday, August 4, 2016)]
[Notices]
[Pages 51694-51724]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2016-18462]
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Vol. 81
Thursday,
No. 150
August 4, 2016
Part IV
Department of Commerce
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National Oceanic and Atmospheric Administration
Technical Guidance for Assessing the Effects of Anthropogenic Sound on
Marine Mammal Hearing--Underwater Acoustic Thresholds for Onset of
Permanent and Temporary Threshold Shifts; Notice
Federal Register / Vol. 81 , No. 150 / Thursday, August 4, 2016 /
Notices
[[Page 51694]]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XC969
Technical Guidance for Assessing the Effects of Anthropogenic
Sound on Marine Mammal Hearing--Underwater Acoustic Thresholds for
Onset of Permanent and Temporary Threshold Shifts
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice.
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SUMMARY: The National Marine Fisheries Service (NMFS) announces the
availability of its final Technical Guidance for Assessing the Effects
of Anthropogenic Sound on Marine Mammal Hearing--Underwater Acoustic
Thresholds for Onset of Permanent and Temporary Threshold Shifts
(Technical Guidance or Guidance) that provides updated received levels,
or acoustic thresholds, above which individual marine mammals under
NMFS' jurisdiction are predicted to experience changes in their hearing
sensitivity (either temporary or permanent) for all underwater
anthropogenic sound sources.
ADDRESSES: The Technical Guidance is available in electronic form via
the Internet at http://www.nmfs.noaa.gov/pr/acoustics/.
FOR FURTHER INFORMATION CONTACT: Amy R. Scholik-Schlomer, Office of
Protected Resources, 301-427-8449, [email protected].
SUPPLEMENTARY INFORMATION: The National Marine Fisheries Service in
consultation with the National Ocean Service has developed Technical
Guidance to help assess the effects of underwater anthropogenic sound
on marine mammal species under NMFS' jurisdiction. Specifically, the
Guidance identifies the received levels, or acoustic thresholds, above
which individual marine mammals are predicted to experience changes in
their hearing sensitivity (either temporary or permanent) for all
underwater anthropogenic sound sources. NMFS compiled, interpreted, and
synthesized scientific literature to produce updated acoustic
thresholds for the onset of both temporary (TTS) and permanent
threshold shifts (PTS). This is the first time NMFS has presented this
information in a single, comprehensive document. This Technical
Guidance is intended for use by NMFS analysts and managers and other
relevant user groups and stakeholders, including other federal
agencies, when seeking to determine whether and how their activities
are expected to result in hearing impacts to marine mammals via
acoustic exposure.
The main body of the document contains NMFS' updated acoustic
thresholds for onset of PTS for marine mammals exposed to underwater
sound and NMFS' plan for periodically updating acoustic thresholds.
Other information such as details on the development marine mammal
auditory weighting functions and acoustic thresholds, research
recommendations, alternative methodology (formerly referred to as a
User Guide), the peer review and public comment process, and a glossary
of acoustic terms can be found in the Technical Guidance appendices.
These thresholds update those currently in use by NMFS. Updates
include a protocol for deriving PTS and TTS onset levels for impulsive
(e.g., airguns, impact pile drivers) and non-impulsive (e.g., tactical
sonar, vibratory pile drivers) sound sources and the formation of
marine mammal hearing groups (low- (LF), mid- (MF), and high-frequency
(HF) cetaceans and otariid (OW) and phocid (PW) pinnipeds in water) and
associated auditory weighting functions. Acoustic thresholds are
presented using the dual metrics of cumulative sound exposure level
(SELcum) and peak sound pressure level (PK) for impulsive
sounds and the SELcum metric for non-impulsive sounds. While
the updated acoustic thresholds are more complex than what has been in
use by NMFS and regulated entities, they more accurately reflect the
current state of scientific knowledge regarding the characteristics of
sound that have the potential to impact marine mammal hearing
sensitivity. Given the specific nature of these updates, it is not
possible to generally or directly compare the updated acoustic
thresholds presented in this document with the thresholds they will
replace because outcomes will depend on project-specific
specifications.
Although NMFS has updated the acoustic thresholds, and these
changes may necessitate new methodologies for calculating impacts, the
application of the thresholds in the regulatory context of applicable
statutes (Marine Mammal Protection Act (MMPA), Endangered Species Act
(ESA), and National Marine Sanctuaries Act (NMSA)) remains consistent
with current NOAA practice (see Regulatory Context in this Federal
Register Notice). It is important to emphasize that these updated
acoustic thresholds do not represent the entirety of an impact
assessment, but rather serve as one tool (in addition to behavioral
impact thresholds, auditory masking assessments, evaluations to help
understand the ultimate effects of any particular type of impact on an
individual's fitness, population assessments, etc.), to help evaluate
the effects of a proposed action.
NMFS recognizes that action proponents may have varying abilities
to model and estimate exposure and that the Technical Guidance may be
more complex than some action proponents are able to incorporate. Thus,
NMFS has provided alternative methodology and an associated User
Spreadsheet to aid action proponents with SELcum thresholds
and marine mammal auditory weighting functions (http://www.nmfs.noaa.gov/pr/acoustics/).
The Technical Guidance is classified as a Highly Influential
Scientific Assessment (HISA) by the Office of Management and Budget. As
such, three independent peer reviews were undertaken, at three
different stages of the development of the Technical Guidance,
including a follow-up to one of the peer reviews, prior to broad public
dissemination by the Federal Government. Details of each peer review
can be found within the Technical Guidance (Appendix C) and at the
following Web site: http://www.nmfs.noaa.gov/pr/acoustics/. NMFS
acknowledges and thanks the Marine Mammal Commission (Commission) and
the Acoustical Society of America's Underwater Technical Council for
nominating peer reviewers and thanks the peer reviewers for their time
and expertise in reviewing this document.
In additional to three independent peer reviews, the Technical
Guidance was the subject of three public comment periods. NMFS
evaluated all substantive comments made during each public comment
period to determine their relevance to the Technical Guidance as it was
revised. Public comments made on aspects of the Technical Guidance that
are no longer relevant have not been included here. Substantive and
relevant comments and NMFS' responses are included below (see Comments
and Responses).
The Technical Guidance does not create or confer any rights for or
on any person, or operate to bind the public. An alternative approach
that has undergone independent peer review may be proposed (by federal
agencies or prospective action proponents) and used if case-specific
information/data indicate that the alternative approach is likely to
produce a more accurate
[[Page 51695]]
portrayal of take for the project being evaluated, if NOAA determines
the approach satisfies the requirements of the applicable statutes and
regulations.
Transitioning to the Technical Guidance
NMFS considers the updated thresholds and associated weighting
functions in the Technical Guidance to be the best available
information for assessing whether exposure to specific activities is
likely to result in changes in marine mammal hearing sensitivity
(temporary or permanent). Prospective applicants for incidental take
authorizations under the MMPA and federal agencies seeking ESA section
7 consultations that have not yet started their acoustic analyses
should begin using the new Technical Guidance immediately. At the same
time, we recognize that for some proposed actions, analyses may have
already substantially progressed using the existing thresholds or other
methods for assessing hearing effects, and it may be impractical to
begin those analyses anew, taking into account timing constraints,
expense, and other considerations. In such ``pipeline'' cases, the
applicant or action agency should contact NMFS as soon as possible to
discuss how to best include consideration of the Technical Guidance to
satisfy the applicable requirements. A non-exhaustive list of factors
that could affect the extent to which the Technical Guidance will be
considered for an action include: The relative degree to which the
Technical Guidance is expected to affect the results of the acoustic
impact analyses; how far in the process the application or prospective
application has progressed; when the activity is scheduled to begin or
other timing constraints; the complexity of the analyses and the cost
and practicality of redoing them; and the temporal and spatial scope of
anticipated effects. We anticipate that after the initial transition
period, all applications for MMPA incidental take authorization (ITA)
and all requests for ESA section 7 consultations involving noise that
may affect marine mammals will include full consideration of the
Technical Guidance.
National Environmental Policy Act (NEPA)
In 2005, NMFS published a Federal Register Notice of Public Scoping
and Intent to Prepare an EIS for a similar action (70 FR 1871, January
11, 2005). The nature of the Guidance has evolved significantly since
then. After evaluating the contents of the Technical Guidance and the
standards for a categorical exclusion under NAO 216-6, sec. 6.03c.3(i),
we have determined the Technical Guidance is categorically excluded
from further NEPA review.
NAO 216-6, sec. 6.03c.3(i), provides that a categorical exclusion
is appropriate for ``policy directives, regulations, and guidelines of
an administrative, technical, or procedural nature, or the
environmental effects of which are too broad, speculative or
conjectural to lend themselves to meaningful analysis and will be
subject later to the NEPA process, either collectively or case by
case.''
Although changes to the PTS and TTS thresholds will likely change
the take estimates for at least some portion of activities, any
environmental effects of the draft guidance alone, without reference to
a specific activity, are too speculative or conjectural to lend
themselves to meaningful analysis at this stage. Effects analyses under
the MMPA, ESA, and NMSA (and appropriate mitigation and monitoring) are
activity-specific exercises that cannot be conducted absent some level
of specificity regarding the nature of the proposed activity, the
general location, and the time and duration. Moreover, direct
comparisons cannot be made between the thresholds currently used and
the updated thresholds, due to the different metrics and taxa-specific
frequency weighting used in the new thresholds.
Any environmental effects from application of the updated PTS and
TTS thresholds will flow from future actions that are the subject of
ITAs under the MMPA and related consultations under the ESA or NMSA.
The nature and magnitude of such effects will depend on the specific
actions themselves, each of which would be subject to the NEPA process.
Because any effects from the Technical Guidance are speculative and
conjectural, NOAA has determined it cannot meaningfully analyze
potential effects in the manner contemplated by NEPA, which is to
inform agency decisions about the effects of an action (and reasonable
alternatives) on the environment. Any changes in future effects
analyses resulting from the Guidance will be part of the NEPA and other
statutorily-required analyses conducted for specific actions in the
future.
Finally, the proposed action does not trigger any of the exceptions
for categorical exclusions described in section 5.05c of NAO 216-6. It
does not involve a geographic area with unique characteristics, is not
a subject of public controversy due to potential environmental
consequences, have uncertain environmental impacts or unique or unknown
risks, establish a precedent or decision in principle about future
proposals, result in cumulatively significant impacts, or have any
adverse effects upon endangered or threatened species or their
habitats.
Regulatory Context
NMFS uses acoustic thresholds to help quantify ``take'' and as part
of more comprehensive effects analyses under several statutes. The
Technical Guidance's updated acoustic thresholds do not represent the
entirety of the comprehensive effects analysis, but rather serve as one
tool among others (e.g., behavioral impact thresholds, auditory masking
assessments, evaluations to help understand the ultimate effects of any
particular type of impact on an individual's fitness, population
assessments, etc.) to help evaluate the effects of a proposed action
and make findings required by NOAA's various statutes.
Under current agency practice, NMFS considers the onset of PTS,
which is an auditory injury, as an example of ``Level A Harassment'' as
defined in the MMPA and as ``harm'' as defined in ESA regulations, such
that exposing an animal to weighted received sound levels at or above
the indicated PTS threshold is predicted to result in these two types
of ``take'' (i.e., Level A Harassment under the MMPA and harm under
ESA).
As explained below, NMFS does not consider a TTS to be an auditory
injury under the MMPA or ESA, and thus it does not qualify as Level A
harassment or harm. Nevertheless, TTS is an adverse effect that
historically has been treated as ``take'' by ``Level B Harassment''
under the MMPA and ``harassment'' under the ESA. The broad definition
of ``injury'' under the NMSA regulations includes both PTS and TTS (as
well as other adverse changes in physical or behavioral characteristics
that are not addressed in the Technical Guidance).
Marine Mammal Protection Act
The MMPA prohibits the take of marine mammals, with certain
exceptions, one of which is the issuance of ITAs. Sections 101(a)(5)(A)
& (D) of the MMPA (16 U.S.C. 1361 et seq.) direct the Secretary of
Commerce to allow, upon request, the incidental, but not intentional,
taking of small numbers of marine mammals by U.S. citizens who engage
in a specified activity (other than commercial fishing) within a
specified geographical region if certain findings are made. Through
delegation by the Secretary of Commerce, NMFS is
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required to authorize the incidental taking of marine mammals if it
finds that the total taking will have a negligible impact on the
species or stock(s) and will not have an unmitigable adverse impact on
the availability of the species or stock(s) for certain subsistence
uses. NMFS must also set forth the permissible methods of taking and
requirements pertaining to the mitigation, monitoring, and reporting of
such takings. (The ``small numbers'' and ``specified geographical
region'' provisions do not apply to military readiness activities.)
The term ``take'' means to harass, hunt, capture, or kill, or
attempt to harass, hunt, capture or kill any marine mammal. 16 U.S.C.
1362(13).
Except with respect to certain activities described below,
``harassment'' means any act of pursuit, torment, or annoyance which:
Has the potential to injure a marine mammal or marine
mammal stock in the wild (Level A Harassment), or
Has the potential to disturb a marine mammal or marine
mammal stock in the wild by causing disruption of behavioral
patterns, including, but not limited to, migration, breathing,
nursing, breeding, feeding or sheltering (Level B Harassment).
See id. at 1362(18)(A)(i) & (ii) (emphasis added).
Congress amended the definition of ``harassment'' as it applies to
a ``military readiness activity'' or research conducted by or on behalf
of the federal government consistent with MMPA section 104(c)(3) as
follows (section 3(18)(B) of the MMPA):
Any act that injures or has the significant potential
to injure a marine mammal or marine mammal stock in the wild (Level
A Harassment); or
Any act that disturbs or is likely to disturb a marine
mammal or marine mammal stock in the wild by causing disruption of
natural behavioral patterns, including, but not limited to,
migration, surfacing, nursing, breeding, feeding, or sheltering, to
a point where such behavioral patterns are abandoned or
significantly altered (Level B Harassment).
See id. at 1362(18)(B)(i) & (ii) (emphasis added).
The term ``negligible impact'' is defined as an impact resulting
from the specified activity that cannot be reasonably expected to, and
is not reasonably likely to, adversely affect the species or stock
through effects on annual rates of recruitment or survival. 50 CFR
216.103.
In support of the analysis that is necessary to make the required
statutory determinations, MMPA implementing regulations require ITA
action proponents to provide NMFS with specific information. Although
they may also be used to inform the development of mitigation measures,
the updated acoustic thresholds are particularly relevant to the
following two of the fourteen required pieces of information:
The type of incidental taking authorization that is
being requested (i.e., takes by Level B Harassment only; Level A
Harassment; or serious injury/mortality) and the method of
incidental taking;
By age, sex, and reproductive condition (if possible),
the number of marine mammals (by species) that may be taken by each
type of taking identified in paragraph (a)(5) of this section, and
the number of times such takings by each type of taking are likely
to occur.
50 CFR 216.104 (emphasis added).
Endangered Species Act
Section 9 of the ESA prohibits the take of ESA-listed species, with
limited exceptions. Section 7 of the ESA requires that each federal
agency, in consultation with NMFS and/or the U.S. Fish and Wildlife
Service (USFWS), ensure that any action authorized, funded, or carried
out by the agency is not likely to jeopardize the continued existence
of any endangered or threatened species or result in the destruction or
adverse modification of designated critical habitat. See 16 U.S.C.
1536(a)(2). Provided that NMFS or the USFWS reaches these conclusions
through a ``formal consultation'' process, incidental take of ESA-
listed species may be exempted from the section 9 take prohibition
through an ``incidental take statement'' that must specify the impact,
i.e., the amount or extent, of the taking on the species. See id. at
section 1536(b)(4). Incidental take statements must also include
reasonable and prudent measures necessary or appropriate to minimize
the impact, and the terms and conditions required to implement those
measures.
Under ESA, ``take'' means to harass, harm, pursue, hunt, shoot,
wound, kill, trap, capture, or collect, or to attempt to engage in any
such conduct. See id.at section 1532(19). ``Harm'' is defined in NMFS
regulations as ``an act which actually kills or injures fish or
wildlife'' (and can include significant habitat modification or
degradation). See 50 CFR 222.102.
Under NMFS and the USFWS implementing regulations for section 7 of
the ESA, ``jeopardize the continued existence of'' means to engage in
an action that reasonably would be expected, directly or indirectly, to
reduce appreciably the likelihood of both the survival and recovery of
a listed species in the wild by reducing the reproduction, numbers, or
distribution of that species. See id.at Sec. 402.02.
In support of the analysis necessary to conduct the consultation,
the ESA implementing regulations state that in order to initiate formal
consultation, the federal action agency must submit a written request
for formal consultation to the Director (of NMFS or the USFWS) that
includes, among other things, a description of the manner in which the
action may affect any listed species. See id.at Sec. 402.14(c).
National Marine Sanctuaries Act
Section 304(d) of the NMSA requires federal agencies whose actions
are likely to destroy, cause the loss of, or injure a sanctuary
resource to consult with the Office of National Marine Sanctuaries
(ONMS) before taking the action. See 16 U.S.C. 1434(d)(1). The NMSA
defines sanctuary resource as ``any living or nonliving resource of a
national marine sanctuary that contributes to the conservation,
recreational, ecological, historical, educational, cultural,
archeological, scientific, or aesthetic value of the sanctuary.''16
U.S.C. 1432(8). Through the sanctuary consultation process, ONMS may
recommend reasonable and prudent alternatives that will protect
sanctuary resources. Recommended alternatives may include alternative
locations, timing, and/or methods for conducting the proposed action.
See id.at Sec. 1434(d)(2). Monitoring may also be recommended to
better characterize impacts to sanctuary resources or accompany
mitigation.
The term ``injure'' is defined in the ONMS implementing regulations
as to ``change adversely, either in the short or long term, a chemical,
biological or physical attribute of, or the viability of.'' 15 CFR
922.3.
In support of the analysis necessary to conduct the consultation,
the NMSA requires that any federal agency proposing an action that may
injure a sanctuary resource provide ONMS with a written statement
(``sanctuary resource statement'') describing the action and its
potential effects on sanctuary resources. See 16 U.S.C. 1434(d)(1)(B).
Application of Acoustic Thresholds for Permanent Threshold Shift
The acoustic thresholds for PTS will be used in conjunction with
sound source characteristics, environmental factors that influence
sound propagation, anticipated marine mammal occurrence and behavior in
the vicinity of the activity, as well as other available activity-
specific factors, to quantitatively estimate (acknowledging the gaps in
scientific knowledge and the
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inherent uncertainties in a marine environment) the takes of marine
mammals (by Level A harassment and harm under the MMPA and ESA,
respectively) and facilitate compliance with the MMPA, ESA, and NMSA as
described above.
NMFS will use the same PTS acoustic thresholds in the
identification and quantification of MMPA Level A harassment for both
military readiness and non-military readiness activities. Because the
acoustic thresholds for PTS predict the onset of PTS, they are
inclusive of the ``potential'' and ``significant potential'' language
in the two definitions of Level A harassment. The limited data now
available do not support the parsing out of a meaningful quantitative
difference between the ``potential'' and ``significant potential'' for
injury and, therefore, the designated PTS acoustic thresholds will be
treated as Level A harassment for both types of activities.
Estimating the numbers of take by Level A harassment and harm is
one component of the fuller analyses that inform NMFS' ``negligible
impact'' and ``jeopardy'' determinations under the MMPA and ESA,
respectively, as well as ``likely to injure'' or ``may affect''
determinations under the NMSA. Last, the PTS acoustic thresholds may be
used to inform the development of mitigation and monitoring measures
(such as shut-down zones) pursuant to the MMPA, ESA, or NMSA.
When initiating any of the MMPA, ESA, or NMSA processes described
above, agencies and other action proponents should utilize the PTS
acoustic thresholds, in combination with activity-specific information,
to predict whether, and if so how many, instances of PTS are expected
to occur.
Application of Acoustic Thresholds for Temporary Threshold Shift
As previously stated, NMFS has not considered TTS an auditory
injury for purposes of the MMPA and ESA, based on the work of a number
of investigators that have measured TTS before and after exposure to
intense sound. For example, Ward (1997) suggested that a TTS is within
the normal bounds of physiological variability and tolerance and does
not represent physical injury. In addition, Southall et al. (2007)
indicates that although PTS is a tissue injury, TTS is not because the
reduced hearing sensitivity following exposure to intense sound results
primarily from fatigue, not loss, of cochlear hair cells and supporting
structures, and is reversible. Accordingly, TTS has been considered
take by Level B harassment under the MMPA and harassment under the ESA,
which will be the subject of future guidance. However, TTS is
considered injury under the broad definition of the term ``injury'' in
NMSA regulations (along with PTS and behavioral impacts). For now, NMFS
will continue the practice of requiring applicants to estimate take by
TTS for explosive sources.
MMPA Level B harassment and ESA harassment are broad categories
that encompass not only TTS but also other behaviorally related impacts
that almost always involve a lower onset threshold than that for onset
of TTS. In quantifying take by Level B harassment or harassment, NMFS
considers all effects that fall into those categories of take, not just
TTS. NMFS will be developing updated acoustic thresholds for the onset
of behavioral effects and will further consider the best approach for
considering TTS at that time. When that process is completed, NMFS will
provide further guidance regarding how to best consider and/or quantify
TTS for non-pulse and impulse sources not involving instantaneous
explosives (see exception below for underwater explosives). In the
meantime, action proponents not using instantaneous explosives do not
need to quantify estimates of TTS separately from their overall
behavioral harassment take calculations. For now, the TTS acoustic
thresholds presented in the Technical Guidance will be considered as
part of the larger comprehensive effects analyses under the MMPA and
the ESA.
With respect to instantaneous explosives (as distinguished from
repeated explosives such as gunnery exercises), NMFS already requires
quantification of TTS estimates because an instantaneous explosive will
not have a separate behavioral component from a lower exposure
threshold and there is no time accumulation involved. The rationale for
calculating TTS for instantaneous explosives continues to apply with
the updated TTS thresholds for explosives.
NMFS is aware of studies by Kujawa and Liberman (2009) and Lin et
al. (2011), which found that despite completely reversible TS that
leave cochlear sensory cells intact, large (but temporary) TS could
cause synaptic level changes and delayed cochlear nerve degeneration in
mice and guinea pigs. However, the large TS (i.e., maximum 40 decibel
dB) that led to the synaptic changes shown in these studies are in the
range of the large shifts used by Southall et al. (2007) and in the
Technical Guidance to define PTS onset (i.e., 40 dB). It is unknown
whether smaller levels of TTS would lead to similar changes or the
long-term implications of irreversible neural degeneration. The effects
of sound exposure on the nervous system are complex, and this will be
re-examined as more data become available.
The occurrence of, and estimated number of, TTS takes is one
component of the larger analysis that informs NMFS's ``negligible
impact'' and ``jeopardy'' determinations under the MMPA and ESA,
respectively, as well as ``likely to injure'' or ``may affect''
determinations under the NMSA. As with PTS, TTS acoustic thresholds
also may be used to inform the development of mitigation and monitoring
measures pursuant to the MMPA, ESA, or NMSA.
Comments and Responses
On December 27, 2013, NMFS published the initial Draft Guidance for
Assessing the Effects of Anthropogenic Sound on Marine Mammals:
Acoustic Thresholds for Onset of Permanent and Temporary Threshold
Shifts for a 30-day public comment period (78 FR 78822), which was
extended an additional 45-days (79 FR 4672; January 29, 2014) based on
public request. During the public comment period, NMFS received
comments from U.S. Representatives from Congress, Federal agencies, an
international government agency, state governments, Alaskan native
groups, industry groups, and non-governmental organizations, individual
subject matter experts, a professional society, a regulatory watchdog
group, and 89 private citizens.
After the close of the initial public comment period, as NMFS was
addressing public comments and working towards finalizing the Guidance,
a new methodology for identifying marine mammal auditory weighting
functions and acoustic thresholds was developed by the U.S. Navy (Dr.
James Finneran, SPAWAR Systems Center Pacific) based on new science.
Additionally, NMFS re-evaluated its methods for defining threshold
usage for sources characterized as impulsive or non-impulsive based on
comments received during the initial public comment period.
Incorporating these updated methodologies resulted in substantial
changes to the Guidance, necessitating additional peer review, as well
as another public comment period. As a result, NMFS solicited public
comment on a revised Draft Guidance (July 2015) via a second 45-day
public comment period (80 FR 45642, July 31, 2015). During the second
public comment period, NMFS received 20 comments from Federal agencies,
industry groups, environmental consultants, Alaskan native groups, non-
governmental
[[Page 51698]]
organizations, individual subject matter experts, a professional
society, a regulatory watchdog group, and two private citizens.
While NMFS was working to address public comments from the second
public comment period and finalize the Guidance, NMFS and the Navy (Dr.
James Finneran, SPAWAR Systems Center Pacific) further evaluated
certain aspects of the U.S. Navy's methodology. As a result of the
Navy's and NMFS' review, several focused recommendations/modifications
were suggested, which did not change the overall methodology provided
in the July 2015 Draft Guidance (the primary changes were related to
deriving a composite audiogram for LF cetaceans). After consideration
of these recommendations, NMFS updated sections of the July 2015 Draft
Guidance to reflect the suggested changes and solicited public comment
on those focused revisions via a focused 14-day public comment period
(81 FR 14095, March 16, 2016). During this third public comment period,
NMFS received 20 comments from Federal agencies, industry groups, non-
governmental organizations, individual subject matter experts, a
professional society, and a private citizen. Please refer to these
Federal Register Notices for additional background about the 2013 and
2015 Draft Guidance, as well as the document containing proposed
changes to the Draft Guidance during the public comment period in 2016.
During these three public comment periods several commenters'
remarks pertained to topics beyond the scope of the final Technical
Guidance (e.g., impacts beyond hearing: Non-auditory injury, mortality,
gas emboli, stranding events, masking, stress, cumulative effects,
ecosystem-wide effects, behavioral disturbance; activity-specific
issues associated with specific permit/authorization; effects of
airborne noise on pinniped hearing; effects of noise on fishes and sea
turtles; propagation modeling; animal distribution/density; data or
modeling requirements; take estimation methodology). NMFS did not
address comments outside the scope of this document. Additionally, in
re-evaluating substantive public comments made during the first (2013/
2014), second (2015), and third (2016) public comment periods, those
earlier comments pertaining to sections of the document no longer
included in the final Technical Guidance are not addressed (e.g.,
proposed 1-hour accumulation period, transition range methodology,
alternative thresholds).
Technical Guidance Scope
Comment 1: Several commenters were concerned about the potential
impacts of sound on polar bear, sea otter, and walrus and asked if NMFS
coordinated with the USFWS or other branches of NMFS when evaluating
and establishing thresholds in the Guidance.
Response: The Technical Guidance only addresses the effects of
underwater anthropogenic sound on marine mammal species under NMFS'
jurisdiction. The Technical Guidance does not pertain to marine mammal
species under the USFWS's jurisdiction (e.g., walrus, polar bears,
manatees, sea otters). The USFWS is aware of this document and was
provided an opportunity to comment. NMFS Headquarters, Regions, and
Science Centers coordinated in the development this Guidance, as did
the National Ocean Service.
Comment 2: Multiple commenters, citing the technical complexity of
the Draft Guidance, requested an extension during all three public
comment periods. Additionally, multiple commenters expressed concern
that the public comment period associated with the March 2016 Proposed
Changes document was rushed, resulted in arbitrary decisions, and did
not allow for meaningful input from those action proponents most
impacted by changes (i.e., activities producing low-frequency sound).
These commenters advocated that instead of NMFS adopting the changes in
the March 2016 document, the July 2015 Draft Guidance instead be
finalized.
Response: NMFS extended the initial 30-day public comment period on
the 2013 Draft Guidance by an additional 45 days (79 FR 4672, January
29, 2014). In consideration of an appropriate duration for the 2015
Draft Guidance public comment period (80 FR 45642, July 31, 2015), NMFS
chose a 45-day (opposed to 30 days) public comment period, based on the
extent of changes from the Draft 2013 Guidance, but did not extend that
public comment period. Regarding the third public comment period, due
to the focused nature of the most recent proposed revision, presented
in a standalone 24-page document, and significant previous
opportunities for public comment, NMFS deemed a 14-day public comment
period appropriate (81 FR, 14095, March 16, 2016) and did not extend
public comment period in response to requests. Based on input received
during the robust review process (i.e., three public comment periods
and three peer reviews, as well as follow-up peer review), NMFS does
not believe additional or extended public comment periods were
necessary to finalize the Technical Guidance.
NMFS disagrees that the March 2016 public comment period was rushed
or resulted in arbitrary decisions. The March 2016 public comment
period was the third opportunity given to the public to review our
Draft Guidance (following the 75-day first public comment period and
45-day second public comment period). Previous versions of the Draft
Guidance had already been revised based upon peer review and public
input. Due to the focused nature of the proposed changes since the
prior draft (which were described in a 24-page standalone document) and
balanced against the lengthy process to date and need for updated
thresholds, NMFS determined a 14-day public comment period was
appropriate.
Comment 3: A few commenters indicated that the 2015 Draft Guidance
and the 2016 Proposed Changes document was incomplete and the Guidance
should not be finalized until the public has an opportunity to comment
on the following missing sections: Agency response to comments made
during the initial and second public comment periods; optional User
Spreadsheet for determining isopleths; and references associated with
sirenian data used in the March 2016 Proposed Changes document.
Response: NMFS disagrees that the 2015 Draft Guidance and 2016
Proposed Changes document were incomplete for public comment. In
finalizing the Technical Guidance (via this Federal Register Notice),
NMFS has addressed to substantive comments provided during all three
public comment periods, except those no longer relevant due to
subsequent changes to the Draft Guidance. Both the 2015 Draft Guidance
and the 2016 Proposed Changes document encompassed modifications based
on comments received during the first and second public comment
periods.
NMFS disagrees that the User Spreadsheet associated with the
Technical Guidance's alternative methodology requires public comment.
This spreadsheet precisely follows the alternative methodology provided
in the Technical Guidance (Appendix D), which was available for public
comment. There is nothing additional or new provided by this
spreadsheet.
As for the sirenian data used in the March 2016 Proposed Changes
document, in response to this comment, these references (Gerstein et
al., 1999; Mann et al., 2009) have been included in the finalized
Technical Guidance. However, NMFS does not believe additional public
review is necessary.
[[Page 51699]]
Comment 4: A few commenters requested clarification as to how the
Technical Guidance will be used in management decisions (i.e., is the
Technical Guidance's use a requirement? Is the Technical Guidance a
rule?).
Response: The Technical Guidance provides a robust assessment and
synthesis of a body of scientifically complex information to assess
impacts of sound on marine mammal hearing. Although its use is not a
binding requirement, it currently reflects the agency's expert
assessment of the scientific literature and represents what the agency
believes is the best approach for assessing auditory impacts. The
Guidance allows for an alternative approach if case-specific
information/data indicate that such an approach is likely, in NMFS'
view following peer review, to produce an equally or a more accurate
estimate of auditory impacts.
Comment 5: Multiple commenters requested NMFS include a brief
statement in the Guidance about what standards are currently in use and
why they need to be updated. Additionally, the Commission requested
that the Guidance include updated explosive thresholds for mortality
(extensive lung injury) and injury (slight lung and gastrointestinal
(G.I.) tract).
Response: A new section has been added to the Technical Guidance
(see Section 1.1 of Main Document) to explain the justification for the
updated acoustic thresholds for PTS and TTS. The Technical Guidance
explicitly indicates that the thresholds within the document are meant
to update all thresholds currently in use by NMFS for assessing PTS
onset, including generic injury thresholds (i.e., root mean square
sound pressure level (RMS SPL) thresholds of 180/190 dB), and PTS/TTS
thresholds for explosives.
NMFS acknowledges that future Technical Guidance is needed for non-
auditory impacts, but is planning on addressing this in a separate
guidance document and recommends current non-auditory thresholds for
explosives remain in use until updates can be completed via the
appropriate processes.
Comment 6: Multiple commenters requested clarification on the
applicability the National Environmental Policy Act (NEPA) to the
Guidance.
Response: NMFS determined that the Technical Guidance satisfies the
standards for a categorical exclusion under NAO 216-6. NAO 216-6, sec.
6.03c.3(i), which provides that a categorical exclusion is appropriate
for ``policy directives, regulations, and guidelines of an
administrative, technical, or procedural nature, or the environmental
effects of which are too broad, speculative or conjectural to lend
themselves to meaningful analysis and will be subject later to the NEPA
process, either collectively or case by case.'' See the section
addressing NEPA earlier in this Notice.
Comment 7: The Center for Regulatory Effectiveness (CRE) indicated
that any use of the Guidance by NMFS in rules would have to be
supported by cost-benefit analyses because it ``could have a potential
impact of more than $500 million in any one year on either the public
or private sector; or . . . the dissemination is novel, controversial,
or precedent-setting; or . . . [it has] significant interagency
interest.''
Response: The Technical Guidance is not a regulatory action subject
to a cost-benefit analysis under Executive Orders 12866 and 13563. The
Technical Guidance was classified as a HISA because it was novel and
precedent setting, not due to the potential financial implications. The
Technical Guidance will inform assessments of activities that occur in
a regulatory context as they arise. The Technical Guidance does not
address or change NMFS' application of the thresholds in the regulatory
context, under applicable statutes. Any required cost-benefit
considerations will take place during future actions that are the
subject of regulatory action, such as ITAs under the MMPA. The nature
and magnitude of such effects will depend on the specific actions
themselves. Because any direct effects from the Technical Guidance are
speculative and conjectural, NMFS cannot meaningfully analyze potential
effects by a cost-benefit analysis.
Comment 8: The CRE states that NMFS needs to prepare and obtain
Office of Management and Budget (OMB) approval of a new Paperwork
Reduction Act (PRA) Information Collection Request (ICR) in compliance
with Information Quality Act (IQA) Guidelines before they can use the
Technical Guidance for any sound source.
Response: There is no collection of information requirement
associated with the Technical Guidance. However, NMFS' information
collection for Applications and Reporting Requirements for Incidental
Taking of Marine Mammals by Specified Activities Under the Marine
Mammal Protection Act, OMB approval number 0648-0151, could be affected
by applicants using the Technical Guidance, possibly in added response
time to prepare applications using the Guidance. The current approval
expires in March 2017 and will require renewal before then with an
opportunity for public comment. In preparation for that renewal, NMFS
will consider the effect of the Technical Guidance, specifically
whether a revision in the burden hour estimates is appropriate, and
invite public comment on its assessment. NMFS has complied with the IQA
Guidelines with the development of the Guidance.
Comment 9: A commenter requested that NMFS provide more information
how the Guidance's updated thresholds would be applied in conjunction
with thresholds used to assess MMPA Level B behavioral harassment.
Response: The Technical Guidance does not provide updated acoustic
thresholds for levels that could result in behavioral effects. NMFS'
current acoustic thresholds for these impacts are not affected by the
Technical Guidance. NMFS recognizes the Technical Guidance provides
updated metrics that are different than those used for estimating
behavioral harassment. Accordingly, where calculations or modeling
suggest that some animals will be exposed to sound levels that are at
or above the relevant PTS threshold under the Technical Guidance but
behavioral harassment under the current behavioral harassment
thresholds, an individual should be counted ``taken'' one time, by the
more severe impact (i.e., PTS onset). However, the qualitative and
contextual analysis of the likely impacts on that animal, at these
exposure levels, will consider both the impacts of the likely PTS as
well as anticipated behavioral responses.
Comment 10: During the third public comment period, the Commission
recommended that NMFS review and revise this document every two years
via a small expert panel, as opposed to the proposed three to five year
schedule. Revising the Guidance on a two-year basis was also supported
by other commenters. Additionally, the Commission recommended that
rather than developing independent guidance, NMFS instead incorporate
by reference technical reports and peer-reviewed literature already
summarizing the best available science.
Response: NMFS will continue to monitor and evaluate new data as
they become available and will periodically convene staff from our
various offices, regions, and science centers, and to update the
Guidance as appropriate (anticipating updates to occur on a three to
five year cycle). NMFS believes this timeline is appropriate and does
not need to be modified.
[[Page 51700]]
NMFS disagrees with the Commission's recommendation to incorporate
by reference other reports or peer-reviewed literature and believes the
process of developing Technical Guidance requires a more thorough
evaluation of the science in the context of NOAA statutory
requirements. Public comment would also be needed.
Comment 11: Several commenters expressed uncertainty and requested
clarification as to how the Guidance would apply to mitigation and
monitoring requirements (e.g., exclusion zones), often prescribed by
the conditions of an MMPA permit or authorization.
Response: Mitigation and monitoring requirements associated with an
MMPA authorization or ESA consultation or permit are independent
management decisions made in accordance with statutory and regulatory
standards in the context of a proposed activity and comprehensive
effects analysis, and are beyond the scope of the Technical Guidance.
NMFS acknowledges that in practice, exclusion zones and monitoring
zones have often corresponded to acoustic impact thresholds, but that
is not a legal requirement, and the updated thresholds may make such a
simple correlation more challenging, given their greater complexity.
The Technical Guidance will be used with other relevant information to
inform impact assessments, and that in turn will be considered in the
development of mitigation and monitoring.
Peer Review Process
Comment 12: One commenter expressed concerned about the peer review
process and choice of peer reviewers, particularly in regards to
potential financial ties to NMFS.
Response: NMFS adhered to appropriate procedures in the selection
of the peer reviewers to prevent any real or perceived conflicts of
interest. The Commission, specifically their Commissioners and members
of their Committee of Scientific Advisors, nominated the peer reviewers
for each of the three peer reviews. Additionally, the Acoustical
Society of America's Underwater Technical Council nominated some of the
peer reviewers in association with the third peer review. Each peer
reviewer, for all three reviews, submitted a conflict of interest form.
None of the Technical Guidance's reviewers indicated having a conflict
of interest, defined as ``any financial or other interest which
conflicts with the service of the individual because it (1) could
significantly impair the individual's objectivity, or (2) could create
an unfair competitive advantage for any person or organization.''
Comment 13: Several commenters expressed concern that the March
2016 Proposed Changes document did not undergo peer review and believed
peer review would result in significant changes to the Guidance
necessitating the need for a fourth public comment period. If NMFS does
not conduct a fourth public comment period, the commenters advocated
that NMFS retract its March 2016 Proposed Changes document and proceed
with issuing the July 2015 Draft Guidance (modified based on public
comments from the first and second public comment period) as its
finalized Guidance.
Response: The comments are incorrect. NMFS conducted a follow-up
peer review concurrent with the third public comment period. NMFS
disagrees with the recommendation to retract the March 2016 Proposed
Changes document and that a fourth public comment period is needed
based on comments made by the peer reviewers during this follow-up
review. The follow-up peer review report is publicly available via:
http://www.cio.noaa.gov/services_programs/prplans/ID43.html and was
available before the Guidance was finalized (May 2016).
Comment 14: One commenter indicated that Guidance should not be
used until NMFS addresses all the peer reviewers' comments from its
three peer reviews, and that failing to doing so would cause the
finalized Guidance to be IQA non-compliant.
Response: NMFS adhered to IQA procedures and NOAA's IQG, making the
finalized Technical Guidance IQA compliant. NMFS received valuable
input from the peer reviewers and made changes to the Technical
Guidance based on their comments during all three peer reviews, as well
as during the follow-up review. The peer reviewers' comments greatly
improved the Technical Guidance before it was available for public
comment during the initial and second public comment periods. The
manner in which NMFS addressed the peer reviewers' comments, from all
three peer reviews, as well as the follow-up review, appear within our
Peer Review Reports: http://www.cio.noaa.gov/services_programs/prplans/ID43.html.
Comment 15: A commenter considered NMFS' treatment and peer review
of the Finneran Technical Report, associated with the July 2015 Draft
Guidance (Appendix A), as inconsistent, asserting the Finneran
Technical Report should have been treated similarly to other
publications that did not undergo formal peer review associated with
publication in a scientific journal. The commenter questioned why the
methodology from the Finneran and Jenkins (2012) technical report was
not subjected to an independent peer review by NMFS but was used in its
2013 Draft Guidance.
Response: NMFS disagrees that there was an inconsistency in its
treatment of Finneran Technical Report (the methodology used for Navy's
``Phase 3'' environmental compliance analyses in any of the versions of
our Technical Guidance. NMFS considered Finneran and Jenkins (2012) in
the development of the 2013 Draft Guidance. However, that particular
technical report served as a summary of methodology and previously
published data on impacts of sound on protected species (i.e., it did
not contain any new data). Although Finneran and Jenkins (2012) was not
published, the portions used directly in the 2013 Draft Guidance were
supported by peer reviewed publications. A separate peer review of
Finneran and Jenkins (2012) was neither necessary nor required under
HISA requirements.
For the 2015 Draft Guidance, the Finneran Technical Report, used to
derive updated marine mammal auditory weighting functions and
thresholds for the Navy's Phase 3 analyses, was directly incorporated
into the Guidance via Appendix A. This was the first time the Finneran
Technical Report was made public, and thus, was subject to HISA
requirements for inclusion in the Technical Guidance, including peer
review. We also note that after the July 2015 public comment period,
part of the Finneran Technical Report, specifically a summary of
available data on noise-induced hearing loss in marine mammals, was
published in a peer reviewed journal (Finneran et al., 2015).
Comment 16: Several commenters expressed concerns over NMFS
adopting the Finneran Technical Report within the Guidance. One
commenter specifically stated that the Guidance ``effectively results
in the US Navy writing its own regulations'' and recommended that the
entire Guidance process be reconvened using a fully independent panel
of experts.
Response: NMFS disagrees with the commenters' assessment. The
author of the Finneran Technical Report that was incorporated into
Technical Guidance (Appendix A) is a well-respected and recognized
scientist with over 50 peer reviewed publications on marine mammal
hearing and has served on the Southall et al., 2007 expert panel, as
well as the current Southall panel that
[[Page 51701]]
is updating their 2007 publication. Additionally, this methodology
underwent an independent peer review convened by NMFS and was evaluated
internally within NMFS before it was incorporated into our Technical
Guidance. NMFS believes the Finneran Technical Report represents the
best available science, which is why we incorporated it in the
Technical Guidance.
Comment 17: One commenter requested that the NMFS share their
original documents and peer reviews from the first peer review (2013),
in order to facilitate common understanding as to those aspects of
science related to marine mammal behavior that may be limiting NMFS'
ability to establish guidance and promote studies that would address
significant data gaps.
Response: As noted in the first peer review report (2013), in light
of the peer reviewers' comments and based upon internal discussions,
NMFS decided to re-evaluate its proposed methodology for deriving
acoustic thresholds for behavior and, therefore, included only
thresholds for PTS and TTS onset in the Draft Technical Guidance (i.e.,
Draft 2013 and 2015 and 2016 Proposed Changes public comment versions).
NMFS did not include peer reviewer comments on proposed behavioral
thresholds in the peer review report because they were no longer
relevant to the scope of the Draft Guidance contents. NMFS will publish
this information, if relevant, once we re-evaluate our approach for
establishing updated guidance for behavior effects.
Use of Published Versus Unpublished Data
Comment 18: Several commenters remarked on the use of published and
unpublished literature in the Guidance and sought clarification
regarding the sources considered in the development of the Guidance.
Response: Not all data considered in the development of the
Technical Guidance have been published in a peer review journal. For
the development of PTS and TTS onset acoustic thresholds and marine
mammal auditory weighting functions, NMFS primarily relied on published
data. The scientific aspects of the Technical Guidance underwent some
form of peer review, either via formal publication in a scientific
journal and/or via the HISA process.
Comment 19: Several commenters recommended that unpublished
information from more recent scientific conferences should be
considered in the Guidance. One commenter specifically indicated
Southall et al. (2007) will be updated in the near future and that the
Guidance's finalization should be delayed for this publication or NMFS
should commit to updating its Guidance within six months of the
finalization of the updated Southall et al. (2007) publication.
Response: NMFS notes that when these more recent studies become
available, they can be considered and incorporated into future updates
of the Technical Guidance. NMFS is aware that Southall et al. (2007) is
being updated. We anticipate that the methodology in the Technical
Guidance will be similar to that provided in the updated publication
(the author of the Navy's Finneran Technical Report is also on the
panel updating Southall et al., 2007). NMFS will evaluate and consider
the updated Southall et al. publication when it becomes available and
does not believe delaying the Technical Guidance is necessary.
Regarding the request to update the Technical Guidance within six
months of the updated Southall et al. (2007) publication, NMFS will
evaluate the Southall update and consider next steps at the time rather
than commit to any timeframe in advance.
Comment 20: One commenter suggested that the Verboom and
Kastelein's (2005) unpublished report, specifically the ``discomfort
threshold,'' be included for consideration in the Guidance.
Response: NMFS reviewed Verboom and Kastelein (2005) and concluded
the data are more relevant for consideration in future behavioral
effects guidance.
Sound Sources
Comment 21: Some commenters indicated that the Guidance appears to
focus on five sound sources (i.e., underwater detonations, seismic
airguns, impact pile drivers, vibratory pile drivers, and sonar). They
recommended the document consider other sound sources that have the
potential to result in noise-induced hearing loss and provide a list of
these potential sources within the Technical Guidance, so that other
sounds sources are given explicit recognition.
Response: The Technical Guidance identifies the received levels, or
thresholds, above which individual marine mammals are predicted to
experience changes in their hearing sensitivity for acute, incidental
exposure to all underwater anthropogenic sound sources. NMFS believes
providing a list of all potential sounds sources within the Technical
Guidance is unnecessary and would limit the document's utility (e.g.,
if there was a new source that was not specifically listed).
Comment 22: Multiple commenters remarked that the Guidance's
definitions of ``non-impulsive'' and ``impulsive'' sounds are vague
(i.e., NMFS does not define what is meant by ``high peak sound pressure
level'' or ``rapid rise time'') and do not objectively distinguish
between these two types of sound. The commenters recommended that
clear, technical definitions be included. Further, commenters noted
that impulsive sounds become increasingly continuous with distance, due
to multipath arrivals and other factors, and may have continuous
components even at short distances due to reverberation and requested
NMFS also consider waveform data at the location of the marine mammal
to categorize sound sources.
Response: The Technical Guidance relied on defining sound sources
based on previously established definitions and standards (i.e.,
American National Standards Institute (ANSI)). NMFS categorized sound
sources as impulsive or non-impulsive based on temporal characteristics
of the sound at the source. The definition of an impulsive sound source
in the Technical Guidance relates specifically to noise-induced hearing
loss and specifies the physical characteristics of an impulsive sound
source, which likely gives impulsive sounds a higher potential to cause
auditory injury than non-impulsive sounds. Unfortunately, these
standards do not provide quantitative definitions for terms like
``high'' peak sound pressure level and ``rapid'' rise time, especially
in the context of underwater sources.
NMFS acknowledges that sound propagation is complex and the
physical property of sounds change as they travel through the
environment. The July 2015 Draft Guidance proposed a methodology for
examining when impulsive sounds are less likely to possess the physical
characteristics that make them more injurious (i.e., peak sound
pressure level and pulse duration). This proposed methodology underwent
an independent peer review (Guidance's third peer review). However,
based on comments received during the public comment period for the
2015 Draft Guidance, NMFS decided the proposed methodology would
benefit from by further research, removed the proposed methodology from
main Guidance document, and highlighted it in the Research
Recommendations, Appendix B. Included in the Technical Guidance's
Research Recommendations is a call to identify sound characteristics
associated with injury, which may allow for more
[[Page 51702]]
detailed definitions in future iterations of this Guidance.
Comment 23: One commenter suggested that the Guidance definition of
impulsive sound sources as those with signals less than one second in
duration could possibly capture sources that are not truly impulsive
and recommended that impulsive sources be defined as those which exceed
some threshold of impulse, defined as ``the time integral of a force
over the time that the force is applied (ANSI 1994).'' Another
commenter suggested characterizing impulsive sources based on metrics
which consider rise time, crest factor, or the signal kurtosis (i.e.,
statistical quantity that represents the impulsiveness ``peakedness''
of the event). A follow-up comment acknowledged that kurtosis in the
time domain may not be practical and suggested considering kurtosis in
the frequency domain.
Response: The terms impulsive and non-impulsive as defined in the
Technical Guidance are based on several ANSI standards. If action
proponents are unclear which category their source might fit, they may
contact NMFS for further discussion. NMFS acknowledges that the
additional factors suggested by the commenters could be useful for
defining source types. However, these are not currently commonly used
descriptors by action proponents or those conducting marine mammal
noise-induced hearing loss studies (i.e., data are not typically
collected and published using these metrics), and would not be easily
implementable at this time. Additional metrics can be considered as
more data become available in a broader array of metrics. A better
understanding of appropriate metrics has been identified as an area for
recommended research in Appendix B of the Technical Guidance. In
regards to using kurtosis in the frequency domain, NMFS re-examined
this metric based on the comment received. However, upon evaluation, it
was determined that this metric is still not currently practical to
implement.
Comment 24: The Commission recommended that the 2015 Finneran
Technical Report definitions of impulsive and non-impulsive sounds be
adopted by NMFS and used in all contexts, including MMPA Level B
behavioral harassment.
Response: The Technical Guidance definitions of impulsive and non-
impulsive sounds comply with ANSI definitions and were subject to
independent peer review (third peer review). These specific definitions
were chosen to capture those physical characteristics that make a sound
more or less injurious in terms of noise-induced hearing loss. The
Technical Guidance does not address direct behavioral impacts from
sound and so does not adopt definitions that bear on behavior.
Classification of sound sources in terms of behavioral harassment will
be examined when we develop guidance for these types of impacts.
Comment 25: Multiple commenters expressed concern that seismic
waterguns produce higher frequency sounds than seismic airguns and
should not be used to set thresholds for airguns.
Response: NMFS established Technical Guidance for all impulsive
sounds based on the currently available data, which may not include
every potential sound source to which a marine mammal could be exposed.
Watergun data were used to represent airguns, as well as impact pile
driving for most hearing groups. However it should be noted that the HF
cetacean TTS onset impulsive thresholds are derived directly from data
obtained from a harbor porpoise exposed to a single airgun.
Incorporating marine mammal auditory weighting functions into exposure
models allows for the consideration that airguns predominantly produce
lower frequencies compared to waterguns.
Comment 26: A group of commenters expressed concern the Guidance
will restrict the use of marine vibrators, which are designed to be
more environmentally friendly by avoiding the generation of sound in
the ``best hearing'' range of most marine animals, and generate a
significantly lower overall sound pressure level throughout the
frequency band relative to seismic airguns.
Response: The Technical Guidance does not restrict or allow any
activity. It sets out science-based thresholds for the onset of
auditory impacts based on our evaluation and synthesis of available
data. Decisions about various sound-generating activities are outside
the scope of the Technical Guidance.
Comment 27: A commenter noted that when considering sound source
characterization, recording equipment can be limited in bandwidth and
dynamic range (i.e., equipment may not be able to accurately
characterize the sound source).
Response: NMFS agrees that fully characterizing the complete
spectrum of a sound source, within the hearing ranges of marine
mammals, is essential to accurately assess potential impacts, as is
ensuring that sources meet manufacturer specifications (i.e., sometimes
sources are capable of producing sounds outside their specified bands,
which have the potential to fall within the hearing range of marine
mammals; Deng et al., 2014; Hastie et al., 2014). This factor is
important in considering the potential of a sound source to impact a
specific hearing group, and text addressing this point has been added
to the Technical Guidance.
Comment 28: One commenter remarked that the Guidance was unclear
whether NMFS will require sound source verification (SSV), associated
with the application of the Guidance's acoustic thresholds. The comment
noted that conducting a SSV poses a complicated and unnecessary burden
on operations because the results are highly variable due to constantly
changing conditions in the environment.
Response: The Technical Guidance does not impose any such
requirements. NMFS has added text to the introduction of the Technical
Guidance to clarify this point.
Metrics
Comment 29: One commenter recommended additional clarification on
various sound metrics to prevent confusion between the peak sound
pressure level (PK) used in the current Guidance and maximum RMS SPL
used to describe prior NMFS thresholds.
Response: NMFS agrees and added clarification to the Technical
Guidance to distinguish between metrics used in this document and those
associated with previous thresholds, as well as including definitions
of these metrics in the Glossary (Appendix E).
Comment 30: One commenter requested clarity on the definition of
``peak pressure'' used in the Guidance, which the commenter assumes to
be the equivalent of a ``zero-to-peak'' value. This commenter further
indicated that the Guidance has been inconsistent in converting between
``peak-to-peak'' and RMS values to ``zero-to-peak'' values.
Response: NMFS has defined peak sound pressure level in the
Glossary (Appendix E) and has clarified the definition in the Technical
Guidance to indicate a zero-to-peak value. NOAA disagrees that there
are inconsistencies in the Technical Guidance because there have been
no conversions made between zero-to-peak and peak-to-peak sound
pressure levels or from RMS sound pressure to any other metric anywhere
in this document.
Comment 31: To match what was provided in the Finneran Technical
Report (Appendix A of July 2015 Draft Guidance), the Commission and
some other commenters recommended that NMFS only provide dual metrics
for PTS onset for impulsive sources (i.e.,
[[Page 51703]]
remove peak pressure metric threshold for non-impulsive sources).
Conversely, a commenter was not supportive of removing the peak
pressure thresholds for non-impulsive sources, as was suggested in the
2016 Proposed Changes document. Finally, there was some confusion as to
how and when the PK threshold needs to be considered based on the
updates in the 2016 Proposed Changes document.
Response: Upon further evaluation, NMFS agrees and has removed the
PK thresholds for non-impulsive source in the Technical Guidance, since
it is highly unlikely that the dominant metric for non-impulsive
sources will be the peak sound pressure level. However, the Technical
Guidance caveats that if a non-impulsive sound has the potential of
exceeding the PK threshold associated with impulsive sources, these
thresholds should still be considered. Thus, in the Technical Guidance,
there remain dual criteria associated with impulsive sources (i.e.,
applicant should consider whichever threshold results in the largest
effect distance (isopleth)).
Comment 32: A few commenters remarked SELcum is not a
standardized acoustic notation and that the Guidance should adhere to
existing standards in terms of terminology, definitions, symbols, and
acronyms in order to promote clarity and reduce confusion. It was also
recommended that NMFS work with standards-setting bodies to develop a
consistent system of notation for marine bioacoustics applications
(e.g., ANSI or International Organization for Standardization (ISO)).
Response: NMFS acknowledges that neither the 2013 nor the 2015
Draft Guidance documents consistently used notations complying with
available standards. The final Technical Guidance has been revised to
better reflect ANSI standards (e.g., terminology, abbreviation, and
symbols). Further, NMFS is aware of the work of ISO 18405 to develop
standards specifically for underwater acoustics and will re-evaluate
the Guidance's notations in future updates once the ISO work becomes
finalized.
Comment 33: One commenter noted an inconsistency in the Guidance
with both PK and SELcum acoustic thresholds being derived
from the same study. The commenter noted that if the energy from a
transmission does not cause an impact at a given frequency because of
an animal's reduced sensitivity (or capability) to hear that signal,
then the ability to be impacted by the PK should also be reduced for
that frequency.
Response: NMFS does not agree there is an inconsistency in how data
were assessed. Data from Lucke et al. (2009) were used to derive both
thresholds for HF cetaceans exposed to impulsive sources. For MF
cetaceans, both thresholds come from belugas exposed to waterguns
(Finneran et al., 2002). For both the Lucke et al. (2009) and Finneran
et al. (2002) study, TTS onset was recorded in multiple metrics, with
two of these metrics (i.e., PK and SELcum) directly used in
the Technical Guidance. NMFS disagrees that auditory weighting
functions are appropriate for use with the PK metric, as direct
mechanical damage associated with sounds having high peak sound
pressures typically does not strictly reflect the frequencies an
individual species hears best (i.e., why PK thresholds should be
considered unweighted/flat-weighted within the entire frequency band of
a hearing group).
Comment 34: Multiple commenters noted that the SELcum
metric within the Guidance is used under the assumption that a low
amplitude/long signal having an equal SELcum, as a high
amplitude/short signal, will have the same effects on the auditory
system (i.e., the Equal Energy Hypothesis (EEH)). A commenter further
stated that the EEH may be correct in certain conditions, but that an
increasing body of evidence indicates that the EEH does not hold true
for most marine mammal sound exposures. It was suggested that as more
data become available, NMFS should perform more analyses to determine
what model or equation best fits the EEH and revise the acoustic
thresholds to more accurately reflect the potential for TTS changes
with duration and amplitude.
Response: NMFS agrees that EEH may not be valid for all exposure
situations. However, the Technical Guidance provides acoustic
thresholds in the SELcum metric, based on the belief that
the EEH is the best means of incorporating this metric (also
recommended by Southall et al., 2007). NMFS maintains that despite the
shortcomings, having a metric that includes the duration of exposure is
critical for predicting effects of noise on marine mammal hearing. The
evaluation of appropriate metrics and EEH has specifically been
identified as an area where more research is needed (Guidance Appendix
B).
Comment 35: One commenter indicated since ``SEL'' is the
accumulated acoustic energy in a signal and cumulative by definition,
whether calculated over one second or a single pulse event, the
Guidance's use of ``SELcum'' to describe cumulative sound
exposure is unnecessary. The commenter suggested NMFS should simply use
the abbreviation ``SEL''.
Response: NMFS agrees that the SEL implies accumulation. The ANSI
definition indicates that accumulation occurs over a stated time
interval, which is typically referenced to one second. In order to
clarify that the duration of accumulation in the Guidance is not one
second (i.e., 24 hours), NMFS chose to use the notation
SELcum.
Use of Data From Captive Marine Mammals
Comment 36: Multiple commenters indicated that the use of data from
captive individuals was a poor proxy (e.g., over-estimate TTS onset or
hearing thresholds, may be habituated or have different survival
tactics) for their free-ranging counterparts and suggested that data
from captive bottlenose dolphins be adjusted to be more representative.
Response: NMFS acknowledges that captive individuals may be
habituated to their test environment, making them less than ideal
proxies for their free-ranging counterparts for studying behavioral
reactions to noise. However, we believe habituation has minimal effects
on testing auditory capabilities and the impacts of noise on hearing,
which is the focus of this Technical Guidance.
For example, NMFS notes that data from Castellote et al. (2014),
from free-ranging belugas in Alaska, indicate of the seven healthy
individuals tested (3 females/4 males; 1 subadult/6 adults), all had
hearing abilities ``similar to those of belugas measured in zoological
settings.'' Thus, from this one study, it appears that for baseline
hearing measurements, captive individuals might be an appropriate
surrogate for free-ranging animals. However, this is currently the only
study of its kind, and more research is needed to examine if this trend
applies to other species (see Appendix B: Research Recommendations).
NMFS also finds an adjustment to bottlenose dolphin data is
unnecessary. The Technical Guidance methodology for deriving marine
mammal auditory weighting functions incorporates data from a multitude
of species (~20 species), beyond just bottlenose dolphins, and is
considered representative based on the best available science.
Comment 37: Several commenters expressed concern over the ages of
many of the captive individuals used in TTS studies as not being
representative (e.g., thresholds obtained from younger bottlenose
dolphin in Johnson 1968 are on average 10 dB lower than from older
individuals) and considers them sources of uncertainty. Many commenters
suggested that data from older
[[Page 51704]]
individuals should either be adjusted or excluded from consideration.
Response: NMFS disagrees that data from older individuals needs to
be excluded or adjusted and notes that Houser and Finneran (2006) did a
comprehensive study on the hearing sensitivity of the Navy bottlenose
dolphin population (i.e., tested 42 individuals from age 4 to 47 years;
28 males/14 females) and found that high-frequency hearing loss
typically began between the ages of 20 and 30 years. For example, at
frequencies where this species is most susceptible to noise-induced
hearing loss (i.e., 10 to 30 kilohertz (kHz)), these are the
frequencies where there is the lowest variability in mean thresholds
between individuals of different ages. Additionally, for harbor seals,
similar levels of TTS onset were found in Kastelein et al. (2012a) for
individuals of 4 to 5 years of age compared to the individual from in
Kastak et al. (2005), which was 14 years old. For belugas similar
levels of TTS were measured in Popov et al. (2014) for an individual 2
years old compared to those used in Schlundt et al. (2000), which were
20 to 22 years old or 29 to 31 years old.
Further, Houser and Finneran 2006 attribute the lower thresholds
recorded by the individual from Johnson (1968) to differences in
methodology (i.e., Johnson (1968) used behavioral protocol to test
hearing versus electrophysiological methodology by Houser and Finneran
(2006)). The Technical Guidance relies primarily on behavioral data
associated with hearing and threshold shift measurements, as opposed to
those obtained via other means (e.g., auditory evoked potentials (AEP))
because we consider these data to be most representative of hearing
ability and noise-induced hearing loss, which further eliminates the
need for any adjustment.
Comment 38: One commenter indicated that studies show that marine
mammals tend to avoid disruptive sound sources, which could
significantly diminish the potential for noise-induced hearing loss.
Therefore, the commenter suggests that the data collected in laboratory
experiments are likely to result in overestimates of exposure because
the subjects are exposed to longer and louder sounds than they would be
in the natural environment.
Response: NMFS agrees that when considering exposure durations for
animals under realistic exposure conditions, generally, it is predicted
that most individuals will only be in the closest ranges to a sound
source/activity for a minimal amount of time (e.g., animals are capable
of moving horizontally and vertically in the water column to reduce
exposure, and/or individuals are exposed to mobile sources). Thus,
using laboratory data from animals exposed to unusually long,
continuous durations of sound (i.e., animals cannot leave exposure
scenario and the level during exposure remains constant) may not best
reflect scenarios expected to be encountered by wild individuals, when
exposed to sound over long periods of time. However, measurements of
TTS from laboratory studies are the only data currently available, and
they remain informative regarding sound exposure that may impact marine
mammal hearing. Appendix B of the Guidance recommends future TTS
studies to address exposures animals are likely to receive in the
natural environment and provide more representative results.
Marine Mammal Hearing Ranges
Comment 39: One commenter noted that the establishment of hearing
groups is fundamentally flawed because it is based on the assumption
that similar exposures will result in similar effects in all group
members. The commenter believes it is important to consider species
differences in behavior (e.g., movement away from the noise source)
when calculating cumulative exposure associated with PTS onset.
Response: NMFS agrees that marine mammal behavioral responses could
result in differences in noise exposures and accumulation scenarios
(i.e., SELcum). However, NMFS disagrees that such responses
necessarily indicate that hearing physiology is dissimilar or that
levels causing noise-induced threshold shifts are dissimilar between
species within a hearing group. Further, differences in behavioral
responses to sound will be considered in the development of behavioral
effects thresholds.
Comment 40: One commenter indicated that the method for determining
the limits of the functional hearing ranges was not clearly indicated
in the Guidance and suggests that NMFS should indicate how the limits
were obtained for each group. Another commenter indicated that the term
``functional hearing range'' is intended to convey the range over which
the majority of the species' hearing ability is found. However, there
are at least two examples of a species' ability to hear a signal
outside its functional hearing range (i.e., false killer whale and
Risso's dolphin (Au et al., 1997)).
Response: Based on the revised methodology for establishing marine
mammal auditory weighting functions (Appendix A), NMFS has replaced the
concept of functional hearing range with the establishment of what the
Technical Guidance terms ``generalized hearing range'' for each hearing
group. The latter is recommended for consideration associated with flat
weighting for PK thresholds and when determining general risk of
auditory impacts from noise. The generalized hearing ranges were chosen
based on the approximate 65 dB threshold from the normalized composite
audiogram. NMFS believes that outside the generalized hearing range,
the risk of auditory impacts from sounds (i.e., TTS or PTS) is
considered to be either zero or very low (the exception would be if a
sound above/below this range was determined to have the potential to
cause physical injury, i.e., lung or gastrointestinal tract injury from
explosives) and added additional information to clarify this in the
Technical Guidance.
NMFS is aware of the Au et al. (1997) paper, which examines the
effect of the 75 Hz acoustic thermometry of ocean climate (ATOC) signal
on hearing sensitivity of a single false killer whale and single
Risso's dolphin, both mid-frequency (MF) cetaceans. Hearing thresholds
for both species, from this study, were 139 dB or higher (false killer
whale: Thomas et al., 1988; Risso's dolphin: Nachtigall et al., 1995).
Thus, this ATOC signal is considered beyond the generalized hearing
range of MF cetaceans.
Comment 41: Several commenters questioned the justification used to
support the PW and OW pinnipeds' upper hearing limit in the Technical
Guidance. The commenters noted that newer studies have consistently
shown that 75 kHz is a more reasonable upper cutoff for PW pinnipeds
underwater. These commenters recommended that NMFS choose the median
value, not the most conservative value, for the PW pinniped upper
hearing range limit. For OW pinnipeds, the 2013 Draft Guidance does not
clearly explain why 40 kHz was selected as a high-frequency cut-off for
OW pinnipeds instead of 50 kHz reported in Finneran and Jenkins (2012).
Response: As indicated in the previous comment/response, NMFS has
provided generalized hearing ranges by marine mammal hearing group. The
generalized hearing ranges are supported by available pinniped
audiogram data that were used to derive the composite audiogram for
this group (Terhune 1988; Kastak and Schusterman 1999; Kastelein et
al., 2009; Reichmuth et al., 2013; Sills et al., 2014; and Sills et
al., 2015). The generalized frequency ranges are intended to be broad
enough to encompass the hearing range of the
[[Page 51705]]
entire hearing group (i.e., choice of using 65 dB threshold compared to
60 dB threshold typically used to define human and other terrestrial
mammal hearing ranges). Thus, NMFS disagrees that using a median is
preferred. For PW and OW pinnipeds, the upper range based in the
finalized Technical Guidance is 86 kHz and 39 kHz, respectively.
Comment 42: One commenter noted that current ESA and MMPA analyses
are based on data collected while monitoring previous activities, with
little of that data having been analyzed by hearing group. The
commenter suggested that until more data are available, it will be
difficult to find data upon which to base the analyses.
Response: NMFS disagrees that it will be difficult to complete
analyses and believes that hearing group data and marine mammal
auditory weighting functions provided in the Technical Guidance are
based on the best available science and can be applied to any source.
Additionally, the Technical Guidance states that the application of
marine mammal auditory weighting functions should be completed after
data collection (i.e., auditory weighting functions should not be
applied beforehand), with the total spectrum of sound preserved for
later analysis (i.e., if weighting functions are updated or if there is
interest in additional species, data can still be used).
General Auditory Weighting Functions
Comment 43: NMFS' exclusion of AEP data in establishing marine
mammal composite audiograms and auditory weighting functions was
criticized by several commenters. These commenters noted that by
including AEP datasets, the statistical power of the assessment would
be improved.
Response: In deriving marine mammal composite audiograms, NMFS
established an informal data hierarchy in terms of assessing these
types of data. Specifically, audiograms obtained via behavioral
methodology provide the most representative presentation (most
sensitive) on hearing ability, followed by AEP data, lastly by
mathematical models for species where no data are available (i.e., low-
frequency or LF cetaceans). Thus, the highest quality data available
for a specific hearing group should be used, which for all hearing
groups, except LF cetaceans, is behavioral. Additional clarifying text
on this informal data hierarchy has been provided in the Technical
Guidance.
It also should be noted that marine mammal AEP audiograms have been
based almost exclusively on measurements of the auditory brainstem
response, and thus do not take into account contributions to hearing
from higher centers of the brain and auditory nervous system, and no
means have been established for ``correcting'' AEP data so that they
may be more comparable to those obtained via behavioral methods. AEP
thresholds are typically elevated compared to behavioral thresholds in
a frequency-dependent manner, especially at lower frequencies (e.g.,
Szymanski et al., 1999; Yuen et al., 2005; Houser and Finneran 2006);
therefore including the low-frequency AEP data in the composite
audiogram would cause an artificial increase in audiogram low-frequency
slope and cause the resulting weighting function to be more narrow at
low frequencies.
Despite not directly including AEP audiograms in the development of
a hearing groups' composite audiogram, these data were evaluated to
ensure species were placed within the appropriate hearing group and to
ensure that a species for which only AEP data were available were
within the bounds of the composite audiogram for that hearing group.
Further, AEP TTS data are presented within the Guidance for comparative
purposes alongside TTS data collected by behavioral methods
illustrating that the AEP TTS data are within the bounds (the majority
of the time above) of those collected by behavioral methods (i.e.,
Figures A18 and A19).
Comment 44: One commenter remarked that the Guidance may change as
improved information becomes available, which means that auditory
weighting functions may also change. The commenter suggested that NMFS
develop a mechanism for allowing updates until a widely-accepted
weighting procedure for marine mammals is standardized by expert
consensus (e.g., through the ANSI or ISO standardization processes).
Response: NMFS agrees that as additional data become available, the
auditory weighting functions, among other factors, may require
modification. For that reason, NMFS has added specifications to the
Technical Guidance indicating that auditory weighting functions should
be applied after data are collected (i.e., during data collection, the
complete spectrum of sound should be collected) to ensure they are
available for re-analysis if updated weighting functions become
available. The Technical Guidance also establishes protocols for
evaluating new data and updating the document.
Comment 45: Multiple commenters noted that each of Guidance's
hearing groups contains species whose sound production and regions of
best hearing sensitivity do not overlap to a high degree. A few
commenters further added that applying results from one or two aging
bottlenose dolphins to all members of a hearing group is inadequate.
Response: The auditory weighting functions are meant to assess risk
of noise-induced hearing loss and not necessarily encompass the entire
range of best hearing for every species within the hearing group. NMFS'
use of auditory weighting functions is consistent with how weighting
functions are used in human noise standards, which is to assess the
overall hazard of noise on hearing. Specifically, the human auditory
weighting function provides a ``rating that indicates the injurious
effects of noise on human hearing'' (OSHA 2013). While these weighting
functions are based on regions of equal loudness and best hearing, they
are meant to reflect the susceptibility of the ear to noise-induced
threshold shifts, and as such, the region of enhanced susceptibility to
noise exposure may not perfectly mirror a species' region of best
hearing (e.g., TTS data from bottlenose dolphin, belugas, and Yangtze
finless porpoise support this).
Further, updated methodology in the July 2015 revised Draft
Guidance used composite audiograms based on multiple species to derive
marine mammal auditory weighting functions. Thus, data from more than
just bottlenose dolphins were used to derive these functions (i.e., MF
cetacean composite audiograms are derived using data from eight
different species).
As for how animal age could impact hearing susceptibility, please
see Response to Comment 37.
Comment 46: Multiple commenters expressed concern that the
Guidance's marine mammal auditory weighting functions are invalid,
since they are based on assumptions that have not been subject to
uncertainty analysis for frequencies below 3 kHz.
Response: NMFS disagrees that there is greater uncertainty for
frequencies below 3 kHz, since audiogram data were collected for
frequencies below 3 kHz for a multitude of species in the MF and HF
cetacean and PW and OW pinniped hearing groups (e.g., see Figure A5 in
Technical Guidance). Further, low-frequency data from the composite
audiogram is used to directly determine the slope of the weighting
function.
Comment 47: A commenter requested clarification on what NMFS
intended by the term ``smaller isopleth'' in discussing the effects
marine mammal
[[Page 51706]]
auditory weighting functions have on exposure modeling results.
Response: The Technical Guidance thresholds associated with a
hearing group themselves do not change depending on how much a sound
may overlap a group's most susceptible frequency range. Instead, how
weighting functions affect exposure modeling/analysis is related to the
size of the isopleth (area) associated with the threshold based on how
susceptible that particular hearing group is to the particular sound
being modeled. For example, a hearing group could have different size
isopleths associated with the same threshold, if one sound was within
its most susceptible frequency range and the other was not (i.e., sound
in the most susceptible hearing range will result in larger isopleth
compared to sound outside the most susceptible hearing range). We have
provided additional text in the Technical Guidance to clarify this
concept.
Comment 48: One commenter expressed concern as to the practicality
of obtaining and maintaining modeled sound field results for broadband
sources (e.g., airguns or impact pile drivers) in order for weighting
functions (current or revised) to be applied at a later date.
Response: The Technical Guidance recommends that marine mammal
auditory weighting functions be applied after sound field measurements
have been obtained (i.e., post-processing; auditory weighting functions
should not be applied beforehand), with the total spectrum of sound
preserved for later analysis (i.e., if weighting functions are updated
or if there is interest in additional species, data can still be used).
This recommendation applies to actual field measurements and not
modeling results. The final Technical Guidance includes additional text
to clarify this point.
Uncertainty and Statistical Analyses Associated With Auditory Weighting
Functions
Comment 49: Several commenters expressed concern about uncertainty
in the development of the marine mammal auditory weighting functions
and acoustic thresholds, especially because of the reliance on mean and
median values without reporting variation (i.e., methodology does not
account for variability/confidence intervals associated with small
sample sizes). Alternative methodologies to account for uncertainty
were suggested for consideration (e.g., inverse Bayesian formulations
with Markov-chain Monte Carlo and Metropolis-Hastings sampling methods;
Wright 2015; Potential Biological Removal (PBR); human noise standards
(NIOSH 1998)).
Further, Wright (2015) claimed that inconsistencies within the
methodology used to establish the auditory weighting functions and
acoustic thresholds contributed to uncertainty; namely, that: (a) The
hearing threshold (audiogram)-to-TTS onset component, on a per
individual basis, is neglected (recommends calculating audiogram-to-TTS
onset for each individual); (b) it is inappropriate for non-adjusted
(non-normalized) TTS onset data points for individuals to be fit to
composite audiograms; and (c) there is a discrepancy between the
frequency of best sensitivity for the composite audiogram and exposure
function, which results in the weighting/exposure function gain
parameters (i.e., parameters ``K'' and ``C'') underestimating TTS
onset.
Finally, it was requested that NMFS (1) provide the underlying data
used to derive the weighting functions so that uncertainty and
statistical analyses can be evaluated by those outside NMFS and (2)
delay the Guidance's finalization until this outside process can be
completed.
Response: NMFS acknowledges the small sample size associated with
the available marine mammal data used to derive weighting functions and
thresholds presents challenges. However, the Technical Guidance's
methodology is designed to predict the mostly likely (realistic)
outcome using the central tendencies (means/median) associated with the
best available science. The intent is not to predict the worst-case-
scenario by relying on the lowest limits for every possible step in the
methodology (i.e., Technical Guidance is for accurately predicting
exposures and not for establishing ``safe limits,'' where there is
limited to no risk). Despite not using statistical methodology to
report variability, Appendix A provides the full suite of available
data for consideration and comparison to the values used in the
Technical Guidance (e.g., Figures A5 and A6 for audiogram data and
Figures A18-A20 for TTS data). With respect to data used to derive
composite audiograms, auditory thresholds are typically defined by the
50 percent detection threshold (ANSI 2009), and equal loudness contours
used to derive human weighting functions are derived using averages
(e.g., Fletcher and Munson 1933), as opposed to relying on the lowest
value (i.e., there is a precedence for using medians/means).
Additionally, it is important to remember that the derived weighting
functions are based on more than the just the composite audiogram
(i.e., the audiogram shapes are adjusted to best fit the existing TTS
data) resulting in a function that is always broader than the composite
audiogram (e.g., Figure A17).
Human noise risk assessments (NIOSH 1998) are not equivalent (or
applicable) to thresholds provided in the Technical Guidance, since
they are used to predict hearing loss based on a daily 8-h exposure
over 40 years (i.e., current marine mammal TTS are only available to
predict exposure periods of 24 h or less and cannot be used to assess
or predict risk associated with a lifetime of exposure; See Response to
Comment 79) and are based on larger sample sizes of human listeners
(e.g., NIOSH 1972 and 1997 risk assessments were based on a sample size
of 1,172 people). As pointed out in Wright 2015, NIOSH criteria provide
a 95 percent confidence interval for their human noise standards but
also allows for an excess risk of material hearing impairment, defined
as an average threshold elevation for both ears that exceeds 25 dB, of
eight percent (i.e., human noise standards limits do allow for some
risk; risk is not zero percent and specifically that eight percent of
the population is still capable of developing noise-induced hearing
loss exceeding 25 dB when exposed to the 85 dB NIOSH level). For how
the Technical Guidance's TTS thresholds encompass available data, see
Response to Comment 72 and Appendix A, Figures A18-A20, which provide
all available marine mammal TTS data collected via both behavioral and
AEP techniques). Additionally, methodology associated with the
calculation of PBR (i.e., use of twentieth percentile) was based on
simulations specific to a particular dataset (Wade 1998) and is not
applicable to the Technical Guidance.
With respect to specific comments made in Wright (2015), NMFS
disagrees there are inconsistencies in the methodology in the Technical
Guidance. Specifically related to the assertion in part (a) of the
comment that NMFS neglected the hearing threshold (audiogram)-to-TTS
onset component: In re-examining available data sets, in terms of
offset between hearing threshold and TTS onset, only six individuals
(three MF cetacean, one OW pinniped, and two PW pinnipeds) have
measurements available for both hearing threshold and TTS onset.
Differences in TTS onset at frequency of best hearing (from the
exposure function) and threshold at frequency of best hearing (from the
composite audiogram) are reflected by hearing group in the Technical
Guidance in Table A7 (Appendix A, ``Difference'' column).
[[Page 51707]]
Unfortunately, comparisons between the difference hearing thresholds
and TTS onset from the same individual to differences depicted in Table
A7 are difficult, since none of the individual TTS data occur in the
frequency of best hearing. However, TTS onset (SELcum
metric) predicted from the exposure function is within 1 dB or lower
compared to TTS onset based on these five individuals. Further, this
specific recommendation from Wright (2015), to consider data from
individual audiograms, counters other recommendations made elsewhere in
that paper that data from the same species should be considered
correlated and combined to reduce issues associated pseudoreplication
(See Response to Comments 53).
As for non-adjusted TTS data points being fit to normalized
composite audiograms (point b), the Guidance's methodology examines the
best fit of TTS data points to both original (non-normalized) and
normalized composite audiogram data to establish the ``delta T''
parameter (i.e., both non-normalized and normalized data are used to
derive delta T). Additionally, the ``K'' parameter is derived using the
original (non-normalized) audiogram data and is defined to minimize the
square error between the exposure function and TTS data for each
hearing group.
As to point (c), NMFS acknowledges that there is a shift
(discrepancy) in frequency between the best sensitivity in terms of the
composite audiogram and resulting exposure function for a hearing
group, but disagrees that this leads to an underestimation of TTS
onset. Any difference in minimum value between the exposure function
and audiogram is an outcome of the fitting process used to fit the
exposure function to the available TTS data, and thus, reflects the
underlying TTS data. This shift in minimal value results in an
identical (PW and OW pinnipeds) or lower TTS onset threshold (MF and HF
cetaceans) than predicted by considering the composite audiogram alone
(See Table A7 vs. A8 in Technical Guidance). Further, the ``C''
parameter results in a minimal adjustment to the final TTS onset
threshold (maximum 1 dB; See Table A8 in Appendix A).
Finally, NMFS believes it is unnecessary to provide underlying
datasets associated with the Technical Guidance and delay publication,
since the majority of the underlying data (with a few exceptions) are
published and freely available.
Comment 50: Commenters indicated that sound reception is an
essential ability of marine mammals, particularly cetaceans, for
survival, and these commenters, citing Nowacek et al. (2007), indicated
that PTS can lead in many cases to mortality of individuals which may
have serious consequences for the survival of populations.
Response: NMFS agrees that the ability to accurately interpret the
surrounding environment via hearing is essential for marine mammals.
However, NMFS' review of Nowacek et al. (2007) as well as all other
available information did not locate any statements that PTS can result
in mortality.
Comment 51: Some commenters recommended that audiograms from
individuals of the same species should be treated as correlated in the
determination of composite audiograms. Further, in order to determine a
conservative representative sensitivity for each hearing group, the
highest measured sensitivity, lowest threshold (behavioral or AEP), per
frequency per species should be assessed. Commenters indicated that
this would be a more cautionary approach than relying on the mean.
Response: NMFS does not disagree that audiograms from individuals
of the same species may be correlated but disagrees with the
recommendation to collapse available audiograms, so that there is only
one per species. Employing this recommendation would further reduce
already limited data sets (see Response to Comment 53 regarding
pseudoreplication recommending a similar procedure and similar issue
with data limitations) For NMFS' response relating to the use of AEP
data, see Response to Comment 43, and for our response regarding
relying on the lowest threshold, see Response to Comment 49. NMFS
believes that the Guidance's current approach maximizes the use of the
best available science.
That said, based on this comment, NMFS re-evaluated AEP data
available for consideration in the development of composite audiograms.
The inclusion of AEP resulted in only minimal changes to the composite
audiogram (i.e., majority of AEP audiogram data had equal, if not
higher thresholds, than those collected by behavioral methods, which
would only result in a less conservative composite audiogram).
Comment 52: Based on Wright 2015, commenters recommended that NMFS
develop marine mammal auditory weighting functions based on envelope
functions, which incorporate all available audiogram points.
Additionally, these same commenters objected to NMFS' comparison
between the Guidance's weighting functions and inverted audiograms
(i.e., Guidance's weighting functions are broader than inverted
audiograms that have been suggested). The commenters stressed that
inverted audiograms have only been recommended for individual species
and not entire hearing groups.
Response: NMFS disagrees with this recommendation (See Response to
Comment 49). As far as comparing the Technical Guidance's weighting
functions to inverted audiograms, NMFS agrees that the comparison to
inverse audiograms may not have been applicable and removed it from the
Technical Guidance. Nevertheless, the point that the Technical Guidance
auditory weighting functions are broader than the corresponding hearing
group's composite audiogram, as well as any audiogram associated with
an individual species, is still valid.
Comment 53: Pseudoreplication was highlighted as a significant
deficiency of the Guidance by several commenters. It was recommended
that NMFS evaluate TTS on a species-by-species basis, rather than on an
individual basis.
Response: NMFS understands the concerns regarding
pseudoreplication. However, marine mammal hearing and noise-induced
hearing loss data are limited, not only in the number of species but
also in the number of individuals available. Unfortunately, any means
of minimizing pseudoreplication would further reduce these already
limited data sets. Specifically, with marine mammal behavioral TTS
studies, behaviorally-derived data are only available for two MF
cetacean species (i.e., bottlenose dolphin, beluga) and two PW pinniped
species (i.e., harbor seal and northern elephant seal), with OW
pinnipeds and HF cetaceans only having behaviorally-derived data from
one species. Thus, NMFS believes that the current approach makes the
best use of the given data (See Response to Comment 72 for more
information on the inclusion of available TTS data). Appropriate means
of reducing pseudoreplication may be considered in the future, if more
data become available.
Comment 54: Several commenters requested that a list of data gaps
and research recommendations should be included in the Guidance to
inform funding groups and the research community of critical data
needs.
Response: NMFS agrees and has identified several data gaps and
added a Research Recommendations Appendix (B) to the Technical
Guidance.
Low-Frequency Cetacean Hearing and Auditory Weighting Functions
Comment 55: Several commenters questioned the justification for
[[Page 51708]]
expanding the upper hearing limit of LF cetaceans beyond that proposed
in Southall et al. (2007) in the 2013 Draft Guidance (i.e., 22 kHz to
30 kHz).
Response: NMFS has replaced the use of functional hearing range
with generalized hearing range, which is derived based upon more
consistent methodology (See Response to Comment 40).
Comment 56: One commenter indicated that recent data suggest that
within the LF cetacean hearing group, new divisions are appropriate to
consider (e.g., Ultra Low: blue and fin whales; Low: bowhead and right
whales; Low to Mid: humpback and gray whales; and Mid: minke whale
groups).
Response: NMFS acknowledges that as more data become available,
marine mammal hearing ranges may warrant modification, or that it may
be appropriate to divide LF cetaceans into subdivisions. However, NMFS
does not believe there currently are enough data to support further LF
cetacean divisions and subsequent auditory weighting functions,
especially since so little direct information on hearing is available
for this hearing group.
Comment 57: Several commenters questioned the sufficiency of data
to support the LF cetacean auditory weighting function provided in
various versions of the Draft Guidance. Some recommended using the M-
weighting function provided by Southall et al. (2007) until more data
could be collected or developing a LF cetacean weighting function based
on the known low-frequency vocal range of this hearing group, ensuring
that the weighting function encompasses ultra-low-frequencies (i.e.,
<30 Hz) used by blue and fin whales. One commenter further suggested
that the LF cetacean weighting function be flat down to 0 Hz to ensure
low-frequency sound does not compromise critical communication signals.
Counter to those recommendations, other commenters expressed
concern that the low-frequency slope parameter (``a'' parameter) of the
LF weighting function (i.e., 20 dB/decade) was not scientifically
supportable and should be more reflective of mammalian data (30 to 40
dB/decade). Furthermore, the selection of this parameter was criticized
because it resulted in an exposure function that predicts an
unrealistically low-frequency hearing (80 dB threshold above best
hearing occurring well below 1 Hz; e.g., only a -26 dB weighting
function amplitude at 10 Hz), which is not reflective of what is known
about other low-frequency specialist mammals, like humans and kangaroo
rats. Additionally, these same commenters commended NMFS for not using
vocalizations, especially frequencies associated with blue and fin
whales, as a direct means for deriving the LF cetacean predicted
audiogram.
Finally, NMFS received a comment from a group of subject matter
experts offering information on ambient noise levels below 2 kHz from
Clark and Ellison (2004) as additional scientific justification for the
LF cetacean weighting function contained in the March 2016 Proposed
Changes.
Response: NMFS acknowledges the limited data predicting LF cetacean
hearing sensitivity but disagrees that utilizing the M-weighting
functions from Southall et al. (2007) or creating a weighting function
that is flat to 0 Hz reflects the best available science. Via the
Technical Guidance public comment and peer review processes, NMFS
determined that the methodology in the March 2016 Proposed Changes
document best reflects the currently available data for deriving marine
mammal auditory weighting/exposure functions, including those methods
to derive surrogate parameters for LF cetaceans.
Regarding the appropriateness of using vocal range to establish
weighting functions, see Response to Comment 45. As for the frequencies
used by fin and blue whales, NMFS acknowledges that the weighting
function amplitude is >-16 dB at frequencies below 30 Hz. However,
predicted hearing sensitivity for LF cetaceans based on ambient noise
levels from Clark and Ellison (2004) offer additional scientific
support to NMFS' weighting function below 2 kHz (for direct comparison
to the 2016 LF cetacean weighting function see: https://www.regulations.gov/#!documentDetail;D=NOAA-NMFS-2013-0177-0155).
Additionally, Cranford and Krysl (2015) predicted that since low-
frequency sound propagates further than those containing higher
frequencies, this might explain the potential mismatch between the
frequencies associated with best hearing and vocalizations for LF
cetaceans. Furthermore, creating a weighting function to ensure
communication signals are not compromised is beyond the scope of this
document (the Technical Guidance weighting functions are meant to
reflect a hearing group's susceptibility to noise-induced hearing
loss).
As for the low-frequency slope associated with the LF cetacean
weighting function, NMFS believes it is reflective of currently
available predictive data for this hearing group. For example,
predictive audiograms based on anatomical modeling for minke whale
(Tubelli et al., 2012), fin whale (Cranford and Krysl 2015), and
humpback whale (Houser et al., 2001) all indicate this hearing group
may have a shallower low-frequency slope compared to other terrestrial
and marine mammals. Specifically, Tubelli et al. (2012) offers that the
``extra'' 20 dB difference in the low-frequency slope between other
cetaceans (HF and MF cetaceans) may be a result of the inner ear
anatomy of this hearing group (i.e., open auditory bulla and the
resulting pressure differences along the ``glove finger''). Finally,
ambient noise levels with slopes ~20 dB/decade support the predicted
low-frequency slope for this hearing group (Wenz 1962).
Comment 58: Multiple commenters indicated the LF cetacean exposure
function's ``K'' parameter, which the commenters classified as a metric
of dynamic range, was arbitrary and inappropriately based on data from
a beluga and a harbor porpoise for impulsive sounds.
Response: NMFS disagrees with the commenters' classification of the
exposure function's ``K'' parameter as a metric of dynamic range and
the criticism. This parameter is set to match the weighted threshold
for TTS or PTS onset based on available data in the SELcum
metric (i.e., NMFS' dynamic range methodology is for deriving PK
thresholds; See Response to Comment 87). NMFS agrees that for impulsive
sounds, TTS data are extremely limited (i.e., beluga data from Finneran
et al. (2002) and harbor porpoise data from Lucke et al. (2009)).
Nevertheless, the methodology for establishing a surrogate value for
this parameter for hearing groups where no data are available is
consistent with the derivation of other surrogate parameters within the
Technical Guidance.
Comment 59: Numerous commenters, including the Commission,
identified an inconsistency in how NMFS derived the ``F2'' parameter,
which predicts the high-frequency portion of the composite audiogram
for LF cetaceans. Specifically, this parameter was adjusted to achieve
a threshold at 30 kHz of 40 dB relative to the lowest threshold.
However, in earlier discussions of the low-frequency parameter ``F1,''
the March 2016 Proposed Changes document mentioned predictive modeling
of LF cetacean hearing indicating 40 dB of best sensitivity occurring
at ~25 kHz (i.e., not 30 kHz). Commenters were unclear if this was an
error or if 30 kHz was chosen deliberately and if so, why.
Response: NMFS acknowledges the potential for confusion and chose
to
[[Page 51709]]
adjust the ``F2'' parameter to achieve a threshold value at 30 kHz of
40 dB relative to the lowest threshold as a means to account for
uncertainty associated with this hearing group and to avoid too gradual
of a cutoff at the high-frequency end (i.e., decision to adjust
parameter at 30 kHz vs. 25 kHz). Additional text was added to the final
Technical Guidance for more clarity on this decision.
Comment 60: Numerous commenters criticized the potential for
``takes''/isopleths/mitigation ranges to increase dramatically based on
updated weighting functions/thresholds for LF cetacean hearing group
(i.e., comparison between 2015 Draft Guidance and 2016 Proposed Changes
document).
Response: NMFS acknowledges that the LF cetacean predicted
weighting function and PTS onset thresholds in the 2016 Proposed
Changes document/Technical Guidance are more conservative than those
presented in the 2015 Draft Guidance. However, in our judgement, the
changes reflect the best available science and account for uncertainty
associated with this particular hearing group where data are limited.
In response to how the Technical Guidance could impact mitigation
ranges, see Response to Comment 11.
Mid- and High-Frequency Cetacean Hearing and Auditory Weighting
Functions
Comment 61: Multiple commenters indicated that the Guidance's
auditory weighting functions do not represent the hearing sensitivities
of all included species, indicating that bottlenose dolphins are not
appropriate surrogates for killer whales or sperm whales, which are
known to have regions of greatest hearing sensitivities at much lower
frequencies, and that harbor porpoises and finless porpoise may not
represent the auditory ability of Irrawaddy, Ganges River, Commerson's,
and Peale's dolphins.
Response: See Response to Comment 45. In the Guidance, a broader
range of species were considered in the development of the MF auditory
weighting function via the composite audiogram. Specifically, for MF
cetaceans, the composite audiograms are derived from data compiled from
eight species (bottlenose dolphins, beluga, false killer whale, Risso's
dolphin, striped dolphin, and tucuxi) and 22 individuals of these
species, of which only six individuals are bottlenose dolphins.
Further, two individuals of these are killer whales, which from these
available audiogram data indicate thresholds consistent with other MF
cetaceans (i.e., current audiograms do not indicate this species has
better low-frequency hearing than other MF cetaceans). Currently, there
are no direct measurements available on sperm whale hearing (only an
incomplete audiogram exists for a stranded sperm whale neonate from
Ridgway and Carder (2001)). NMFS considers sperm whale placement within
MF cetaceans appropriate based on Ketten (2000), which classified sperm
whales as having Type I cochlea, similar to other MF cetaceans and
considers the MF cetacean auditory weighting function representative of
all species within this hearing group based on the best available
science.
For HF cetaceans, composite audiograms are derived from more
limited data (i.e., four individuals from two species: harbor porpoise
and Amazon River dolphin; AEP data are only available for Yangtze
finless porpoise). Thus, it is unclear how these two species represent
others in this hearing group, since no other data are available (i.e.,
no data on hearing ability of Irrawaddy, Ganges River, Commerson's and
Peale's dolphins). The need for additional audiograms, particularly
from the HF cetacean hearing group was added as a Research
Recommendation (Appendix B) in the Technical Guidance.
Comment 62: One commenter noticed an error in the audiograms used
to construct the composite audiogram for HF cetacean in the July 2015
Draft Guidance. They indicated that the harbor porpoise audiogram by
Kastelein et al. (2002), was later revised due to a problem with the
analysis of the sound stimuli, with the correct audiogram found in
Kastelein et al. (2010). Thus, it is recommended that NMFS use the 2010
data, instead of the 2002 data.
Response: NMFS re-evaluated the data used to construct the
composite audiogram for HF cetaceans and confirmed the assertion made
by the commenter that the wrong data set was initially used. This error
has been corrected for in the final Technical Guidance.
Comment 63: Several commenters, including the Commission, were in
support of moving the white-beaked dolphin from MF cetaceans to HF
cetaceans.
However, numerous other commenters indicated that moving this
species to a new hearing group was not scientifically supported. The
Navy specifically recommended that this species remain in the MF
cetacean hearing group based upon the following scientific support: (1)
A hearing threshold comparison between white-beaked dolphin (Nachtigall
et al., 2008), bottlenose dolphin (Johnson 1967), and harbor porpoise
(Kastelein et al., 2002; Kastelein et al., 2010) indicating white-
beaked dolphin do not have significantly better high-frequency hearing
than the bottlenose dolphin (for figure depicting comparison see:
https://www.regulations.gov/#!documentDetail;D=NOAA-NMFS-2013-0177-
0152); (2) white-beaked dolphin echolocation are more similar to those
of bottlenose dolphins (i.e., resembling broadband, exponentially-
damped sinusoids containing only a few cycles; Au 1980; Rasmussen and
Miller 2002) in contrast to echolocation emissions for harbor porpoises
and other species placed into the HF cetacean hearing group (e.g.,
Cephalorhynchus sp., Lagenorhynchus australis) (i.e., more narrowband,
longer in duration, and contain mostly high-frequency energy; Tougaard
and Kyhn 2010); and (3) Ketten's (2000) categorization of the cochlea
of white-beaked dolphin and bottlenose dolphin as ``Type II,'' while
the harbor porpoise cochlea is categorized as ``Type I'' (i.e.,
reinforcing the idea that the white-beaked dolphin is acoustically
more-closely related to the bottlenose dolphin than to porpoises).
Response: Upon re-evaluation, NMFS concurs that based on currently
available data, it is more appropriate for the white-beaked dolphin to
remain in the MF cetacean hearing group. The scientific support to move
this species from MF to HF cetaceans is not to the level of that of two
other members of the genus Lagenorhynchus Peale's and hourglass
dolphins. (Note: In the Navy's justification above, Ketten (2000) did
not analyze white-beaked dolphin cochlea but instead Pacific and
Atlantic white-sided dolphins (also members of the genus
Lagenorhynchus)).
Comment 64: The Commission supported NMFS' decision to include the
newly published audiogram of a harbor porpoise (Kastelein et al., 2015)
in the March 2016 Proposed Changes document. However, other commenters
indicated that NMFS provided incomplete information on this dataset
making it impossible to conduct a meaningful comparison to the July
2015 Draft Guidance.
Response: NMFS disagrees that incomplete information was provided
in the March 2016 Proposed Changes document associated with the
addition of a newly published harbor porpoise audiogram (Kastelein et
al., 2015). The addition of this audiogram did not change the
fundamental methodology associated with the Guidance (i.e., Appendix
A), rather it only added a
[[Page 51710]]
newly available dataset, as will be the case as new data become
available in the future.
Pinniped Hearing and Auditory Weighting Functions
Comment 65: NMFS received a comment indicating that there are not
enough data to establish two separate weighting functions for
pinnipeds.
Response: NMFS disagrees. There are audiogram data available from
three species (eight individuals) of OW pinnipeds and four species
(eight individuals) of PW pinnipeds. Further, based on NMFS' review of
the literature, phocid species have consistently demonstrated an
extended frequency range of hearing compared to otariids, especially in
the higher frequency range. This is believed to be because phocid ears
are anatomically distinct from otariid ears in that phocids have
larger, more dense middle ear ossicles, inflated auditory bulla, and
larger portions of the inner ear (i.e., tympanic membrane, oval window,
and round window), which make them more adapted for underwater hearing.
If one examines the composite audiograms for these two pinniped groups,
distinct differences appear, supporting NMFS' decision to establish two
distinct pinniped hearing groups.
Comment 66: Numerous commenters questioned the justification for
the removal of some of the pinniped datasets based on non-
representative hearing in the March 2016 Proposed Changes document. The
commenters noted that masking is a common issue with obtaining
audiogram data for animals in captivity and indicated that NMFS must
provide a specific explanation for why these particular datasets
contain unique masking problems that are unlike the other datasets used
in the Guidance. An additional commenter requested NMFS provide the
exact procedures as to how and why it removed unrepresentative or
outlier data from its datasets and consider that one reason for
unrepresentative data is due to exposure to anthropogenic sound. Other
commenters, including the Commission, were in favor of removing these
datasets.
Response: Decisions to exclude data were based on comparison of the
individual published audiograms and ambient noise characteristics with
those for other individuals of the same or closely related species. The
most common reasons for excluding an individual's data were abnormal
audiograms featuring high-frequency hearing loss (typically seen in
older animals) or ``notches'' in the audiogram, or data collected in
the presence of relatively high ambient noise which resulted in
elevated thresholds. Excluding these data ensured that the composite
audiograms were not artificially elevated, which could result in
unrealistically high impact thresholds. NMFS disagrees that previous
exposure to anthropogenic sources is the basis for deeming the datasets
unrepresentative, since currently available audiograms are derived from
captive individuals (i.e., there is no indication that anthropogenic
sound in captivity is directly impacting auditory thresholds, other
than via possible masking).
Comment 67: NMFS received several comments indicating that the
proposed changes to the PW pinniped ``a'' parameter, which defines the
slope of the low-frequency portion of the weighting function, were
arbitrary and unsupported. Additionally, a commenter noted an
inconsistency in this parameter (i.e., ``a'' parameter value provided
did not seem to match what was depicted on the PW pinniped weighting
function). Finally, the commenters criticized that the March 2016
Proposed Changes document illustrated (Figure PC5) that the PW exposure
functions was only based on one data point.
Response: The PW pinniped ``a'' parameter is directly derived from
PW pinniped behavioral audiograms (8 individuals of 4 species).
Additionally, the 2016 Proposed Changes document removed
unrepresentative datasets, which resulted in a steeper slope (``a'' =
1.0) compared to the 2015 Draft Guidance (``a'' = 0.8).
Upon re-evaluation, NMFS agrees that there was a slight discrepancy
with the ``a'' parameter depicted in the weighting function provided
for PW pinnipeds in the March 2016 Proposed Changes document. This has
been remedied with the correct value portrayed for this hearing group's
auditory weighting function.
Finally, the March 2016 Proposed Changes document (Figure PC5)
illustrates available TTS data for all hearing groups. NMFS agrees that
data are limited particularly for PW pinnipeds (i.e., two TTS onset
data points). Nevertheless, it should be noted that the exposure/
weighting functions are not merely based on TTS onset data but also
incorporate available audiogram data each for hearing group.
Comment 68: A commenter questioned if there was an error in
Appendix A, specifically with the best-fit parameters associated with
the derivation of the composite audiogram (original and normalized
data) for PW pinnipeds in Table A4. These tables indicate an unusually
high ``F1'' value (excess of 300 kHz) and an anomalous
``T0'' value of negative decibels.
Response: Upon re-evaluation, NMFS determined that the best-fit
parameters for PW are not anomalous or in error. These parameters
mentioned by the commenter are merely fitting parameters for equation 9
in Appendix A and do not directly correspond to a particular feature of
the audiogram (i.e., F1 does not represent the frequency at which the
audiogram reaches a specific value). The value for F1
influences the frequency at which thresholds begin to plateau near the
best sensitivity. Very large values for F1 (and the
accompanying small value for T0) simply reflect little or no
plateau in the thresholds in the region of best sensitivity. In many
respects, the specific numeric values applied to Equation 9 in Appendix
A of Technical Guidance are not key; what matters are the resulting
shapes of the composite audiograms and how well they match the
underlying threshold data.
Comment 69: One commenter suggested that the two species of PW
pinnipeds (i.e., harbor seal and northern elephant seal) mentioned in
the Guidance are commonly found in close proximity to human population
centers and are not good proxies for Arctic and Antarctic seals.
Response: The Technical Guidance relies on more data than from
harbor seal and northern elephant seal. Additionally data from two
Arctic species (spotted seal from Sills et al. (2014) and ringed seal
from Sills et al. (2015)) were used to derive composite audiogram for
PW pinnipeds. Thus, data from four different PW pinniped species were
used to derive composite audiograms for this hearing group. NMFS
believes currently available data are representative of all PW
pinnipeds, including polar species.
Application of Auditory Weighting Functions
Comment 70: One commenter requested that NMFS provide additional
clarification as how the auditory weighting functions were applied to
the data used to develop acoustic thresholds (e.g., were the auditory
weighting functions applied to the entire raw data before calculating
the SELcum) and examples of software that could be used to
apply these weighting functions.
Response: Marine mammal auditory weighting were directly
incorporated in the derivation of thresholds associated with non-
impulsive sounds and then were directly applied in the derivation of
impulsive thresholds, since only limited data are available (Details in
[[Page 51711]]
Appendix A). Section 2.2.4 of the Technical Guidance (Main Document)
provides more detail on how to implement/apply these weighting
functions. For a source consisting of a single tone, the application of
auditory weighting functions is a straight forward process (i.e., only
single frequency to consider). For broadband sounds, the application is
more complicated (i.e., must consider multiple frequencies), which is
why NMFS included alternative weighting factor adjustments for when
frequency weighting functions cannot be fully incorporated (Appendix
D).
Comment 71: One commenter noted that the LF cetacean acoustic
thresholds do not appear to be adjusted based on the LF cetacean
auditory weighting functions and asked whether the threshold for LF
cetaceans exposed to an airgun/watergun with most of its energy in
their primary hearing band as measured in the experiment should be
adjusted.
Response: Marine mammal TTS data for impulsive sources exist only
for two hearing groups (i.e., MF and HF cetaceans). For other groups,
alternative methodology was developed using MF and HF cetaceans as
surrogate data and assuming the relationship between impulsive and non-
impulsive thresholds is conserved among hearing groups (i.e.,
methodology resulted in a TTS onset threshold for impulsive sources
that is 11 dB lower than the TTS threshold onset for non-impulsive
sources). NMFS disagrees that any adjustment needs to be made to the LF
cetacean acoustic thresholds. Weighting functions are also implemented
in exposure modeling, which will take into account whether or not a
sound falls within a hearing group's most susceptible frequency range.
Comment 72: A few commenters indicated that Tougaard et al. (2013)
note that auditory weighing functions cannot themselves be
``conservative'' if applied in establishing and then implementing
acoustic thresholds. To achieve a conservative approach, the commenters
suggested the application of a more tailored function at the acoustic
threshold determination stage in combination with a wider and more
energy-inclusive function at the implementation stage. The commenters
suggested that NMFS use a function normalized to a lower level (e.g., -
3 dB) for establishing acoustic thresholds, while using functions
normalized to a higher level (e.g., 0 dB) for estimating the number of
``takes'' when implementing these thresholds. The commenters provided
the example that JASCO Applied Sciences typically incorporates a 3-dB
precautionary adjustment in their propagation modeling to account for
uncertainty.
Response: The Technical Guidance explains that auditory weighting
functions are considered within both the data evaluation and
implementation processes, as pointed out by Tougaard et al. (2013) (now
published Tougaard et al., 2015). NMFS acknowledges that adjustments
during the data evaluation process that result in a lower threshold
could potentially translate to smaller isopleths, if a source has
energy in frequencies outside a hearing groups most susceptible hearing
range (i.e., weighting functions are essentially filters; their
application results either in the same size or in smaller isopleths or
the same or lower thresholds). Tougaard et al. (2015) provide some
important factors for consideration when applying weighting functions
in both the context of data evaluation and implementation. However,
NMFS does not find it appropriate to normalize the Technical Guidance's
acoustic thresholds, as suggested by the commenters, as there are no
data to support doing so. Further, several conservative assumptions
were applied to the derivation of acoustic thresholds to account for
uncertainty and limited data (see Response to Comment 77). Finally,
NMFS' application of auditory weighting functions is consistent with
what has been done for humans (i.e., A-weighted thresholds used in
conjunction with A-weighting during implementation).
As for the 3-dB adjustment JASCO Applied Sciences makes to the
results of their propagation models, this adjustment is based on their
best fit analysis, where 90 percent of all their measured values fall
within 3 dB of the mean level (e.g., see any recent SSV reports from
JASCO Applied Sciences, like Beland et al. (2013), for more details).
NMFS used this same premise to re-examine the TTS onset thresholds for
non-impulsive sources for data collected via both the preferred
behavioral technique as well as AEP methodology, the next tier in our
data hierarchy (the same analysis could not be done for impulsive
sources, where data are limited to two studies). It was found that for
all hearing groups, except PW pinnipeds, the TTS onset thresholds
encompassed more than 90 percent of available TTS data (MF cetaceans,
only two points below the onset threshold, with maximum point only 2 dB
below), and in some situations 100 percent of TTS data (i.e., OW and HF
cetaceans; although both these groups are data limited). For PW, which
are also data limited, only one of the five available data points was
below the TTS onset threshold (i.e., 1 dB below the threshold). Thus,
NMFS believes any further adjustments to the thresholds are unnecessary
and that they provide realistic predictions, based on currently
available data, of noise-induced hearing loss in marine mammals.
Temporary Threshold Shifts
Comment 73: One commenter cautioned that a 6 dB threshold shift may
be appropriate for testing TTS but should not be confused with the
level that is biologically important (e.g., 6 dB corresponds to a
roughly 8-fold decrease in the volume in which biologically significant
sounds can be detected through passive listening).
Response: The Technical Guidance considers a threshold shift of 6
dB the minimum threshold shift clearly larger than any day-to-day or
session-to-session variation in a subject's normal hearing ability and
is typically the minimum amount of threshold shift that can be
differentiated in most experimental conditions (Schlundt et al., 2000;
Finneran et al., 2000; Finneran et al., 2002). Similarly, for humans,
NIOSH (1998) regards the range of audiometric testing variability to be
approximately 5 dB. Because the Technical Guidance does not address the
biological significance of passive listening, NMFS has set the onset of
TTS at the lowest level that exceeds recorded variation and could be
considered biologically significant.
Comment 74: One commenter noted that the Guidance appeared to use
temporary threshold shift (TTS) when it may mean threshold shift (TS)
and suggested that NMFS use terms consistently and clearly.
Another commenter requested the Guidance make clear that a
threshold shift is a symptom of noise exposure rather than an impact
(i.e., a manifestation of an anatomical alteration that deters or
eliminates auditory responses). The commenter emphasized that
impairments arise from other acoustic features associated with what the
ear receives (i.e., not necessarily characteristics associated with the
source), and there are multiple components to any received sound (e.g.,
received level, timing, intensity, sensitivity, time course, recovery
period), all of which may act singly or in concert to impact an ear at
any frequency and for any species, whether in air or water. As such,
the commenter suggested the Guidance include a brief statement
indicating the choice of using a threshold shift to assess the effects
of noise on hearing is one driven by practicality (i.e., Guidance does
not address all critical features associated
[[Page 51712]]
with impacts from sound, but there is an awareness and expectation that
other features require investigation and that these may ultimately
alter the thresholds according to their interplay and relative
potential for harm).
Response: NMFS has revised the Technical Guidance to clearly
distinguish between a threshold shift (temporary or permanent) as a
term which indicates the increase in threshold of audibility (i.e., 6
dB for onset of TTS and 40 dB for onset of PTS) versus the exposure
level (i.e., acoustic threshold) associated with that shift.
NMFS agrees that a threshold shift is a ``symptom'' rather than an
``impact.'' However, in the context of the Technical Guidance and in
terms of how the acoustic thresholds will be used, the term/concept of
``impact'' is one that readers of the document will be more familiar
with. NMFS also agrees that features of the signal at the receiver are
most important, but are often most difficult to determine. The
Technical Guidance includes more information explaining when choices
are based on considerations of practicality because of complexity and
makes various research recommendations to address these issues
(Appendix B).
Comment 75: Several commenters requested clarification on the
application of TTS onset acoustic thresholds presented in the Guidance
under NMFS' relevant statutes, including the Commission, which
recommended all applicants be required to use the Guidance's TTS onset
thresholds. The Commission requested further clarification on how the
Guidance's TTS thresholds are to be implemented in conjunction with
NMFS' generic RMS SPL 120/160 dB behavioral thresholds.
Response: The Technical Guidance sets forth the levels at which TTS
and PTS onset are likely to occur. In this Federal Register Notice
(Regulatory Context), we describe our current agency practice for
assessing take and refer readers to that section (this information
previously appeared in the Draft Guidance Regulatory Context section).
In short, PTS onset is treated as Level A harassment under the MMPA and
harm under the ESA (as well as injury under NMSA as administered by
NOS' National Marine Sanctuary Program), and NMFS recommends using the
Technical Guidance to estimate take from PTS exposures in regulatory
compliance documents.
Regarding TTS, with the exception of underwater explosives (see
Regulatory Context), NMFS does not currently recommend calculations of
TTS exposures separate from assessments of Level B harassment or ESA
harassment using the prior existing thresholds for enumerating
behavioral takes. NMFS is in the process of evaluating behavioral
effects thresholds and intends to develop related guidance for use in
its regulatory processes. Because the effects in consideration when TTS
is incurred are behavioral and temporary in nature, much like
behavioral responses, we intend to address those effects in the context
of regulatory compliance at that time.
Comment 76: Multiple commenters indicated an inconsistency in the
Guidance in the characterization of TTS among NOAA's various statutes
(i.e., NMFS collectively does not consider TTS an auditory injury, but
TTS is considered injury under the broad definition of the NMSA) and
suggested NOAA implement a consistent regulatory interpretation of the
term injure when addressing acoustic exposures on marine mammals.
Response: The Guidance is a technical document that compiles,
interprets, and synthesizes the scientific literature, to produce
updated, scientifically-based, impact thresholds for assessing the
effects of noise on hearing. Although these changes may necessitate new
methodologies for calculating impacts, the application of the
thresholds under applicable statutes remains consistent with past and
current NMFS practice. See Regulatory Context section in this Federal
Register Notice. That information was moved out of the main body of the
Guidance to emphasize the distinction between the scientific exercise
of developing updated thresholds, which is science-based, and the
application of thresholds in the regulatory arena, which is also
informed by policy and legal considerations.
Comment 77: Multiple commenters recommended that NMFS consider
threshold shifts requiring extended recovery periods (e.g., in excess
of 24 hours), as well as nerve and other related damage, to be included
in the definition of injury. The commenters expressed concern that NMFS
did not consider the results of Kujawa and Liberman (2009) and Lin et
al. (2011), and suggested the Guidance state that the PTS acoustic
thresholds will be conservatively revised in the future to reflect any
new evidence showing correlations of injurious effects of TTS below
these new acoustic thresholds.
Response: NMFS recognizes this is an area where additional study is
needed. NMFS has included several conservative assumptions in its
protocol for examining marine mammal hearing loss data (e.g., using a 6
dB threshold shift to represent TTS onset, not directly accounting for
exposure levels that did not result in threshold shifts, assuming there
is no recovery with the 24-h baseline accumulation period or between
intermittent exposures, etc.).
The Technical Guidance includes information from Kujawa and
Liberman (2009) and Lin et al. (2011) as a way to illustrate the
complexity associated with noise-induced hearing loss and as an area
where more research is needed (Appendix B). NMFS finds that these
studies would be informative for use as qualitative considerations
within the comprehensive effects analysis. NMFS acknowledges the
complexity of sound exposure on the nervous system, and will re-examine
this issue as more data become available.
Comment 78: One commenter indicated that in Germany, TTS is
considered the onset of injury. The commenter suggested that since many
countries may adopt this Guidance rather than developing their own,
NMFS make clear that choosing PTS as onset for injury is based on U.S.
legal considerations.
Response: This Federal Register Notice contains a section
explaining the current U.S. regulatory context for using the acoustic
thresholds contained in the Technical Guidance.
Comment 79: Several commenters indicated that chronic, repeated
exposures to levels capable of inducing TTS can lead to PTS and
recommended that NMFS consider cumulative effects of all anthropogenic
sound sources in terms of long-term exposure in the development of the
Guidance's acoustic thresholds, as well as within the context of NEPA.
Specifically, it was suggested that, apart from the accumulation time
applied to any single activity (i.e., acoustic thresholds), NMFS add
repeated, intermittent exposure to multiple acoustic activities to its
table of ``qualitative factors for consideration.''
Response: NMFS acknowledges that cumulative effects and long-term
exposure of noise are important considerations in understanding the
impacts of sound on marine mammals and that repeated exposures
initially resulting in TTS have the potential to result in PTS.
However, they are beyond the scope of this document, in terms of
developing quantitative acoustic thresholds and are being considered by
other mechanisms within or supported by NOAA (e.g., NOAA Ocean Noise
Strategy and CetSound Projects; National Research Council's Ocean
Studies Board's Cumulative Effects of Human Activities on Marine Mammal
Populations Study). The Technical Guidance focuses on acute exposures
to
[[Page 51713]]
noise and threshold shifts associated with these types of exposures.
Additionally, the TTS data currently available for marine mammals only
support deriving thresholds for these types of short-term exposures,
rather than long-term/chronic exposure. Having data to address more
realistic exposure scenarios, including repeated exposures, have been
identified within our Research Recommendation Appendix (Appendix B).
NMFS has added cumulative exposures to its recommended qualitative
factors to consider within a comprehensive effects analysis. The
discussion of qualitative factors has been moved from the main Guidance
document to Appendix B (See Response to Comment 130).
Comment 80: One commenter recommended that since seismic activities
do not cause PTS and TTS ``during realistic field conditions,'' there
is no need to apply the new PTS and TTS acoustic thresholds levels in
the Guidance to these activities.
Response: NMFS notes that the only marine mammal TTS data available
are from laboratory studies, and that there are no TTS data available
for any sound source in more realistic field conditions. Nevertheless,
marine mammal laboratory studies offer vital information on exposure
situations that can result in noise-induced threshold shifts, and NMFS
used this information to establish acoustic thresholds for free-ranging
animals exposed to anthropogenic sound sources in their natural
environment. NMFS is not aware of any evidence to indicate that seismic
sound sources should be treated differently than any other
anthropogenic sound source.
Uncertainty and Statistical Analyses Associated With Temporary
Threshold Shift Data
Comment 81: Several commenters suggested that where a potential for
uncertainty exists NMFS should proceed cautiously and consider
adjustments to thresholds that are most protective of the animals. One
commenter specifically urged NMFS to consider the precautionary
principle within the Guidance and NOAA's need to comply with its own
statutes.
Response: The Technical Guidance identifies areas of uncertainty
and data limitations (Appendix A) and has made several conservative
assumptions to account for this (e.g., defining TTS onset as the level
just above where individual variability in hearing occurs, not
accounting for exposures where TTS onset did not occur, etc.). See
Response to Comment 49 for more details on the issue of uncertainty.
Additionally, a Research Recommendations section has been added to
identify data gaps (Appendix B). As more data become available, NMFS
can explore more sophisticated means of analysis.
As previously indicated, the acoustic thresholds do not represent
the entirety of an effects analysis, but rather serve as one tool to
help evaluate the effects of a proposed action and make findings
required by NOAA's various statutes. Further, other measures can be
employed to account for uncertainty beyond considerations within the
Technical Guidance (e.g., mitigation/monitoring requirements).
Comment 82: Multiple commenters recommended that the procedures for
establishing acoustic thresholds be revised to use the lowest available
value or correction factor to account for the full representation of
the distribution of TTS/PTS onset in a population rather than using the
median value if five or more data points are available. Specifically,
commenters expressed concern that NMFS is producing a threshold closer
to the population mean (i.e., the point at which the first ``take'' is
estimated to occur is roughly 50 percent of any given population will
have already experienced a threshold shift) by relying on the median
value. These commenters suggested that NMFS investigate statistical
methods that deal with probabilities and distributions (e.g., Bayesian
statistics), which particularly account for individual variability and
uncertainty over the mean of threshold shift onset. These commenters
further indicated that these statistical methods or a simple less
precise alternative where the lowest reported TTS onset value was
always selected (instead of the median) would likely provide a more
appropriate estimation of TTS/PTS onset for a given proportion of the
population.
Contrary to the comments above, another commenter cautioned against
relying on the lowest onset with limited data because these data could
be outliers and result in overly conservative acoustic thresholds. The
commenter further indicated that overly conservative thresholds could
result in unrealistic exposure estimates and suggested NMFS' protocol
be modified to examine the distribution of the data and make a reasoned
decision about whether the lowest threshold might be an outlier and
whether (and how) it should be included in the determination of a
threshold.
Response: NMFS incorporated several conservative assumptions into
the derivation of the acoustic thresholds to account for uncertainty
and variability (see Response to Comment 77). The comment's reference
to use of a median value if five or more data points are available
refers to proposed methodology from the 2013 Draft Guidance. The 2015
Draft Guidance contained updated methodology for deriving TTS/PTS onset
acoustic thresholds which better account for available marine mammal
data (see Response to Comment 72).
NMFS used the best available science to develop the Technical
Guidance. As more data are collected, NMFS will be better able to
identify outliers (e.g., one individual has an unusually high or low
threshold or testing procedures led to flawed results) and consider
necessary adjustments (i.e., removal of an outlier datum).
Comment 83: Multiple commenters expressed concern associated with
the Guidance's low acoustic thresholds for the HF cetacean hearing
group. Specifically, the commenters indicated that for impulsive sound,
the thresholds are based on data from a single study involving a single
animal (harbor porpoise) (Lucke et al., 2009), and for non-impulsive
sound, the threshold is based on a single study involving only two
animals (Popov et al., 2011). The commenters remarked that both studies
have potential biases and uncertainty and urged NMFS to allow for
flexibility in the implementation of acoustic thresholds in future
regulatory processes.
Response: NMFS acknowledges that, for most hearing groups, data are
available only from a limited number of species and a limited number of
individuals within that species. The need for more data from all
species is highlighted in the newly added Research Recommendation
section of the Technical Guidance (Appendix B).
In addition, new data have become available since the NMFS received
this comment during the first public comment period. As indicated in
the Technical Guidance, the acoustic threshold (SELcum
metric) for HF cetaceans exposed to non-impulsive sound was derived
using data from three studies (i.e., Kastelein et al., 2012, Kastelein
et al., 2014a, and Kastelein et al., 2014b, not Popov et al., 2011a,
which did not derive TTS onset and relied on AEP methodology). These
new studies support results from Lucke et al. 2009 indicating that
harbor porpoises have a lower TTS onset than other cetaceans (i.e.,
reason for separating MF and HF cetaceans into separate hearing
groups).
NMFS recognizes that acoustic thresholds for HF cetaceans, which
are based exclusively from harbor porpoise
[[Page 51714]]
data, are much lower than other hearing groups, and therefore some
additional considerations may be warranted on a case-by-case basis.
However, it also should be noted that auditory weighting functions
should be considered when evaluating impacts of sound on HF cetaceans,
which are most susceptible to injury from higher frequency sounds
(e.g., 25 to 60 kHz).
Comment 84: Multiple commenters recommended a precautionary
approach (i.e., more conservative thresholds) when applying the
Guidance to activities and species in the Arctic.
Response: NMFS recognizes that marine mammals in the Arctic are
experiencing increasing pressures from human activities (e.g., climate
change, increased commercial activities). However, NMFS does not find
that there are data to indicate greater susceptibility of Arctic
species to noise-induced hearing loss compared to non-Arctic species.
Data from two Arctic species (spotted seal from Sills et al., 2014 and
ringed seal from Sills et al., 2015) were used to derive composite
audiograms for PW pinnipeds. Additionally, measured underwater hearing
of two captive spotted seals (Sills et al., 2014) and two captive
ringed seals (Sills et al., 2015) found these species' hearing
abilities are comparable to harbor seals. Thus, harbor seals (i.e.,
only phocid with TTS data are available) are believed to be an
appropriate surrogate for ice seal species.
Further, audiogram data from belugas (n=9; more individuals of this
species than any other) were specifically used to derive composite
audiograms for MF cetaceans. In addition, recent data from Castellote
et al. (2014), from free-ranging belugas in Alaska, indicate of the
seven individuals tested (3 females/4 males; 1 subadult/6 adults), all
had hearing abilities ``similar to those of belugas measured in
zoological settings.'' Thus, from this study, it appears that for
baseline hearing measurements, captive individuals are an appropriate
surrogate for free-ranging animals. The Technical Guidance also
incorporates TTS data (i.e., TTS onset and TTS growth rate) are
available from four individual belugas (e.g., Schlundt et al., 2000;
Popov et al., 2014)
Thus, data from Arctic species are directly incorporated into
numerous aspects of the Technical Guidance's methodology. These data
indicate additional conservative adjustments in determining thresholds
unnecessary. Precautionary adjustments may be made elsewhere (e.g.,
applied in a specific regulatory context of fully evaluating effects,
authorizing, and developing mitigation for an action).
Cetacean Temporary Threshold Shift Data
Comment 85: There was concerned expressed that the low TTS onset
thresholds for HF cetaceans exposed to impulsive sources results from a
AEP study, opposed to one using behavioral methods, and that this
violates the methodology of only using behavioral data stipulated in
Appendix A of the Guidance. Contrary to this comment, multiple
commenters advocated for the inclusion of TTS data derived using AEPs
into the Guidance's methodology.
Response: As mentioned in earlier, NMFS established an informal
data hierarchy in consideration of the development of the Technical
Guidance's composite audiograms and acoustic thresholds (see Response
to Comment 43), with the best-representative data being used over other
sources. In the case of deriving TTS acoustic thresholds for HF
cetaceans, only one dataset is currently available (Lucke et al.,
2009), which relies on AEP measurements. Appendix A specifically
addresses this issue: ``Note that the data from Lucke et al. (2009) are
based on AEP measurements and may thus under-estimate TTS onset;
however, they are used here because of the very limited nature of the
impulse TTS data for marine mammals and the likelihood that the high-
frequency cetaceans are more susceptible than the mid-frequency
cetaceans (i.e., use of the mid-frequency cetacean value is not
appropriate).''
There have been limited comparisons of TTS data collected via
behavioral versus AEP methods for any marine mammals, especially marine
mammals. There is only one available marine mammal study (Finneran et
al., 2007) that found threshold shifts of 40 to 45 dB associated with
AEP methods and 19 to 33 dB thresholds shifts measured via behavioral
methods. These two methodologies do not provide the same results (i.e.,
AEP methods consistently produce higher thresholds compared to
behavioral techniques), and there is currently no accurate means
available to ``correct'' AEP data so that it can be more comparable to
those obtained via behavioral techniques.
Comment 86: One commenter requested the Guidance provide additional
clarification on the TTS PK acoustic threshold of 224 dB for MF
cetaceans and suggested a 226 dB value be used instead, as is cited in
Finneran et al. (2002).
Response: NMFS notes the Guidance's MF cetacean TTS onset PK
threshold is based on the pressure levels originally expressed as
pounds per square inch (psi) presented in Finneran et al. (2002). This
value was then converted from psi to peak pressure levels (i.e., 23 psi
is equivalent to PK 224 dB). The PK 226 dB, referred to by the
commenter, was a peak-to-peak pressure level and not a peak pressure
level (i.e., different metric), which was why it was not directly
applied to the Technical Guidance.
Comment 87: The Commission recommended that instead of using the MF
cetaceans' PK thresholds as surrogates for other hearing groups where
no data are available that NMFS consider dynamic range (i.e.,
difference between threshold at frequency of best hearing sensitivity
and peak pressure threshold) for deriving peak pressure thresholds, as
has been used for humans (e.g., 140 dB from Occupational Safety and
Health Administration, OSHA). The Commission specifically suggested
NMFS apply the measured dynamic range from HF cetaceans to the derive
thresholds for LF cetaceans, PW pinnipeds, and OW pinnipeds.
Contrary to the Commission's recommendation, several commenters
criticized NMFS' use of dynamic range to predict PK thresholds.
Specifically, commenters questioned NMFS use of onset TTS to define
dynamic range, since the onset of TTS is not equivalent to the
threshold of pain and therefore overly conservative (i.e., different
between TTS onset and PTS is approximately 40 dB). Additionally, these
commenters indicated that dynamic range data are available for both
pinniped hearing groups (Kastak et al., 2005) and should be used
instead of surrogate data from MF and HF cetaceans.
Additionally, one group of commenters requested NMFS provide more
information on why the median dynamic range for MF and HF cetaceans was
used as a surrogate for LF cetaceans.
Response: NMFS evaluated the Commission's recommendation of an
alternative methodology for deriving PK thresholds using dynamic range
and determined that it is a more valid approach to approximating PK
thresholds for hearing groups where no data exist. However, NMFS
determined that using the dynamic range for HF cetaceans for other
hearing groups was not appropriate and instead used the median of the
dynamic range from both MF and HF cetaceans to derive PK thresholds for
PW and OW pinnipeds and LF cetaceans.
As for comments criticizing the Technical Guidance's methodology
for establishing PK thresholds based on dynamic range, NMFS notes that
[[Page 51715]]
``dynamic range'' can have many connotations. In the Technical
Guidance, we relate hearing threshold and TTS onset levels, and
therefore define dynamic range based on hearing threshold and TTS
onset. Furthermore, NMFS does consider a 40 dB threshold shift to
represent the PTS onset and uses this value to approximate PTS onset
thresholds from available TTS onset data (i.e., TTS growth rate data).
NMFS re-evaluated data within Kastak et al. (2005) to consider for
establishing PK pressure thresholds for pinnipeds, rather than using
surrogate MF and HF cetacean data. Within this publication, NMFS could
not find any information on dynamic range for pinnipeds or any other
publication that provides impulsive data for pinnipeds. Therefore,
dynamic range cannot be directly calculated for pinnipeds and surrogate
data had to be used.
As for the request for more information on why a surrogate dynamic
range from MF and HF cetacean data was used for LF cetaceans, NMFS
relied on the methodology used in other situations to derive surrogate
values for species groups where data do not exist (i.e., use data from
other hearing groups, assuming groups where data are not available fall
within the bounds of existing marine mammal data). Until data become
available for these hearing groups, NMFS believes this method is an
appropriate means of deriving surrogate values.
Comment 88: Multiple commenters expressed concern that the Guidance
excludes studies in which TTS was not induced, and that, as a result,
the acoustic thresholds could represent exposure scenarios that will
not necessarily result in TTS under all conditions. The commenters
suggested that Guidance's thresholds should only be used to estimate
the number of animals that could potentially experience TTS (i.e.,
acoustic exposure levels describe potential and not actual TTS onset
for all exposure scenarios) and that exposures not inducing TTS be
directly included and used to develop the Guidance's acoustic
thresholds. The commenters stressed that this distinction is important
because the Draft Guidance defines TTS, not ``potential TTS,'' as Level
B harassment and that how Level B harassment is estimated has important
relevance to the ``small numbers'' and ``negligible impact''
determinations that must be made in support of MMPA incidental take
authorizations.
Response: The Technical Guidance itself does not rely upon or
address regulatory practice or interpretations. The section of the
Draft Guidance that discussed application of thresholds in the
regulatory context for informational purposes has been more
appropriately placed in this Federal Register Notice (see Regulatory
Context). However, to account for uncertainty and limited data, the
Technical Guidance used a conservative protocol to estimate the onset
of TTS (see Response to Comment 77). NMFS agrees that exposure
scenarios where TTS could not be induced are not directly accounted for
in the development of the quantitative acoustic thresholds.
Nevertheless, in some situations, studies where TTS could not be
induced are used to evaluate (cross-check) the Guidance thresholds
(e.g., HF cetacean pile driving data; MF cetacean seismic airgun data,
MF cetacean explosion simulator data). As more data become available,
NMFS may explore alternative means of deriving acoustic thresholds
(e.g., protocol that directly accounts for scenarios when threshold
shifts do and do not occur).
Comment 89: The Commission indicated that TTS data have not been
collected for either HF or MF cetaceans below 1 kHz. Further, they
recommend that measurements of TTS frequencies lower than 1 kHz and TTS
measurements associated with exposure to multiple pulses/hammers
strikes be added the Guidance's Research Recommendations (Appendix B).
Response: Although limited, TTS data have been collected at
frequencies below 1 kHz for HF and MF cetaceans. Finneran et al. (2015)
exposed bottlenose dolphins (MF cetaceans) to multiple impulses from
seismic airguns measured TTS at a range of frequencies (0.5 to 64 kHz)
for three individuals (see Figure 6 in Finneran et al., 2015b).
Additionally, Kastelein et al. (2015) exposed a harbor porpoise (HF
cetacean) to playbacks of offshore pile driving and measured TTS at a
range of frequencies from 0.5 to 125 kHz. Finally, Kastelein et al.
(2014) exposed harbor porpoise (HF cetaceans) to 1 to 2 kHz sonar
sweeps and measured TTS at 1.5 kHz. NMFS agrees with the Commission's
recommendations for additional research and has added them to Appendix
B of the Guidance (i.e., Sound Exposure to More Realistic Scenarios).
Pinniped Temporary Threshold Shift Data
Comment 90: One commenter remarked that pinnipeds are likely to be
less sensitive to noise compared to cetaceans and expressed concern
that the Guidance's extrapolations using cetaceans as surrogates for
pinnipeds may be flawed. Given the current lack of information, the
commenter suggested the highest threshold values from any of the
cetacean hearing groups (and not any higher) be used to establish the
underwater acoustic thresholds for pinnipeds.
Response: In establishing the pinniped thresholds, NMFS used the
best available data (i.e., non-impulsive TTS thresholds are based on
measurements collected from three individual harbor seals and a single
California sea lion) and acknowledges that in some situations where no
pinniped data were available, cetacean data were used as surrogate data
to derive acoustic thresholds for pinnipeds. As an example, for PK
thresholds, data from MF cetaceans and HF cetaceans were used to
determine an appropriate dynamic range for pinnipeds, but this
surrogate dynamic range was then combined with direct data on hearing
thresholds from pinnipeds to derive these thresholds (i.e., combination
of pinniped and other marine mammal data). As more direct pinniped data
become available, NMFS will re-evaluate these acoustic thresholds. This
has specifically been identified as a data gap within the Research
Recommendation Appendix (Appendix B) of the Technical Guidance.
Comment 91: A commenter expressed concern that the thresholds for
OW pinnipeds were much higher than other hearing groups, especially
that the SELcum thresholds are not much lower than the PK
threshold. It was indicated that these values appear anomalous and
should be verified.
Response: NMFS re-evaluated the data used to derive the OW pinniped
acoustic thresholds. There are only limited data available for this
hearing group, with TTS onset thresholds for non-impulsive sources
coming from a single California sea lion. This threshold is 18 dB
higher than that for PW pinnipeds and at least 20+ dB higher than the
thresholds for the cetacean hearing group. Additionally, with the
updated methodology to estimate PK thresholds using dynamic range (2016
Proposed Changes document), the OW pinniped PK thresholds have
increased by 2 dB compared to the thresholds in the 2015 Draft
Guidance. Due to lack of data for OW pinnipeds, surrogate datasets or
methodologies to approximate TTS onset for impulsive sounds and PTS
onset levels had to be used. These approximations build upon the one
data set available for OW pinnipeds. Thus, all the resulting thresholds
are higher than those of other hearing groups. This has been
highlighted within the Technical
[[Page 51716]]
Guidance's Appendix B: Research Recommendations.
Alternative Acoustic Thresholds (Optional Means To Incorporate
Weighting Functions)
Comment 92: One commenter suggested that there is no justification
or explanation for the process for alternative acoustic thresholds
within the 2015 Draft Guidance and that attempts to compare the results
of using these alternative thresholds seem to produce conservative
(i.e., higher) levels of exposure when compared to the thresholds the
encompass the full auditory weighting function.
Response: Based on public comment, NMFS re-evaluated its proposed
alternative acoustic thresholds and replaced this methodology with
optional weighting factor adjustments (WFAs) that more realistically
incorporate marine mammal auditory weighting functions for all hearing
groups (not just HF and MF cetaceans) and allow for all action
proponents to use the same acoustic thresholds.
NMFS has included additional explanation in the final Technical
Guidance's Appendix D. For situations where the full auditory weighting
functions cannot be incorporated, updated weighting factor adjustments
are provided, which are based on broader, simpler consideration of
weighting functions (i.e., relies on using a single frequency that best
represents where a particular sound has energy). Incorporating optional
WFAs should result in similar if not identical isopleths for narrowband
sources and slightly more conservative isopleths (albeit more realistic
than the previous alternative threshold methodology) for broadband
sources compared to those action proponents that can fully incorporate
the Technical Guidance's auditory weighting functions.
Comment 93: The Commission questioned the utility of two sets of
thresholds in the Guidance (i.e., weighted and unweighted), noting that
if an action proponent can calculate or determine the isopleths
(distances) to the relevant thresholds (weighted or unweighted) then
that same action proponent should be able to apply the auditory
weighting functions. The Commission suggested that NMFS require action
proponents to use the best available science, including auditory
weighting functions and relevant weighted thresholds, rather than give
action proponents the choice of using unweighted thresholds.
Response: NMFS notes that the updated optional WFAs, which replace
the Draft Guidance alternative thresholds, are provided for action
proponents unable to fully incorporate auditory weighting functions.
This is because, especially for broadband sources (which most
anthropogenic sources are), this incorporation is not a simple
calculation (i.e., it depends upon the spectrum of the source). NMFS
regards the practicality of applying more complex, updated thresholds
an important consideration. This is why NMFS has provided the simpler
optional WFA approach, which allows action proponents to apply
weighting in a simpler manner (i.e., most appropriate single
frequency). The use of WFAs results in all action proponents using on
the same thresholds.
Comment 94: Several commenters suggested that the Guidance provide
clear direction on which thresholds should be used and under what
specific circumstances. Further, multiple commenters noted that the
Guidance's alternative thresholds (updated WFAs in final Technical
Guidance) represent a simple and conservative way to present the
thresholds and recommended that they be applied to all action
proponents. Doing so, the commenters suggested, would simplify
implementation for all authorization action proponents, as well as
those processing and reviewing the applications, including the
associated public comment by increasing transparency and reducing
application processing time.
Response: As indicated in the Response to the previous comment,
alternative thresholds have been removed from the final Technical
Guidance, such that all action proponents are using identical
thresholds, regardless of their ability to incorporated marine mammal
weighting functions. NMFS appreciates the need for clarity and has
included more information in the final Technical Guidance's Appendix D
regarding when optional WFAs should be used. Specifically, text has
been added to indicate that NMFS recognizes that the implementation of
marine mammal auditory weighting functions represents a new and
complicating factor for consideration, which may extend beyond the
capabilities of some action proponents and that NMFS has developed
optional WFAs for those who cannot fully apply weighting functions
associated with the SELcum metric. Action proponents are
encouraged to incorporate as many factors, like full auditory weighting
functions, into their exposure models as possible.
Comment 95: One commenter suggested that NMFS include a more
detailed definition of the term ``narrowband,'' one that includes
explanatory text with regard to the derivation, terms and application
within the Guidance. Additionally, it was pointed out that NMFS is
incorrect to assume that narrowband sources will precisely adhere to
manufacture specifications and that harmonics or subharmonics are
unusual occurrences with these sources.
Response: NMFS agrees and has included additional clarification in
the Technical Guidance regarding the derivation and application of WFAs
in Appendix D (see Response to Comment 70). The term ``bandwidth'' is
defined in the Glossary (Appendix E). Additionally, based on this
comment, NMFS has revised the Technical Guidance to indicate harmonics
and sub-harmonics are almost always present and should be considered
when evaluating a source. The terms ``harmonics'' and ``sub-harmonics''
have also been added to the Glossary (Appendix E) of the Technical
Guidance.
24-Hour Accumulation Period
Comment 96: One commenter suggested the Guidance's
SELcum metric should require that the accumulation period be
based on the time an animal is or could be exposed to the sound and not
necessarily the time the noise occurs.
Along these same lines, the Commission noted that the accumulation
period should account for the biology, ecology, and ecological setting
(e.g., semi-enclosed bay, steep-sided underwater canyon) of the
affected animals and recommended that for activities that last at least
24 hours, NMFS consult with scientists and acousticians regarding the
applicability of an accumulation time for species that occur in a
confined or small geographic area during an extended period of time and
for activities that may affect resident populations or marine mammals
involved in certain behavior states (e.g., feeding, breeding/nursing,
socializing). Several other commenters provided similar examples and
made similar recommendations.
Response: NMFS agrees that the accumulation time associated with
SELcum metric should be based on the time the animal is
exposed, but notes that this can be exceedingly difficult if not
impossible or practical to determine (i.e., an animal's movement can
vary over space and time).
Further, NMFS acknowledges for exposure scenarios that occur in
confined geographic areas with resident populations, case-specific
modifications can be made, if appropriate, to the accumulation period
to capture the
[[Page 51717]]
potential for extended exposure periods for these populations. Various
factors could be considered, including consulting with scientists, if
appropriate.
Comment 97: One commenter expressed concern that implementing a
fixed accumulation period that is not based on physiology could have
unintended consequences. The commenter provided the example of when an
operation lasts for more than 24 hours, the use of a fixed 24-h
accumulation period may result in animals being ``taken'' multiple
times and that this may skew the risk assessment.
Response: The Technical Guidance focuses on predicting onset of PTS
and TTS, including consideration of energy accumulation. In the
regulatory context, NMFS acknowledges that the application of the
updated acoustic thresholds for quantifying take could result in
scenarios where an animal could be ``taken'' on multiple days (i.e., a
stationary source near resident animals; mobile source continuing over
multiple days), but this is no different from how take calculations are
done under the current thresholds, nor should it skew the broader
effects analysis. Ultimately, other factors would have to be taken into
consideration within a comprehensive effect analysis, including if the
same animals are exposed or ``taken'' on multiple days.
Comment 98: Several commenters recommended that the accumulation
period encompass the entire duration of an activity and suggested NMFS
revise the Technical Guidance to allow for the option of
SELcum modeling for the duration of the activity, in order
to allow action proponents the ability to utilize the approach with the
smallest estimated number of marine mammal exposures.
Response: NMFS determined the data currently available for deriving
acoustic thresholds do not support an accumulation period beyond 24
hours (e.g., available marine mammal TTS data are only available for
shorter duration exposures). Further, a key consideration in accurately
accumulating exposure beyond the recommended 24-h period is the ability
to accurately predict the location of the receiver relative to the
source. Again, the understanding of marine mammal distribution and
movement, especially during periods of sound exposure, is limited.
These data limitations hamper the ability to make realistic exposure
predictions for longer duration exposures. However, NMFS acknowledges
that there may be specific exposure situations where this accumulation
period requires adjustment and will work with action proponents to make
these adjustments (e.g., a resident population found in a small and/or
confined area; continuous stationery activity nearby an area where
marine mammals congregate, like a pinniped pupping beach). Finally,
NMFS recommends use of the approach that produces the most accurate
results for an activity (i.e., not necessarily the one that produces
the smallest or largest number of exposures).
Comment 99: Multiple commenters requested clarification as to
whether the Guidance accounts for the accumulation of sound from
multiple activities in the same area and multiple sources/phases
associated with a single activity. The commenters requested that an
alternative method/metric be developed for multiple sources active in
the same area at the same time (i.e., to better address cumulative
exposure associated with the entire soundscape). Specifically, the
Commission recommended that NMFS require action proponents use the
Guidance thresholds for determining the relevant isopleths associated
with activities that use multiple sound sources in the same area during
the same timeframe (e.g., multibeam echosounders and sub-bottom
profilers simultaneously with airguns during a seismic survey, various
types of sonar and/or impulsive sources used simultaneously during a
military exercise), rather than requiring action proponents to apply
the thresholds to discrete sources used during a specific activity.
Response: The Technical Guidance recommends application of the
SELcum metric to assess the impacts of noise on hearing for
individual activities/sources. Because current data available for
deriving acoustic thresholds are based on exposure to only a single
source, this metric is not intended for accumulating sound exposure
from multiple activities occurring within the same area or over the
same time or for multiple sources within a single activity. Currently,
NMFS is unaware of alternative metrics available to assess the impacts
of noise on hearing from multiple sound sources. As more data become
available, NMFS can re-evaluate the use of this metric for application
of exposure from multiple activities occurring in space and time. In
other contexts, such as masking, which is expected to occur at much
lower levels and much more likely to result from the contributions of
multiple sources, NMFS is supporting efforts to better assess the
impact of multiple sound sources on marine mammals (e.g., NOAA Ocean
Noise Strategy and CetSound Projects; National Research Council's Ocean
Studies Board's Cumulative Effects of Human Activities on Marine Mammal
Populations Study).
Comment 100: The Commission requested that NMFS provide additional
guidance on how action proponents unable to incorporate moving sources
should determine the total ensonified area (and consequently the number
of ``takes'') and recommended that action proponents unable to model
moving receivers and/or sources determined the total ensonified area
based on a model accumulating the energy for 24 hours and then
multiplying that ensonified area by the marine mammal density to
determine the total number of ``takes.'' The Commission's approach does
not assume a constant distance from the source, but rather a total
ensonified area associated with activity lasting 24 hours (or less if
appropriate) and a uniform density.
Response: Instead of the approach recommended by the Commission,
NMFS created a simple User Spreadsheet (released with Technical
Guidance) to aid action proponents in determining the isopleth
associated with their particular activity, if they are unable to employ
more sophisticated modeling techniques. The updated simple methodology
is based on the concept of ``safe distance'' presented in Sivle et al.
(2014) for moving sources, with more details presented in Appendix D of
the Guidance. The ``safe distance'' is equivalent to isopleths
applicants have calculated in the past, with area and marine mammal
exposures calculated by the same means (i.e., multiply isopleth times
marine mammal density) applicants have used with NMFS' current
thresholds (e.g., generic RMS SPL 180/190 dB).
Comment 101: One commenter requested clarification on several
questions related to the modeling of exposures using more and less
sophisticated methods: (1) Must a model be able to incorporate the
movement of both the source and the receivers or at least the receiver?
(2) How will NMFS determine whether an action proponent has the ability
to model moving receivers or not? (3) What will be the difference
between an action proponent employing more sophisticated modeling
capabilities versus those with less sophisticated capabilities?
Response: An action proponent is responsible for determining their
own modeling capabilities and, depending on the source and/or receiver,
this might include movement or not in order to recreate the most
realistic source-receiver separation (i.e., variation in spacing
between source and receiver over space and time). While NMFS does
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not require any particular models be used, they do evaluate the
appropriateness of models and associated methodologies used in
estimating acoustic exposures on a case-by-case basis in the context of
a proposed activity. NMFS has provided an optional User Spreadsheet for
action proponents unable to employ more sophisticated modeling on their
own. Generally speaking, because it intentionally includes multiple
conservative assumptions, we expect the simple, alternative method
generally will result in higher estimates of PTS-level exposure (which
in turn will translate into higher take estimates). A comprehensive
effects analysis for an action would take into consideration the fact
that the alternative method results in overestimates.
Comment 102: Several commenters indicated that the Guidance needs
to better address the potential of noise-induced hearing loss from more
continuous sources that operate 24 hours a day for multiple days (e.g.,
renewable energy wind farms/tidal operations; communication/navigation
beacons). Additionally, a commenter urged NMFS to consider
complementary devices operating synchronously in arrays as a continuous
sound source, rather than discrete sources. This same commenter
requested consideration for continuous noise sources having the
potential to displace an animal from critical feeding habitat.
Response: In U.S. waters, NMFS is aware of very few sources with
the potential of operating continuously (i.e., 24 hours a day, 7 days a
week, year-round). However, renewable energy platforms have the
capabilities for these types of continuous operations. NMFS
acknowledges that continuous operations can result in higher potential
for exposure accumulation, but the majority of renewable energy
operations produce relatively low levels of sound (i.e., close to
ambient, especially in environments conducive to wave or tidal devices;
e.g., Coping et al., 2014; Schuster et al., 2015) that even over an
accumulation period of 24-h are unlikely to exceed the PTS onset
thresholds. As for the operation of communication/navigation beacons,
these types of sources have a multitude of characteristics (e.g.,
source level, duty cycle, frequency band, beam width/orientation) but
generally have relatively short pulse lengths and produce higher
frequencies (i.e., greater ability for sound to attenuate) reducing the
likelihood of exposure resulting in cumulative effects. Finally,
regarding the comment about displacing an animal from critical feeding
habitat, the Technical Guidance focuses on the effects of noise on
marine mammal hearing and does not address displacement.
As previously addressed in a prior comment, because a sound
operates 24-h a day does not necessarily mean a receiver is exposed to
that source for that entire period (i.e., marine mammals are capable of
moving vertically or horizontally in the water column) or that it is
exposed to levels capable of inducing noise induced threshold shifts.
In other words, having an accurate understanding of the spatial and
temporal overlap between a source and receiver is important in being
able to accurately predict exposures.
Recovery
Comment 103: Multiple commenters recommended that the Guidance
consider data on marine mammal recovery from noise exposure.
Specifically, one commenter suggested the use of a ``leaky-integrator
model'' that accumulates sound energy and account for potential
physiological recovery in a time-dependent manner (described by a time
constant). The commenter indicated that the value of the time
constant(s) is not known but could be conservatively estimated.
Contrary to this comment, another commenter cautioned that recovery
times have generally been measured only during quiet periods within
laboratory settings and that in the open ocean, it is likely that free-
ranging animals will be exposed to sound during the recovery period.
Response: Recovery is an important consideration in assessing the
effects of noise on marine mammals, and the Technical Guidance includes
general information on recovery. We also agree recovery in the open
ocean is more complex than measured in a laboratory setting. Currently,
there are not enough data to directly take recovery into consideration
in the development of acoustic thresholds (and this is specifically
identified as a research recommendation in Appendix B), including the
integration of a ``leaky-integrator model.'' As more data become
available, NMFS can re-evaluate this issue. NMFS has provided
additional text in the Technical Guidance to address why recovery was
not directly considered in a quantitative manner. NMFS has also
provided more clarification in the text regarding recovery and the
Technical Guidance baseline accumulation period.
Comment 104: One commenter suggested that the Guidance's
accumulation period be ``reset'' to zero only when there has been a
sufficiently long silent period (i.e., not automatically after 24
hours). The commenter referred to NMFS' interim injury impact pile
driving criteria for fishes, which assumes that accumulation from zero
occurs only after a recovery period of 12 hours without sound exposure.
Response: NMFS' interim injury criteria for fishes pertain to
smaller pile driving activities (i.e., primarily associated with
construction) that only occur during daylight hours, where resetting
the accumulation period and allowing for a 12-h recovery period is
possible. However, some activities covered by the scope of this
Technical Guidance continue for longer than 24 hours (e.g., seismic
survey) and only resetting the accumulation after a sufficiently long
silent period (i.e., 12 to 24 hours) is not feasible. The data
currently available for deriving acoustic thresholds do not support an
accumulation period beyond 24 hours, and accumulating over the entire
activity duration (i.e., beyond 24 hours) could result in unrealistic
exposure results (e.g., difficult to predict the temporal and spatial
variability of a receivers over multiple days; see Response to Comment
79).
Comment 105: One commenter noted that if TTS and/or PTS are caused
by build-up of free radicals in the hair cell synapses (e.g., McFadden
et al., 2005), then exposure over extended periods must take the
clearance rate of the free radicals into consideration. The commenter
indicated that a 24-h period might be a reasonable approach based on
human audiometry but that given the absence of sufficient marine mammal
data, it may be necessary to consider SELcum over periods of
greater than 24 hours in situations where sources are loudest (e.g.,
large seismic airgun surveys) and propagation loss is lowest.
Response: NMFS acknowledges there are a multitude of factors that
affect recovery from noise-induced hearing loss, including clearance of
free radicals, making recovery complex. Further, there is a lack of
data, especially for marine mammals. That said, NMFS acknowledges there
may be some situations where the accumulation period needs to be
extended beyond 24 hours depending on case-specific scenarios. However,
these should be exceptions and not the norm (i.e., proposed
accumulations periods represent the typical exposure scenario; see
Response to Comment 79).
Comment 106: Multiple commenters expressed concern that several of
the recovery time lengths in the marine mammal TTS literature have been
reported to exceed 24 hours and
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indicate the Guidance's acoustic thresholds may not be sufficiently
conservative. Further, several commenters requested that NMFS consider
recovery in terms of exposure to other stressors, since these stressors
may exacerbate threshold shifts and/or recovery.
Response: NMFS acknowledges that recovery from noise exposure is
extremely complex and depends on a multitude of factors, which is why
recovery was not directly integrated into the Technical Guidance's
recommended accumulation period or into the acoustic thresholds. As
NMFS notes in the Technical Guidance, threshold shifts on the order of
the established PTS onset (i.e., 40 dB) recorded in marine mammal
laboratory studies have still resulted in recovery. Additionally, NMFS
has made several conservative assumptions in the development of its
acoustic thresholds (see Response to Comment 77). NMFS has added a
research recommendation relating to examining noise under realistic
exposure scenarios, including consideration of other stressors.
Comment 107: Several commenters suggested that the accumulation
period allow for the consideration of periods of reduced or no sound
(e.g., power-downs and line turns during seismic activities).
Response: NMFS agrees that power-downs associated with line turns
(not associated with mitigation, which can be unpredictable) should be
accounted for in modeling, particularly with the accumulation period
(i.e., total exposure period within a 24-h period, excluding periods
when there is no exposure).
Appendix D: Alternative Methodology (Formerly Identified as the User
Guide)
Comment 108: Several commenters indicated that the Guidance should
not be finalized until the public has been given the opportunity to
evaluate NMFS' user tools (i.e., having these tools is necessary to
perform a thorough analysis of the Guidance).
Response: NMFS disagrees. See Response to Comment 3.
Comment 109: It was suggested by a commenter that an alternative
method is unnecessary, as it is unlikely animals will remain close
enough to a source to exceed the Guidance's SELcum
thresholds (i.e., PK is anticipated to be the dominant metric,
resulting in the largest isopleth for most, if not all situations).
Response: NMFS disagrees that the PK should be assumed to be the
threshold resulting in the most conservative (i.e., largest) isopleth
for most sources. Furthermore, as a result of public comment, NMFS
decided to remove the PK thresholds for non-impulsive sounds. For
impulsive sounds, NMFS recommends an action proponent fully evaluate
their sound source to determine which metric would be dominant. NMFS
agrees it may be unlikely that animals would remain close to a source
for extended periods of time in most exposure situations. However,
predicting animal movement and distribution, especially during sound
exposure scenarios, is difficult. Finally, NMFS recognizes that in
updating our acoustic thresholds to reflect the best available science,
they have become more complex. Thus, Appendix D provides a set of
tools, examples, and weighting factor adjustments to allow action
proponents with different levels of exposure modeling capabilities to
reasonably approximate PTS onset, using the updated acoustic
thresholds, for all sound sources.
Comment 110: Several commenters requested NMFS explain how the
SELcum acoustic threshold should be used to determine if an
auditory impact would occur. Commenters recommended more guidance on
how this would be implemented for a couple of example projects (i.e.
stationary source such as pile driving, and moving source such as
seismic).
Response: Due to the diverse array of potential sound sources, it
is impractical for NMFS to provide specific, detailed example
calculations within the Technical Guidance. However, NMFS is providing
a simple optional User Spreadsheet to aid action proponents unable to
perform more sophisticated exposure modeling. This spreadsheet
specifically provides a means of applying the Technical Guidance's
thresholds and simplified weighting (WFAs) and calculates isopleths
associated with thresholds expressed as SELcum. Thus,
example calculations can be completed by using the optional User
Spreadsheet. Those using more sophisticated models (e.g., animats)
would presumably have some other means of accounting for cumulative
exposure, like an ``acoustic dosimeter,'' and would not necessarily
need to determine a SELcum threshold distance (see Response
to Comment 114).
Comment 111: Concern was expressed by several commenters that the
alternative methodology provided in Appendix D would limit flexibility
to assess the impacts of noise on marine mammal hearing.
Response: Action proponents are not obligated to use the
alternative methodology and may perform more sophisticated modeling or
consider additional action- or location-specific factors, if able.
Thus, action proponents are given flexibility in terms of their
exposure modeling.
Comment 112: Several commenters were concerned that the highly
technical nature of the Guidance does not lend itself to direct and
consistent application, particularly by non-experts and indicated that
alternative methodology could result in more restrictive acoustic
criteria for the smaller action proponents.
Response: NMFS has produced an associated simple optional User
Spreadsheet that has been finalized with the Technical Guidance to
assist stakeholders in applying the updated acoustic thresholds
associated with the more complex SELcum thresholds,
including tools to help those that cannot incorporate more complicated
auditory weighting functions (see Response to Comments 70 and 100).
NMFS acknowledges that less sophisticated exposure models may
result in higher exposure estimates because these models do not
incorporate as many factors as more sophisticated models. Action
proponents are encouraged to incorporate as many appropriate factors
into their modeling as possible. An action proponent is not obligated
to use the simpler tools provided by NMFS, if they can provide equally
or more realistic exposure modeling on their own.
Comment 113: One commenter noted that the NMFS' West Coast Region
provides a SELcum calculator for estimating impacts to
fishes during impact pile driving, including the incorporation of an
``effective quiet'' value, and requested a similar calculator be
provided for marine mammals. The commenter recommended a consistent
process for accumulating energy and assessing impacts to all species
under NMFS' purview.
Response: The Technical Guidance provides a similar
SELcum calculator for marine mammals, but effective quiet
will not be directly incorporated into the marine mammal calculator
because NMFS determined there are not enough data at this time to do
so. NMFS believes it is consistent in how it assesses acoustic impacts
for the various species under its jurisdiction but, there may be
exceptions that depend on various factors (e.g., species-specific
considerations, data availability, etc.).
Model Specifications
Comment 114: Multiple commenters indicated that the Guidance
suggests that a variety of model approaches could be employed in
applying the Guidance's acoustic thresholds. Instead, the commenters
suggested that NMFS
[[Page 51720]]
recommended standardized computer models or modeling requirements,
which would allow regulators, industry, and the public to run
repeatable analysis to verify acoustic data based on NMFS'
recommendations. The commenters expressed concern that it is likely
that both the current range of modeling vendor choices and their
capacity will be inadequate to fulfill the agency's requirements, which
could lead to unwarranted permitting delays or costs, and suggested a
transition period to necessitate the expansion of the pool of adequate
modeling expertise and vendors. Finally, a commenter recommended that
NMFS undertake model validation/verification as part of the process of
developing the final acoustic criteria.
Response: Providing standard computer models for analysis or
modeling requirements associated with the application of the Technical
Guidance's acoustic thresholds and/or auditory weighting functions, as
well as model validation/verification, is beyond the scope of this
exercise. The adequacy of models will depend on a multitude of factors,
including the activity (source) and potential receivers. Because the
updated acoustic thresholds are more complex, simpler alternatives have
been provided (e.g., User Spreadsheet with weighting factor adjustments
for those unable to fully incorporate auditory weighting functions),
which can be used until the pool of adequate modeling expertise is
expanded. Further, NMFS recognizes there will be a transition period
before the Guidance is fully used. (See previous section in this Notice
on Transitioning to the Technical Guidance).
Comment 115: The Commission recommended that the Guidance provide
specifications necessary to perform exposure modeling. They indicate
that it is NMFS' responsibility, as a regulatory agency, to make
required findings and direct action proponents to the appropriate types
of models, including inputs and appropriate factors to be considered
within those models.
Response: NMFS does not currently provide modeling specifications
and has no current plans to do so. NMFS will provide some technical
assistance to prospective applicants who request it and will continue
to evaluate the models that are used in submitted compliance documents
to ensure they are adequate and appropriate.
Comment 116: The Commission commented on the two alternative models
(i.e., one for moving sources and one for stationary sources) provided
in the 2015 Draft Guidance Appendix D. Specifically, the Commission
requested that more information be provided whether the 3-D ``safe
distance'' methodology of Sivle et al. (2014) for moving sources is
applicable to NMFS' 2-D application specified in the Guidance. The
Commission requests this aspect be submitted for peer review.
BOEM expressed concern that the methodology of Sivle et al. (2014)
is not appropriate for directional sources or for receivers that are
not at the same depth as the source (e.g., sperm whales). The Guidance
states that this methodology is independent of exposure duration, and
BOEM states this is inconsistent with the document's recommendation of
a 24-h baseline accumulation period. Further, BOEM recommended that
this method include a representative depth typical of the species being
modeled.
Response: NMFS reiterates that the two models referred by the
Commission are alternative methods. Action proponents are not obligated
to use these methods. Although Sivle et al. (2014) accounted for the
depth of herring to determine the percent of the winter and summer
populations exceeding the ``safe distance'' associated with exposure to
naval sonar, the calculation of ``safe distance'' (i.e., equations in
the Technical Guidance) makes minimal assumptions associated with the
receiver (i.e., the receiver is stationary and does not exhibit
avoidance or attraction to the source) and does not directly account
for receiver depth or density. It only provides the distance from the
source (i.e., isopleth) beyond which a threshold is exceeded. Thus,
NMFS believes that this methodology is appropriate for 2-D
applications. NMFS has added information about the assumptions
associated with the receiver within the Technical Guidance for clarity.
NMFS does not believe additional peer review is need for this aspect of
the Technical Guidance because the methodology (Sivle et al., 2014) has
already undergone peer review as part of its publication in ICES
Journal of Marine Science.
Addressing concerns raised by BOEM, it is correct that the methods
of Sivle et al. (2014) may not be representative for directional
sources and are likely to result in more conservative exposures (i.e.,
model does not account for source directivity and isopleths produced
assume an omnidirectional source; meaning that it produces an isopleth
equal in all directions). However for directional sources, the source
level parameter associated with this methodology assumes the values
provided are those relating to the direction producing the maximum
level. Again, this optional methodology does not make any assumptions
about the depth of the receiver: it only provides an isopleth
associated with a particular acoustic threshold. It is possible that
the depth of the receiver can accounted for in terms of depth-dependent
density (i.e., percentage of time species is located at a particular
depth). However, accounting for specific characteristics associated
with the receiver (e.g., depth distribution, density, behavioral
response, etc.) is beyond the scope of this document.
Finally, the reason this optional methodology is independent of
exposure duration is because it only considers one pass of the source
relative to receiver, with the closest points of approach incurring the
greatest accumulation (i.e., once the source moves past the closest
point of approach accumulation is only further reduced as the source
moves farther and farther away). Accumulating past the recommended 24-h
accumulation period does not result in the addition of any significant
amount to the cumulative sound exposure of the receiver. The model can
be adjusted to account for shorter accumulation periods. However, the
equations become more complex and more difficult to implement.
Comment 117: Several commenters expressed concerns over a potential
short-coming associated with the optional ``safe distance'' method
(Sivle et al., 2014) accounting for cumulative exposure for moving
sources, specifically its ability to allow only for the inclusion of
spherical spreading as a propagation model. It was suggested that other
propagation models, especially those more conservative spreading models
associated with shallow water, need to be incorporated into this
methodology. Related to this, BOEM indicated that the Guidance's
``source factor'' definitions closely resembled cylindrical spreading
(10\TL\/\10\), rather than spherical spreading
(10\TL\/\20\) and expressed a concern over whether Mean
Squared Pressure (MSP) or Equivalent Plane Wave Intensity (EPWI) terms
were used, and that the terms ``S,'' ``SE,'' and ``E0'' in the Guidance
appear to have similar units, but they do not.
Additionally, these commenters provided an example to assess the
appropriateness of the ``safe distance'' methodology by examining the
modeled radii from four parallel passes, within a 24-h period, from a
3300 cubic inch airgun. Based on their modeling, it was suggested that
NMFS lower thresholds for LF cetacean and PW pinnipeds, raise
thresholds for HF cetaceans, and adjust the same distance methodology
to
[[Page 51721]]
account for the number of passes within an area during a 24-h period.
There was no detail provided by the commenter on what these adjustments
should be.
Response: NMFS acknowledges the concerns and potential limitations
of the optional ``safe distance'' methodology but believes other
assumptions associated with this methodology ensure as a whole it
remains precautionary. The incorporation of other types of spreading
models results in a more complicated equation making the methodology
less easy to implement. However, many mobile sources, like seismic
airguns or sonar, produce sound that is highly-directional (i.e., most
of time sound source is directed to the ocean floor, with less sound
propagating horizontally, compared to the vertical direction), and
directionality is not accounted for with this methodology (see Response
to previous comment). Additionally, many higher-frequency sounds, like
sonar, are also attenuated by absorption, which is also not taken into
account in this methodology. Thus, there are other considerations
beyond spherical spreading, including other conservative factors (i.e.,
simplified incorporation of auditory weighting factors, the receiver
does not avoid the source, etc.) to consider when assessing whether the
use of this optional methodology will result in a potential
underestimate of exposure. Thus, despite these simple assumptions, NMFS
believes the optional ``safe distance'' approach offers a better
approximation of the source-receiver distance over space and time for
various mobile sources than choosing a set accumulation period for all
sources, which assumes a fixed source-receiver distance over that time,
and encourages the development/validation of alternative models,
including the assessment optional models provided in the Technical
Guidance (see Appendix B: Research Recommendations).
As for BOEM's comments regarding MSP vs. EPWI terms, by following
ANSI definitions within the Guidance, NMFS is implicitly using MSP
terms. The term ``source factor'' within the Guidance is based on a
source level being defined as pressure squared, which why it may appear
to resemble cylindrical spreading, rather than spherical spreading.
This additional information was added to provide clarity. BOEM is
correct that the terms ``S,'' ``SE,'' and ``E0'' that appear in the
Technical Guidance do not have identical units. NMFS understands the
potential confusion, since this information was not included in the
2015 July Draft Guidance. A section has been added in Appendix D
providing these units in the Technical Guidance (i.e., See section
3.2.1.1 Linear Equivalents).
In response to the commenter's modeled example, NMFS disagrees with
the appropriateness of this comparison. One of the assumptions
associated with the optional ``safe distance'' methodology is that the
source moves at a constant speed and in a constant direction. Thus,
this model is not sophisticated enough to account for situations for
multiple passes and should not be used for these situations (i.e., NMFS
would recommend an action proponent in this situation to find a more
appropriate means of modeling exposure, or work with NMFS to determine
if the ``safe distance'' methodology can be appropriately modified to
account for multiple passes from a source). Thus, it is not unexpected
that there are several discrepancies between the commenter's modeled
isopleths and those provided by the ``safe distance'' method, including
the use of different weighting functions and thresholds, by the
commenter, compared to those in the Technical Guidance. NMFS believes
the Technical Guidance represents the best available science and
disagrees that adjustments to the document's acoustic thresholds is
supported.
Technical Guidance Implementation and Regulatory Context
Comment 118: One commenter recommended that the Guidance solely
focus on providing the technical basis for acoustic thresholds (i.e.,
best available science) rather than containing substantial
implementation language in the document. The commenter indicated that
limiting the purpose of the Guidance to solely providing technical
background would allow flexibility to incorporate new technologies and
information as they become available.
Response: NMFS agrees and revised the title of the Guidance to
reflect its technical, scientific nature. The Technical Guidance is a
compilation, interpretation, and synthesis of the available literature.
Application of the updated acoustic thresholds remains consistent with
current NMFS practice. That information on regulatory context has been
moved to this Notice. Any changes to application in the regulatory
context are separate from the basis for updating the thresholds
themselves, where advances in scientific knowledge are the drivers.
Comment 119: One commenter requested the Technical Guidance provide
a brief reference to its use in the current 14-question MMPA incidental
take application.
Response: The Technical Guidance is a compilation, interpretation,
and synthesis of the scientific literature on the impacts of sound on
marine mammal hearing. There is no change to the use of thresholds in
the regulatory context. No specific reference is required in our
implementing regulations.
Comment 120: One commenter noted that the MMPA mandates that
``Level A'' harassment includes not only the actual or likely onset of
injury, but also the potential for injury and that the ESA definition
of ``harm'' encompasses temporary injuries or impairments that impact
essential behavior. The commenter expressed concern that setting the
threshold for ``Level A'' harassment under the MMPA and ``harm'' under
the ESA at the actual onset of injury is inconsistent with the
statutory mandates, which seek to protect against the risk of, or
potential for, injury and recommended that NMFS must set a protective
threshold in order to comply with its statutory mandates (i.e., one
that interprets the existing literature conservatively enough to
reflect the potentiality of harm).
Response: The Technical Guidance auditory impact thresholds were
based on scientifically-based judgments, including accounting for
uncertainty and variability, developed to stand independent of
interpretations of statutory terms such as ``take,'' ``harm,'' and
``harassment.'' At the same time, the thresholds were designed for use
in NMFS' regulatory analyses.
NMFS incorporated several conservative assumptions in the
development of the PTS onset thresholds to account for the potential
for PTS onset (see Response to Comment 77). Further, there are several
examples of marine mammal exposure exceeding the Guidance's PTS
thresholds, where recovery has occurred (see recent review in Finneran
2015).
Comment 121: Several commenters provided examples of how the
weighting function and thresholds compare to data collected in the
field during SSV measurements (e.g., seismic and impact piled driving).
The commenters' analysis operated on the assumption that the weighting
functions and thresholds should provide equal results when compared to
the weighting functions and thresholds in Southall et al. (2007), and
argued that results stemming from the Guidance ``did not yield the most
reliable or cautionary results.'' In one example, it is stated that
these comparisons are ``at odds with the
[[Page 51722]]
reports of the sensitivity of beaked whales to pulsed sounds.''
Response: NMFS appreciates the commenter's efforts to provide
examples and comparisons using the Technical Guidance. However, we
disagree that the Technical Guidance must yield similar results to
those provided in Southall et al. (2007), since available data and
methodology has significantly evolved since 2007. For example, marine
mammal weighting functions (M-weighting) from Southall et al. (2007)
were derived in a more simplistic manner than the updated methodology
provided in Appendix A, which directly uses audiogram and TTS data to
derive weighting functions. Thus, the Southall et al. (2007) M-
weighting functions are broader than those provided in the Technical
Guidance and would inherently result in larger, more conservative
isopleths. Although the isopleths derived using the Technical Guidance
results are smaller in comparison to those from Southall et al. (2007),
they are not necessarily unreliable.
In addition, NMFS is aware that the Southall et al. (2007) panel is
in the process of updating its paper. It is anticipated that their
proposed weighting functions will not be as broad (most susceptible
frequency range) as their original M-weighting functions (i.e., they
will be more aligned with those presented in the Technical Guidance).
Regarding beaked whale sensitivity, NMFS agrees these species are often
classified as a ``particularly sensitive'' group, but in the context of
behavioral responses. The Technical Guidance does not pertain to
behavioral responses, only effects of noise on hearing. The assumption
that this enhanced sensitivity carries over to hearing and
susceptibility to noise-induced hearing loss is currently unsupported
by beaked whale AEP measurements (e.g., Finneran et al., 2009; Pacini
et al.. 2011) or transmission pathway modeling (e.g., Cranford et al.,
2008) .
Comment 122: Several commenters remarked that the Guidance does not
explain the anticipated impact of the acoustic thresholds on the
regulated community. Because the Guidance will be applied in a range of
regulatory actions, it was recommended that NMFS undertake a study
comparing the assessment approach described in the Guidance with the
current assessment methods to demonstrate the regulatory implications
of the proposed acoustic thresholds.
Response: The Technical Guidance represents the culmination of a
robust assessment of the scientific literature to derive updated,
science-based auditory impact thresholds for marine mammals. The
overall assessment approach in the regulatory context has not changed
from current agency practice.
The acoustic thresholds presented in the Technical Guidance use
different metrics compared to the current thresholds. In some
situations, depending on the sound source, species of interest, and
duration of exposure, application of the updated acoustic thresholds
may result in greater estimates of PTS (and therefore more ``takes'')
than under the existing thresholds, while in other situations the
opposite result may occur. Examining all possible scenarios associated
with the wide range of potential activities is not feasible.
Comment 123: Multiple commenters expressed concern that the
Guidance will unnecessarily result in an increased burden to action
proponents during the permitting process and would lead to an increased
number of shutdowns or longer survey duration, with increased costs and
safety risks.
Response: NMFS recognizes the advancing science on auditory impacts
has led to more complex set of thresholds and methodology for
evaluating impacts and has provided a simplified alternative
methodology to alleviate some of the burden associated with applying
the more complex acoustic thresholds and auditory weighting functions.
In terms of effects on activities themselves, the Guidance does not
address consequences for mitigation requirements in a regulatory
context. This will depend on the particular aspects of an action,
taking into account the comprehensive effects analysis and regulatory
considerations. NMFS notes that there are no requirements that
mitigation measures directly correspond to acoustic thresholds (See
Response to Comment 11).
Comment 124: One commenter expressed concern that applying the
alternative methods provided in the Guidance could result in
unrealistically high exposure estimates. The commenter recommended that
the Guidance include more explanation to inform action proponents about
the potential costs, benefits, and consequences of methodologies that
directly use auditory weighting functions and those that do not
(alternative methods).
Response: NMFS notes it will be an action proponent's decision as
to how they model and estimate their potential impacts to marine
mammals. Analyzing the potential cost/benefits of the methodologies
applied is beyond the scope of the document and will vary depending on
the activity/sound source and species impacted. The optional WFAs
provided in the Technical Guidance should assist action proponents with
incorporating auditory weighting functions and should provide very
similar (if not identical) results for narrow-band sources and larger
isopleths for broadband sources, depending on how much information the
action proponent can provide regarding the frequency composition of
their source (i.e., can provide the 95 percent frequency contour
percentile or rely on the more conservative default WFA values).
Comment 125: Multiple commenters requested more information on how
NMFS will transition from previously applied thresholds to the acoustic
thresholds provided in the Guidance (e.g., how will it affect
applications/consultations completed, in process and beyond) and
expressed concerned over the potential for delays and NMFS' time
requirements to process permits based on the Guidance.
Further, one commenter remarked that NMFS' intention to update the
acoustic thresholds based on newly available information is valid from
a scientific point of view, but from a practical aspect could be
confusing, could promote regulatory uncertainty, and has the potential
to affect permitting timelines. The commenter indicated that planning
for certain activities can take multiple years to complete, with the
introduction of additional uncertainty potentially adversely affecting
the ability of action proponents to plan for and comply with the
Guidance.
Similarly, several commenters requested clarification as to how the
Guidance would be implemented in (a) the context of a five-year
incidental take regulation (ITR) (with specific take authorizations by
letters of authorization (LOA)) and (b) when numerous IHAs are issued
for a given area in the absence of an ITR. Specifically, a commenter
asked if different methods will be used to estimate the amount of
authorized incidental ``take'' in each of these contexts and how, if at
all, will authorized ``take'' be allocated over certain periods of time
in one or both of these contexts?
Response: NMFS acknowledges there will be some lag between updates
in the best available information and the ability to incorporate that
new information into ongoing processes. We refer readers to the section
of this Notice addressing Transitioning to the
[[Page 51723]]
Technical Guidance for more information.
Comment 126: One commenter suggested that the Guidance provides an
opportunity for NMFS to clarify its policy on ``takes'' vs. ``animals
taken.'' The commenter indicated that just because an animal is
``exposed'' to a sound source does not necessarily equate to a ``take''
or an impact as defined in the MMPA and provided the following example
with migratory (e.g., 50 takes with individuals being taken once) vs.
resident species (e.g., 50 takes with ten individuals being taken five
time each). Similarly, a commenter requested that NMFS should clarify
that, in estimating numbers of auditory impacts for management
purposes, take numbers will be calculated for each day of exposure and
then added to obtain the total estimate. For example, assuming an equal
daily risk of eight exposures that exceed PTS thresholds for some
species over a 10-day pile-driving project, the total potential PTS-
level take would be 80 animals. The Navy has long employed this method
of calculation, but its use by other applicants (e.g., seismic
operators) has been inconsistent. Notably, this method would not
account for multiple takes of individual marine mammals and the
cumulative impact on hearing that would result from those takes.
Response: The Technical Guidance is designed for assessing the
impact of underwater noise on marine mammal hearing by providing
scientifically-based auditory weighting functions and acoustic
thresholds. It does not address how to calculate takes in various
situations. Those considerations are case-specific and based on
multiple considerations, including spatial and temporal overlap between
the sound source and a receiver). Moreover, factors like whether a
marine mammal species or stock is migratory or resident (among numerous
other factors), are considered within a broader comprehensive effects
analysis when such information is available.
Comment 127: The Commission commented that the Guidance states that
an alternative approach may be proposed (by federal agencies or other
action proponents) and used if case-specific information or data
indicate that the alternative approach is likely to produce a more
accurate estimate of Level A Harassment, harm, or auditory injury for
the proposed activities. Such a proposed alternative approach may be
used if NMFS determines that the approach satisfies the requirements of
the applicable statutes and regulations. The Commission noted that NMFS
has not provided any criteria under which such an exception could be
invoked and is allowing action proponents to waive the Guidance's
acoustic thresholds. The Commission does not support this approach and
recommends that NMFS require all action proponents to implement the
final acoustic thresholds until such time that they are amended or
revised by NMFS.
Similar to the Commission's concerns, another commenter indicated
any alternative approach must be at least as protective as methods
prescribed in the Guidance, which have at least undergone peer review
and public notice and comment. Alternatively, the commenter suggested
that more conservative approaches should be used if a project's
circumstances require a lower threshold for ``take'' based on specific
factors, such as geographic region, oceanographic conditions, low
abundance, species site fidelity, prey impacts or cumulative impacts.
Contrary to the comments above, a few commenters indicated that
they welcome the opportunity for action proponents to propose
alternative approaches to those presented in the Guidance. The
commenters noted that this flexibility will enable innovation within
the bounds of regulatory compliance and that are appropriate and
justified (e.g., there are many ways to estimate potential exposures of
marine mammals to various sound levels).
Response: The Technical Guidance is not a regulation or rule. It
does not create or confer any rights for or on any person, or operate
to bind the public. However, it is NMFS' assessment of the best
available information for determining auditory impacts from exposure to
anthropogenic sound and it has undergone extensive peer and public
review. With that in mind, NMFS agrees with the comment that any
alternative approach should be peer reviewed before it is used instead
of the updated thresholds in the Technical Guidance (or the alternative
methodology). With that addition to NMFS' statement in the Draft
Guidance, an alternative approach that has undergone independent peer
review may be proposed if in NMFS' view it ``is likely to produce an
equally or more accurate estimate of auditory impacts for the project
being evaluated, if NMFS determines the approach satisfies the
requirements of the applicable statutes and regulations.'' NMFS
believes this sets a fairly high bar as to what type of data/
alternative approach would justify a departure from the Guidance's
auditory weighting functions and/or acoustic thresholds, especially in
terms of the HISA standards to which this Guidance adheres.
Additionally, action proponents are afforded flexibility for factors
beyond the Guidance's auditory weighting functions and/or acoustic
thresholds (e.g., propagation modeling, exposure modeling) as a means
to accurately predict and assess the effects of noise on marine
mammals.
Comment 128: Multiple commenters requested flexibility associated
with the accumulation period, especially for projects with a stationary
source and for action proponents with limited ability to conduct
detailed modeling (e.g., pile driving projects). The commenters
recommended that NMFS allow for the flexibility to make project-
specific adjustments based on physical or biological factors associated
with the activity.
Response: NMFS acknowledges that all action proponents may not have
the same level capabilities to apply the Technical Guidance and has
provided an optional User Spreadsheet for action proponents that wish
to avail themselves of it. Additionally, NMFS recognizes there may be
some situations where project-specific modification may be necessary
(i.e., action proponent should contact NMFS to discuss project-specific
issues that are beyond scope of Technical Guidance).
Comment 129: One commenter expressed concern that the updated
acoustic thresholds could underestimate instances of PTS/TTS from
permitted activities because marine mammals can be elusive and
observations from protected species observers are few in relation to
the estimated abundance. Similarly, one commenter asked how the
acoustic thresholds would be used to calculate ``take'' after an
activity is completed.
Response: The acoustic thresholds are just one tool used to predict
``take'' calculations. Other factors (e.g., sound propagation or marine
mammal density/occurrence) contribute to these calculations though they
are beyond the scope of the Technical Guidance. NMFS notes that the
Technical Guidance's intended purpose is as a tool for predicting
potential impacts of noise on hearing before an activity occurs (and
perhaps afterward).
Comment 130: The Commission requested clarification on how and when
action proponents should use the qualitative factors identified within
the Guidance and expressed concern that these factors could be used to
allow for a reduction in ``take'' estimates based on subjective
judgments rather than best available science. The Commission
recommended that NMFS remove the list of qualitative factors listed and
incorporate it by reference in the text and not allow action proponents
to use
[[Page 51724]]
those factors to modify isopleths or numbers of ``takes'' resulting
from the quantitative thresholds.
Response: NMFS' intent of providing qualitative factors for
consideration was to acknowledge that when additional data may become
available in the future; these additional factors may be incorporated
with quantitative PTS onset thresholds. At this time, however, it is
not NMFS' intent for these factors to reduce quantitative exposure
estimates based on subjective judgment. The Technical Guidance
acknowledges that these factors are important for consideration within
the comprehensive effects analysis on a qualitative basis. To avoid
confusion, NMFS removed the list of qualitative factors from the
threshold tables and placed this information in Appendix B: Research
Recommendations.
Miscellaneous Issues
Comment 131: One commenter requested clarification was on how much
an acoustic threshold would need to change to update the Technical
Guidance and suggested updates only occur when thresholds change by at
least 5 dB.
Response: NMFS has provided a procedure and timeline for updating
the Guidance (Section III of main Guidance document) and will evaluate
new studies as they become available, including in the context of
existing data, before determining the impact to the acoustic
thresholds.
Comment 132: One commenter recommended the Guidance include a table
indicating a species' hearing ability, sound production
characteristics, and genetic relatedness to other species in order to
determine when there are enough individuals of a particular species or
genus to warrant species- or genus-specific acoustic thresholds, rather
than relying on hearing group thresholds.
Response: NMFS has used the best available science to support the
division marine mammals into five hearing groups, including the
derivation of composite audiograms based on available hearing data, and
declines to include the requested table as it goes beyond the scope of
the Technical Guidance. As science progresses (i.e., more data on
hearing, sound production, genetics become available), NMFS will
determine if further refinements of hearing groups and their associated
auditory thresholds are needed.
Comment 133: Several commenters requested that additional terms be
better defined in the Guidance (e.g., isopleth, narrowband, roll-off,
equal latency).
Response: NMFS has added and defined these terms in the Glossary
(Appendix E) and/or provided more clarification within the Technical
Guidance.
Comment 134: A few commenters suggested improvements to the
Guidance, including technical editing, literature citation
verification, and the inclusion of more plain language.
Response: NMFS has verified that all references used in the
Technical Guidance appear in the Literature Cited section and has
included more plain language, when possible. However, NMFS notes this
is a highly technical document, with most of the terms not easily
subjected to plain language revisions without altering the accepted
meaning of those terms. Additionally, definitions for technical terms
used in this document are defined in the Glossary (Appendix E).
Dated: July 29, 2016.
Donna S. Wieting,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. 2016-18462 Filed 8-3-16; 8:45 am]
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