[Federal Register Volume 78, Number 132 (Wednesday, July 10, 2013)]
[Notices]
[Pages 41371-41384]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2013-16601]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[Docket No. 1206013117-3579-02]
RIN 0648-XA768
Endangered and Threatened Wildlife; Determination on Whether To
List the Ribbon Seal as a Threatened or Endangered Species
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice of a listing determination and availability of a status
review document.
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SUMMARY: We, NMFS, have completed a comprehensive status review of the
ribbon seal (Histriophoca fasciata) under the Endangered Species Act
(ESA). Based on the best scientific and commercial data available,
including the Biological Review Team's (BRT's) status review report, we
conclude that listing the ribbon seal as threatened or endangered under
the ESA is not warranted at this time. We also announce the
availability of the ribbon seal status review report.
DATES: This listing determination was made on July 10, 2013.
ADDRESSES: The ribbon seal status review report, as well as this
listing determination, can be obtained via the internet at http://alaskafisheries.noaa.gov/. Supporting documentation used in preparing
this listing determination is available for public inspection, by
appointment, during normal business hours at the office of NMFS Alaska
Region, Protected Resources Division, 709 West Ninth Street, Room 461,
Juneau, AK 99801. This documentation includes the status review report,
information provided by the public, and scientific and commercial data
gathered for the status review.
FOR FURTHER INFORMATION CONTACT: Tamara Olson, NMFS Alaska Region,
(907) 271-5006; Jon Kurland, NMFS Alaska Region, (907) 586-7638; or
Marta Nammack, NMFS Office of Protected Resources, (301) 427-8469.
SUPPLEMENTARY INFORMATION:
Background
On December 20, 2007, we received a petition from the Center for
Biological Diversity (CBD) to list the ribbon seal as a threatened or
endangered species under the ESA, primarily due to concern about
threats to this species' habitat from climate change and
[[Page 41372]]
resultant loss of sea ice. The Petitioner also requested that critical
habitat be designated for ribbon seals concurrently with listing under
the ESA. On March 28, 2008, we published a 90-day finding (73 FR 16617)
in which we determined that the petition presented substantial
information indicating that the petitioned action may be warranted and
initiated a status review of the ribbon seal. On December 30, 2008, we
published our 12-month finding and determined that listing of the
ribbon seal was not warranted (73 FR 79822).
On September 3, 2009, CBD and Greenpeace, Inc. (collectively,
``Petitioners'') filed a complaint in the U.S. District Court for the
Northern District of California challenging our 12-month finding. On
December 21, 2010, after considering cross-motions for summary
judgment, the Court denied the Petitioners' motion for summary judgment
and granted NMFS's cross-motion. The Petitioners filed a notice of
appeal of this judgment to the Ninth Circuit Court of Appeals on
January 18, 2011.
Information became available since publication of the December 30,
2008, 12-month finding that had potential implications for the status
of the ribbon seal relative to the listing provisions of the ESA,
including new data on ribbon seal movements and diving, as well as a
modified threat-specific approach to analyzing the ``foreseeable
future'' which we used in status reviews for spotted (Phoca largha),
ringed (Phoca hispida), and bearded seals (Erignathus barbatus) that we
completed subsequent to the ribbon seal status review (75 FR 65239,
October 22, 2010; 77 FR 76706 and 77 FR 76740, December 28, 2012). In
consideration of this information, on August 30, 2011, we agreed to
initiate a new status review and issue a determination on whether
listing the ribbon seal as threatened or endangered is warranted and
submit a determination to the Office of the Federal Register by
December 10, 2012. In addition, under the terms of this agreement,
following publication of the new listing determination in the Federal
Register, the Petitioners will file a motion for voluntary dismissal of
its appeal of the December 21, 2010, judgment. We announced the
initiation of this status review on December 13, 2011 (76 FR 77467).
Subsequently, NMFS and the other parties to this agreement agreed to
change the 12-month deadline to July 10, 2013.
The 2013 status review report for the ribbon seal (Boveng et al.,
2013) is a compilation of the best scientific and commercial data
available concerning the status of the species, including
identification and assessment of the past, present, and foreseeable
future threats to the species. The BRT that prepared this report was
composed of eight marine mammal biologists, two fishery biologists, and
a climate scientist from NMFS's Alaska and Southwest Fisheries Science
Centers and NOAA's Pacific Marine Environmental Laboratory. The status
review report underwent independent peer review by three scientists
with expertise in marine mammal biology and ecology, including
specifically ribbon seals.
ESA Statutory, Regulatory, and Policy Provisions
Section 3 of the ESA defines a ``species'' as ``any subspecies of
fish or wildlife or plants, and any distinct population segment of any
species of vertebrate fish or wildlife which interbreeds when mature.''
Section 3 of the ESA further defines an endangered species as ``any
species which is in danger of extinction throughout all or a
significant portion of its range'' and a threatened species as one
``which is likely to become an endangered species within the
foreseeable future throughout all or a significant portion of its
range.'' Thus, we interpret an ``endangered species'' to be one that is
presently in danger of extinction. A ``threatened species,'' on the
other hand, is not presently in danger of extinction, but is likely to
become so in the foreseeable future (that is, at a later time). In
other words, the primary statutory difference between a threatened and
endangered species is the timing of when a species may be in danger of
extinction, either presently (endangered) or in the foreseeable future
(threatened). Under section 4(a)(1) of the ESA, we must determine
whether a species is threatened or endangered because of any one or a
combination of the following factors: (A) The present or threatened
destruction, modification, or curtailment of its habitat or range; (B)
overutilization for commercial, recreational, scientific, or
educational purposes; (C) disease or predation; (D) inadequacy of
existing regulatory mechanisms; or (E) other natural or human-made
factors affecting its continued existence. We are to make this
determination based solely on the best scientific and commercial data
available after conducting a review of the status of the species and
taking into account those efforts being made by states or foreign
governments to protect the species. In judging the efficacy of
protective efforts not yet implemented or not yet shown to be
effective, we rely on the joint NMFS and FWS Policy for Evaluating
Conservation Efforts When Making Listing Decisions (68 FR 15100; March
28, 2003).
Two key tasks are associated with conducting an ESA status review.
The first is to identify the taxonomic group under consideration; and
the second is to conduct an extinction risk assessment which will be
used to determine whether the petitioned species is threatened or
endangered.
To be considered for listing under the ESA, a group of organisms
must constitute a ``species,'' which section 3(16) of the ESA defines
to include ``any subspecies of fish or wildlife or plants, and any
distinct population segment of any species of vertebrate fish or
wildlife which interbreeds when mature.'' The term ``distinct
population segment'' (DPS) is not commonly used in scientific
discourse, so the U.S. Fish and Wildlife Service (FWS) and NMFS
developed the ``Policy Regarding the Recognition of Distinct Vertebrate
Population Segments Under the Endangered Species Act'' to provide a
consistent interpretation of this term for the purposes of listing,
delisting, and reclassifying vertebrates under the ESA (61 FR 4722;
February 7, 1996). We describe and use this policy below to guide our
determination of whether any population segments of this species meet
the DPS criteria established in the policy.
The foreseeability of a species' future status is case specific and
depends upon both the foreseeability of threats to the species and
foreseeability of the species' response to those threats. When a
species is exposed to a variety of threats, each threat may be
foreseeable over a different time frame. For example, threats stemming
from well-established, observed trends in a global physical process may
be foreseeable on a much longer time horizon than a threat stemming
from a potential, though unpredictable, episodic process such as an
outbreak of disease that may never have been observed to occur in the
species.
Since completing the 2008 status review of the ribbon seal (Boveng
et al., 2008), with its climate impact analysis, NMFS scientists have
revised their analytical approach to the foreseeability of threats due
to climate change and responses to those threats, adopting a more
threat-specific approach based on the best scientific and commercial
data available for each respective threat. For example, because the
climate projections in the Intergovernmental Panel on Climate Change's
(IPCC's) Fourth Assessment Report (AR4; IPCC, 2007) extend through the
end of the century (and we note the IPCC's Fifth Assessment Report
(AR5), due in 2014,
[[Page 41373]]
will extend even farther into the future), our updated analysis of
ribbon seals used the same models to assess impacts from climate change
through 2100, which is consistent with the time horizon used in our
recent examination of climate change effects for spotted, ringed, and
bearded seals. We continue to recognize that the farther into the
future the analysis extends, the greater the inherent uncertainty, and
we incorporated that limitation into our assessment of the threats and
the species' response. Not all potential threats to ribbon seals are
climate related, and therefore not all can be regarded as foreseeable
through the end of the 21st century. For example, evidence of
morbillivirus (phocine distemper) exposure in sea otters has recently
been reported from Alaska (Goldstein et al., 2009). Thus, distemper may
be considered a threat to ribbon seals, but the time frame of
foreseeability of an inherently episodic and novel threat is difficult
or impossible to establish. Similarly, factors that influence the
magnitude and foreseeability of threats from oil and gas industry
activities are difficult to predict beyond a few decades into the
future because of dynamic and changing trends in the global oil and gas
industry. These are only two examples of many potential threats without
clear horizons of foreseeability. Therefore, although it is intuitive
that foreseeability varies among threats facing ribbon seals, it is
impractical to explicitly specify separate horizons of foreseeability
for some of them (i.e., there is no consensus among BRT members, let
alone a broader community of scientists).
Faced with the challenge of applying the ``foreseeable future''
terminology of the ESA to a comprehensive scientific assessment of
extinction risk, the BRT opted to evaluate threats and demographic
risks on two time frames within the period defined by the horizon of
foreseeability for the threats of primary concern, namely those
stemming from greenhouse gas (GHG) emissions: (1) the period from now
to mid-century, corresponding to the time over which the IPCC considers
climate warming to be essentially determined by past and near-future
emissions; and (2) the period from now to the end of the century, a
period in which sustained warming is anticipated under all plausible
emissions scenarios, but the magnitude of that warming is more
uncertain. Consideration of threats (and demographic risks) within
these two time frames was intended to provide a sense of how the BRT's
judgment of all the threats and the level of certainty about those
threats may vary over the period of foreseeability for climate-related
threats. We agree with this threat-specific approach, which creates a
more robust analysis of the best scientific and commercial data
available. It is also consistent with the memorandum issued by the
Department of Interior, Office of the Solicitor, regarding the meaning
of the term ``foreseeable future'' (Opinion M-37021; January 16, 2009).
NMFS and FWS recently published a draft policy to clarify the
interpretation of the phrase ``significant portion of the range'' in
the ESA definitions of ``threatened'' and ``endangered'' (76 FR 76987;
December 9, 2011). The draft policy provides that: (1) If a species is
found to be endangered or threatened in only a significant portion of
its range, the entire species is listed as endangered or threatened,
respectively, and the ESA's protections apply across the species'
entire range; (2) a portion of the range of a species is
``significant'' if its contribution to the viability of the species is
so important that, without that portion, the species would be in danger
of extinction; (3) the range of a species is considered to be the
general geographical area within which that species can be found at the
time FWS or NMFS makes any particular status determination; and (4) if
the species is not endangered or threatened throughout all of its
range, but it is endangered or threatened within a significant portion
of its range, and the population in that significant portion is a valid
DPS, we will list the DPS rather than the entire taxonomic species or
subspecies.
The Services are currently reviewing public comment received on the
draft policy. While the Services' intent is to establish a legally
binding interpretation of the term ``significant portion of the
range,'' the draft policy does not have legal effect until such time as
it may be adopted as final policy. Here, we apply the principles of
this draft policy as non-binding guidance in evaluating whether to list
the ribbon seal under the ESA. If the policy changes in a material way,
we will revisit the determination and assess whether the final policy
would result in a different outcome.
Species Information
A thorough review of the taxonomy, life history, and ecology of the
ribbon seal is presented in the status review report (Boveng et al.,
2013). We provide a summary of this information below.
Description
The ribbon seal is a strikingly[hyphen]marked member of the family
Phocidae that primarily inhabits the Sea of Okhotsk and the Bering and
Chukchi seas. This species gets its common and specific (fasciata)
names from the distinctive band or ``ribbon'' pattern exhibited by
mature individuals, which consists of four light-colored ribbons on a
background of darker pelage. Ribbon seals are medium-sized when
compared to the other three species of ice-associated seals in the
North Pacific; they are larger than ringed seals, smaller than bearded
seals, and similar in size to spotted seals. Ribbon seals have
specialized physiological features that are likely adaptations for deep
diving and fast swimming, including the highest number and volume of
erythrocytes (red blood cells) and the highest blood hemoglobin
(oxygen-transport protein in red blood cells) of all seals, as well as
larger internal organs than those of other seals.
Distribution, Habitat Use, and Movements
The distribution of ribbon seals is restricted to the northern
North Pacific Ocean and adjoining sub-Arctic and Arctic seas, where
they occur most commonly in the Sea of Okhotsk and Bering Sea. Habitat
selection by ribbon seals is seasonally related to specific life
history events that can be broadly divided into two periods: (1) spring
and early summer (March-June) when whelping, nursing, breeding, and
molting all take place in association with sea ice on which the seals
haul out; and (2) mid-summer through fall and winter when ribbon seals
rarely haul out and are mostly not associated with ice.
In spring and early summer, ribbon seal habitat is closely
associated with the distribution and characteristics of seasonal sea
ice. Ribbon seals are strongly associated with sea ice during the
breeding season and not known to breed on shore (Burns, 1970; Burns,
1981). During this time, ribbon seals are concentrated in the ice front
or ``edge-zone'' of the seasonal pack ice, to as much as 150 km north
of the southern ice edge (Burns, 1970; Fay, 1974; Burns, 1981; Braham
et al., 1984; Lowry, 1985; Kelly, 1988). Shustov (1965a) observed that
ribbon seals were most abundant in the northern part of the ice front
and this north-south gradient has been observed in several other
studies as well. Shustov (1965a) also found that ribbon seal abundance
increased only with ice concentration and was unaffected by ice type,
shape, or form. This is in contrast to most studies which show that
ribbon seals generally prefer new, stable, white, clean, hummocky ice
floes, invariably with an even surface; it is rare to observe them on
dirty or
[[Page 41374]]
discolored floes, except when the ice begins to melt and haul-out
options are more limited (Heptner et al., 1976; Burns, 1981; Ray and
Hufford, 2006). Ribbon seals also seem to choose moderately thick ice
floes (Burns, 1970; Fay, 1974; Burns, 1981). These types of ice floes
are often located at the inner zone of the ice front and rarely occur
near shore, which may explain why ribbon seals are typically found on
ice floes far away from the coasts during the breeding season (Heptner
et al., 1976).
In most years, the Bering Sea pack ice expands to or near the
southern edge of the continental shelf. Most of this ice melts by early
summer. However, Burns (1969) described a zone of sea ice that remains
in the central Bering Sea until melting around mid-June. Satellite
imagery has verified the presence and persistence of this zone of ice
and has shown that it is located relatively close to the edge of the
continental shelf. Ribbon seals are numerous in this area, which is an
extremely productive region that likely provides rich foraging grounds
(Burns, 1981). Prey availability could strongly influence whelping
locations because females probably feed actively during the nursing
period (Lowry, 1985). In spring and early summer, ribbon seals are
usually found in areas where water depth does not exceed 200 m, and
they appear to prefer to haul out on ice that is near or over deeper
water, indicating their preference for the continental shelf slope
(Heptner et al., 1976). The seasonal dive-depth patterns of a small
sample of ribbon seals monitored by satellite telemetry are consistent
with a preference for feeding on the continental shelf slope (National
Marine Mammal Laboratory (NMML), unpublished data).
During May and June, ribbon seals spend much of the day hauled out
on ice floes while weaned pups develop self-sufficiency and adults
complete their molt. As the ice melts, seals become more concentrated,
with at least part of the Bering Sea population moving towards the
Bering Strait and the southern part of the Chukchi Sea. This suggests
that proximity to the shelf slope and its habitat characteristics
(e.g., water depth, available prey) become less important, at least
briefly around the molting period when feeding is likely reduced.
Although ribbon seals are strongly associated with sea ice during
the whelping, breeding, and molting periods, they do not remain so
after molting is complete. During summer, the ice melts completely in
the Sea of Okhotsk, and by the time the Bering Sea ice recedes north
through the Bering Strait, there are usually only a small number of
ribbon seals hauled out on the ice. Significant numbers of ribbon seals
are only seen again in winter when the sea ice reforms. The widespread
distribution and diving patterns of ribbon seals monitored by satellite
telemetry suggest that these seals are able to exploit many different
environments and can tolerate a wide range of habitat conditions in
mid-summer through winter.
Life History
The rates of survival and reproduction are not well known, but the
normal lifespan of a ribbon seal is probably 20 years, with a maximum
of perhaps 30 years. Ribbon seals become sexually mature at 1 to 5
years of age, probably depending on environmental conditions.
Whelping in the Bering Sea and northern Sea of Okhotsk occurs on
seasonal pack ice over a period of about 5-6 weeks, ranging from late
March to mid-May with a peak in early to mid-April (Tikhomirov, 1964;
Shustov, 1965b; Burns, 1981), perhaps with some annual variation
related to weather and ice conditions (Burns, 1981). The timing of
whelping in the southern Sea of Okhotsk and Tartar Straight is not
known, but may occur earlier, during March-April (Tikhomirov, 1966).
Pups are nursed for 3-4 weeks (Tikhomirov, 1968; Burns, 1981), during
which time mothers continue to feed, sometimes leaving their pups
unattended on the ice while diving. Most pups are weaned by mid-May,
which occurs when the mother abandons the pup (Tikhomirov, 1964).
Breeding occurs shortly after weaning.
Ribbon seals molt their coat of hair annually between late March
and July, with the timing of an individual's molt depending upon its
age and reproductive status (Burns, 1981). Sexually mature seals begin
molting around the time of mating, and younger seals begin molting
earlier.
Feeding Habits
The year-round food habits of ribbon seals are not well known, in
part because almost all information about ribbon seal diet is from the
months of February through July, and particularly March through June.
Ribbon seals primarily consume pelagic (open ocean) and nektobenthic
(swim near the seafloor) prey, including demersal (dwell near the
seafloor) fishes, squids, and octopuses. Walleye pollock (Theragra
chalcogramma) is a primary prey item, at least during spring, in both
the Bering Sea and the Sea of Okhotsk. Other fish prey species found in
multiple studies were Arctic cod (Boreogadus saida), Pacific cod (Gadus
macrocephalus), saffron cod (Eleginus gracilis), Pacific sand lance
(Ammodytes hexapterus), smooth lumpsucker (Aptocyclus ventricosus),
eelpouts, capelin (Mallotus villosus), and flatfish species. Several
species of both squid and octopus make up a significant part of ribbon
seal diets throughout their range. Some studies have also found that
crustaceans are an important part of the ribbon seal's diet. Several
studies indicate that pups and juveniles mainly feed on small
crustaceans and adults primarily consume fish and nektobenthos, like
walleye pollock, octopuses, and squids.
Current Abundance and Trends
Ribbon seal abundance estimates have been based on catch data from
sealing vessels, aerial surveys, and shipboard observations when seals
are hauled out on the ice to whelp and molt. Russian estimates of
Bering Sea abundance and trends were determined in the early 1960s from
commercial catch data. Aerial survey data were often inappropriately
extrapolated to the entire area based on densities and ice
concentration estimates without behavioral research to determine
factors affecting habitat selection. Very few details of the aerial
survey methods or data have been published, so it is difficult to judge
the reliability of the reported numbers. No suitable behavior data have
been available to correct for the proportion of seals in the water at
the time of surveys. Current research is just beginning to address
these limitations and no current and reliable abundance estimates have
been published.
Aerial surveys were conducted in portions or all of the ice-covered
Bering Sea east of the international date line by NMML in 2003
(Simpkins et al., 2003), 2007 (Cameron and Boveng, 2007; Moreland et
al., 2008; Ver Hoef et al., 2013), 2008, and 2012. A partial population
estimate of 61,100 ribbon seals in the eastern and central Bering Sea
(95 percent confidence interval: 35,200-189,300) was derived from the
surveys conducted in 2007 (Ver Hoef et al., 2013). Using restrictive
assumptions, the BRT scaled this number according to distributions of
ribbon seal breeding areas in 1987 (Fedoseev et al., 1988), to produce
total Bering Sea estimates ranging from 121,000 to 235,000. Similar
scaling based on a range-wide distribution presented by Fedoseev (1973)
produced Bering Sea, Sea of Okhotsk, and total-range estimates of
143,000, 124,000, and 267,000, respectively. Based on
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application of the 95 percent confidence interval reported by Ver Hoef
et al. (2013) to the scaled range-wide estimate of 267,000 animals, the
total range-wide abundance estimate could be as low as 154,000 or as
high as 827,000. Aerial surveys conducted during the spring of 2012 and
2013 in the Bering Sea and Sea of Okhotsk included many sightings of
ribbon seals, and preliminary analyses suggest that abundance estimates
derived from these data will be higher than those obtained in the more
limited survey reported by Ver Hoef et al. (2013).
Within the scaled range-wide estimate of 267,000, the Sea of
Okhotsk component of about 124,000 is lower than all but one previous
estimate for that region, and dramatically lower than the most recent
estimates from Russian surveys during 1979-1990, which ranged from
410,000 to 630,000 (Fedoseev, 2000). This difference may reflect a
failure of assumptions rather than a population decline. The BRT's
estimate for the Sea of Okhotsk was derived from a recent density
estimate in the Bering Sea, scaled by a much generalized distribution
from the 1960s of seals in the Sea of Okhotsk. The density estimate for
the Bering Sea may simply not be applicable to the distribution, and
vice versa. Lacking details about the Russian survey methods that
produced the larger numbers, and lacking any data on abundance in
Russian waters more recent than 1990, the BRT opted to use the smaller
number for the Sea of Okhotsk.
The BRT concluded that the current population trend of ribbon seals
cannot be determined, but that strong upward or downward trends in the
recent past seem unlikely. High rates of sightings in recent surveys,
and reports from Alaska Native subsistence hunters (Quakenbush and
Sheffield, 2007) that indicate stable or rising numbers, suggest that
there has not been a recent dramatic decline.
Species Delineation
Under our DPS policy (61 FR 4722; February 7, 1996), two elements
are considered in a decision regarding the potential identification of
a DPS: (1) the discreteness of the population segment in relation to
the remainder of the species or subspecies to which if belongs; and (2)
the significance of the population segment to the species or subspecies
to which is belongs. If a population segment is discrete and
significant (i.e., it is a DPS) its evaluation for threatened or
endangered status will be based on the ESA's definitions of those terms
and a review of the factors enumerated in ESA section 4(a)(1).
A population segment of a vertebrate species may be considered
discrete if it satisfies either one of the following conditions: (1)
``It is markedly separated from other populations of the same taxon as
a consequence of physical, physiological, ecological, or behavioral
factors. Quantitative measures of genetic or morphological
discontinuity may provide evidence of this separation''; or (2) ``It is
delimited by international governmental boundaries within which
differences in control of exploitation, management of habitat,
conservation status, or regulatory mechanisms exist that are
significant in light of section 4(a)(1)(D)'' of the ESA.
With respect to discreteness criterion 1, the BRT concluded, and we
concur, that although there are two main breeding areas for ribbon
seals, one in the Sea of Okhotsk and one in the Bering Sea, there is
currently no evidence of discrete populations on which to base a
separation into DPSs (see Boveng et al., 2013 for additional details).
As noted above, under the DPS policy, discreteness of a DPS may also be
considered based on delimitation by international governmental
boundaries within which differences in control of exploitation,
management of habitat, conservation status, or regulatory mechanisms
exist that are notable in light of section 4(a)(1)(D) of the ESA.
Ribbon seals occur throughout a vast area of international waters and
waters under the jurisdiction of the United States, the Russian
Federation, and the State of Alaska. The primary breeding locations are
in the territorial seas and exclusive economic zones of the United
States and the Russian Federation. There are differences between the
United States and the Russian Federation in the control of
exploitation, management of habitat, and regulatory mechanisms that
influence ribbon seal conservation status. For example, as noted in the
threats assessment below, and discussed in more detail in the status
review report, measures to control exploitation of ribbons seals appear
to be substantially different between the two nations. While commercial
hunting for ribbon seals is not allowed in the United States, such
harvests are permitted by the Russian Federation. Regulations which
govern commercial harvest of ice seals in Russia are over 20 years old
and quotas on ribbon seals in Russian waters would allow large
harvests. It is thus unclear what regulatory mechanisms are currently
in place to ensure that potential commercial harvests remain within
sustainable levels. Still, current commercial harvest levels remain low
because of poor economic viability, and unless efforts to develop new
uses and markets for seal products are successful, commercial harvest
of ribbon seals is unlikely to increase in the near future. As
discussed above, downward trends in ribbon seal population abundance in
the recent past seem unlikely, which suggests that the differences in
management between the United States and the Russian Federation are not
significant, and the potential for this to change is uncertain. We find
that the differences in management do not rise to a level that provides
a sufficient basis to justify the use of international boundaries to
satisfy the discreteness criterion of our DPS Policy (i.e., we found
that inadequacy of existing regulatory mechanisms does not pose a
significant threat to the persistence of the ribbon seal and is not
likely to do so in the foreseeable future). In addition, we note that
the maritime boundary between the United States and the Russian
Federation does not specifically delimit the Sea of Okhotsk breeding
area. Rather, this international boundary divides the eastern and
central Bering Sea portion of the ribbon seal range (i.e., U.S.) from
the western Bering Sea and Sea of Okhotsk (i.e., Russian) portion. In
other words, delimitation by international governmental boundaries
would place the division in the Bering Sea, where the distribution of
ribbon seal breeding areas appears to be continuous and where ribbon
seals move routinely without regard to the maritime boundary. We
therefore conclude that there are no population segments that satisfy
the discreteness criteria of our DPS Policy. Since there are no
discrete population segments, we cannot take the next step of
determining whether any discrete population segment is significant to
the taxon to which it belongs.
Summary of Factors Affecting the Ribbon Seal
The following sections discuss threats to the ribbon seal under
each of the five factors specified in Section 4(a)(1) of the ESA and 50
CFR 424. The reader is also directed to section 4.2 of the status
review report (Boveng et al., 2013) for a more detailed discussion of
the factors affecting the ribbon seal. As discussed above, the data on
ribbon seal abundance and trends in abundance are very imprecise, and
there is little basis for quantitatively linking projected
environmental conditions or other factors to ribbon seal survival or
reproduction. Our risk assessment therefore primarily evaluated
important habitat features and was based upon the
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best available scientific and commercial data and the expert opinion of
the BRT members.
A structured approach was used to elicit the BRT members' judgment
about the significance of the threats facing ribbon seals (excluding
Factor D). The primary threats identified were grouped by each ESA
Section 4(a)(1) factor, and each individual threat was scored for its
significance, in two components (each on a 5-level scale): (1) extent
(portion of the population that would experience reduced survival or
reproductive success if the threat condition were to occur), and (2)
likelihood of occurrence within a specified time period in the
foreseeable future. For many threats, such as oil spills, there are a
broad range of plausible extents with little or no consensus about what
scenarios are most plausible. Consequently, for such threats, the
process of judging significance was often an iterative one in which
extent was not always judged before likelihood, and vice-versa. Because
of potential differences in the strengths of the threats between the
Bering Sea and Sea of Okhotsk, the BRT assigned scores separately for
these two portions of the ribbon seal's range.
Each BRT member assigned extent and likelihood scores for each
threat for the time period of now to mid-century, and now to the year
2100. Consideration of threats within these two time frames was
intended to provide a sense of how the BRT's judgment of all the
threats and the level of certainty about those threats may vary over
the period of foreseeability for climate-related threats. For the
period now to 2100, a threat score was also computed for each threat by
multiplying the extent score by the likelihood score The range of these
threat scores was divided into significance categories of ``low'' (1-
4), ``moderate'' (5-10), ``high'' (11-15), ``very high'' (16-20), and
``extreme'' (21-25). Using the same scale as for the threat scores,
each BRT member also considered the individual threat scores in
assigning an overall score for each ESA section 4(a)(1) factor
(excluding Factor D). These overall factor scores reflect the BRT's
judgment about the significance of each factor as a whole, including
cumulative impacts. The average score and range of scores among BRT
members are reported in the status review report. In this listing
determination we summarize the average threat and overall factor
scores. Additional details are contained in the status review report.
A. Present or Threatened Destruction, Modification, or Curtailment of
the Species' Habitat or Range
The main concerns about the conservation status of the ribbon seal
stem from the likelihood that its sea ice habitat has been modified by
the warming climate and, more so, that the scientific consensus
projections are for continued and perhaps accelerated warming in the
foreseeable future which could make large areas of habitat less
suitable for ribbon seals. A second concern, related by the common
driver of carbon dioxide (CO2) emissions, is the
modification of habitat by ocean acidification, which may alter prey
populations and other important aspects of the marine environment. A
reliable assessment of the future conservation status of ribbon seals,
therefore, requires a focus on the observed and projected changes in
sea ice, ocean temperature, ocean pH (acidity), and associated changes
in ribbon seal prey species. The threats associated with impacts of the
warming climate on the habitat of ribbon seals, to the extent that they
may pose risks to these seals, are expected to manifest throughout the
current breeding and molting range (for sea ice related threats) or
throughout the entire range (for ocean warming and acidification) of
the ribbon seal.
Effects of Climate Change on Annual Formation of the Ribbon Seal's Sea
Ice Habitat
Unlike the Arctic Ocean, where some sea ice is present year round
(i.e., multi-year ice), the ice in the Bering Sea and Sea of Okhotsk is
seasonal and forms every winter as first-year ice. The main
thermodynamic physical influence at high latitudes is the cold and
darkness that occurs in winter. Despite the recent dramatic reductions
in Arctic Ocean ice extent during summer, the sea ice in the northern
Bering Sea and Sea of Okhotsk is expected to continue forming annually
in winter for the foreseeable future, with large interannual variations
in sea ice extent and duration. The future central Arctic will also
continue to be an ice[hyphen]covered sea in winter, but will contain
more first[hyphen]year sea ice than multi[hyphen]year ice.
Ice extent in marginal seas such as the Bering Sea is characterized
not by summer minima, since these seas have been ice[hyphen]free in
summer throughout recorded history, but rather by winter maxima.
Freezing conditions in the northern Bering Sea persist from December
through April. Mean monthly maximum temperatures at Nome, Alaska are -
3[deg]C or below for all months November through April. Freezing rather
than thawing should still predominate in these months even if a
hypothesized ~3[deg]C global warming signal is realized. The result is
that the seasonal formation of sea ice in the northern Bering Sea and
Sea of Okhotsk is substantially decoupled from the summer ice extent in
the Arctic Ocean, and is expected to continue annually through the
foreseeable future, along with large interannual variations in extent
and duration of persistence.
IPCC Model Projections
Comprehensive Atmosphere-Ocean General Circulation Models (AOGCMs)
are the major objective tools that scientists use to understand the
complex interaction of processes that determine future climate change.
The IPCC used the simulations from about two dozen AOGCMs developed by
17 international modeling centers as the basis for the AR4 (IPCC,
2007). The analysis and synthesis of information presented by the IPCC
in its AR4 represents the scientific consensus view on the causes and
future of climate change. The AR4 used a range of future GHG emissions
produced under six illustrative ``marker'' scenarios from the Special
Report on Emissions Scenarios (SRES) (IPCC, 2000) to project plausible
outcomes under clearly-stated assumptions about socio-economic factors
that will influence the emissions. Conditional on each scenario, the
best estimate and likely range of emissions were projected through the
end of the 21st century. It is important to note that these scenarios
do not contain explicit assumptions about the implementation of
agreements or protocols on emission limits beyond current mitigation
policies and related sustainable development practices.
More recent climate model projection experiments are in progress in
preparation for publication of the IPCC's Fifth Assessment Report (AR5)
in 2014. However, the AR5 is not yet available. Therefore, the BRT used
the modeling results from the AR4 in the status review. Knutti and
Sedlacek (2012) found that projected global temperature change from the
new models that will be used in the AR5 is remarkably similar to that
from those models used in the AR4 after accounting for the different
underlying emissions scenarios, and the spatial patterns of temperature
and precipitation change were also very consistent. The AOGCMs provide
reliable projections because they are built on well-known dynamical and
physical principles, and they simulate quite well many large scale
aspects of present-day conditions. However, the coarse resolution of
most
[[Page 41377]]
current climate models dictates careful application on small scales in
heterogeneous regions, such as along coastlines.
There are three main contributors to divergence in AOGCM climate
projections: large natural variations, across-model differences, and
the range in emissions scenarios. The first of these, variability from
natural variation, can be incorporated by averaging the projections
over decades, or, preferably, by forming ensemble averages from several
runs of the same model. The second source of variation, across-model
differences, results from differences among models in factors such as
spatial resolution. This variation can be addressed and mitigated in
part by using the ensemble means from multiple models.
The third source of variation arises from the range in plausible
emissions scenarios. Conditions such as surface air temperature and sea
ice area are linked in the IPCC climate models to GHG emissions by the
physics of radiation processes. When CO2 is added to the
atmosphere, it has a long residence time and is only slowly removed by
ocean absorption and other processes. Based on IPCC AR4 climate models,
expected increases in global warming--defined as the change in global
mean surface air temperature (SAT)--by the year 2100 depend strongly on
the assumed emissions of CO2 and other GHGs, versus natural
variations across-model differences (IPCC, 2007). By contrast, global
warming projected out to about 2040-2050 will be primarily due to
emissions that have already occurred and those that will occur over the
next decade. Thus, conditions projected to mid-century are less
sensitive to assumed future emission scenarios than are longer-term
projections to the end of the century. Uncertainty in the amount of
warming out to mid-century is primarily a function of model-to-model
differences in the way that the physical processes are incorporated,
and this uncertainty can be addressed in predicting ecological
responses by incorporating the range in projections from different
models. Because the current consensus is to treat all SRES emissions
scenarios as equally likely, one option for representing the full range
of variability in potential outcomes would be to project from any model
under all of the six ``marker'' scenarios. This can be impractical in
many situations, so the typical procedure for projecting impacts is to
use an intermediate scenario to predict trends, or one intermediate and
one extreme scenario to represent a significant range of variability.
There is no universal method for combining AOGCMs for climate
projections, and there is no one best model. The approach taken by the
BRT for selecting the models used to project future sea ice in the
status review report is summarized below.
Data and Analytical Methods
Many of the anticipated effects of GHG emissions have been
projected through the end of the 21st century, subject to certain
inputs and assumptions, and these projections currently form the most
widely accepted version of the best available data about future
environmental conditions. In our risk assessment for ribbon seals, we
therefore considered climate model projections through the end of the
21st century to analyze the threats stemming from climate change.
The IPCC model simulations used in the BRT analyses were obtained
from the Program for Climate Model Diagnosis and Intercomparison
(PCMDI) on-line (at http://www-pcmdi.llnl.gov/). Wang and Overland
(2009) identified a subgroup of six of these models that met
performance criteria for reasonably reproducing the observed magnitude
of the seasonal cycle of Northern Hemisphere sea ice extent. Climate
models generally perform better on continental or larger scales, but
because habitat changes are not uniform throughout the hemisphere,
using similar performance criteria, the BRT further evaluated each of
these six IPCC models independently on their performance at reproducing
the observed seasonal cycle of sea ice extent during April and May in
each of four regions--the Sea of Okhotsk, western Bering Sea, eastern
Bering Sea, and Chukchi Sea.
All six of the models met the performance criteria for sea ice in
the Chukchi Sea and four of the six models met the criteria for the
eastern Bering Sea. Only one of the six models was in reasonable
agreement with observations for the western Bering Sea; this single
model was therefore used to project sea ice in this region with caveats
about the reliability as noted below. Due to model deficiencies and the
small size of the Sea of Okhotsk region relative to the spatial
resolution of the climate models, none of the models met the
performance criteria for this region. Instead, for the Sea of Okhotsk,
comparison of SAT projections with current climate conditions was
considered. Thirteen models, which were selected based on their ability
to represent the climate of the North Pacific (Overland and Wang,
2007), were used to project future SATs in the Sea of Okhotsk. Whether
future monthly mean SATs are above or below the freezing point of sea
water provides a reasonable indicator of the presence or absence of sea
ice. Projections of SATs for the Sea of Okhotsk were considered under
both a medium and a high emissions scenario; similarly, model output
under both of these emissions scenarios was considered for the other
three regions.
While our inferences about future regional ice conditions are based
upon the best available scientific and commercial data, we recognize
that there are uncertainties associated with predictions based on
hemispheric projections or indirect means. We also note that judging
the timing of onset of potential impacts to ribbons seals is
complicated by the coarse resolution of the IPCC models. For example,
in June 2008 the NOAA ship Oscar Dyson encountered a field of ice with
numerous ribbon and spotted seals near St. Matthew Island in an area
where no ice was visible on the relatively high resolution (12.5 km)
satellite images of sea ice for that day. Nevertheless, NMFS concluded
that the models reflect reasonable assumptions regarding habitat
alterations to be faced by ribbon seals in the foreseeable future.
Regional Sea Ice Projections
The projections indicate that within this century there will be no
significant ice reductions in the Chukchi Sea in winter through early
spring (January to May). A downward trend in ice extent is evident in
the Chukchi Sea in June toward the end of the century, by which time
the difference between the emissions scenarios becomes a major
contributor to the trends. Interannual variability of the model
projections is larger in the Chukchi Sea after mid-century. In the
eastern Bering Sea, a gradual downward trend in the sea ice extent is
apparent over the century in March through May, albeit with a large
degree of interannual variability. The average sea ice extent in the
eastern Bering Sea during these months is projected to be at 58 percent
of the present day value by 2050, and at 37 percent of the present day
value by 2075. As discussed above, ice projections were only available
for the western Bering Sea from a single model, so the results must be
interpreted in the context of possibly large bias and lack of model-to-
model variation. Compared with observations, this model overestimated
sea ice extent in both March and April, but performed reasonably well
for May and June. The model projected a rapid decline in sea ice extent
in the western Bering Sea over the first half of this century in
[[Page 41378]]
March and April, then relative stability to the end of the century. The
model projected that the western Bering Sea will continue to have ice
in March and April through nearly the end of the 21st century; however,
the average sea ice extent in the latter half of this century in these
months is projected to be approximately 25 percent of the present-day
extent. The projection for May indicates that there will commonly be
years when the western Bering Sea will have little or no ice beyond
mid-century. Mapped projections of sea ice concentrations in the two
Bering Sea regions indicate that by mid-century and beyond, the Bering
Sea can be expected to have essentially no ice during May in some
years, and by 2090 May sea ice can be expected only in the northern
Bering Sea.
As noted above, none of the IPCC models performed satisfactorily at
projecting ice for the Sea of Okhotsk, and so projected SATs were
considered relative to current climate conditions as a proxy to predict
sea ice extent and duration. The Sea of Okhotsk lies to the southwest
of the Bering Sea and thus can be expected to have earlier radiative
heating in spring. However, this region is dominated by cold
continental air masses and offshore flow for much of the winter and
spring. Therefore, the present seasonal cycle of the formation of
first-year sea ice during winter is expected to continue annually in
the foreseeable future. Based on the temperature proxies, a
continuation of sea ice formation or presence is expected for March
through the end of this century, though the ice may be limited to the
northern portion of this region in most years after mid-century.
Conditions for sea ice in April are likely to be limited to the far
northern reaches of the Sea of Okhotsk, or non-existent if the
projected warming occurs by 2100. Recent climate data indicate that
during May, sea ice has warmed to the melting point throughout the Sea
of Okhotsk region.
In summary, within the ribbon seal's range large areas of annual
sea ice are expected to form and persist through April in most years
throughout this century. However, in the Sea of Okhotsk conditions for
sea ice in April are likely to be limited to the far northern reaches
or non-existent if the projected warming occurs by 2100. In May, ice is
projected to continue to occur in the Bering Sea in most years through
mid-century, but in the latter half of the century many years are
expected to have little or no ice. Sea ice extent in June is expected
to be highly variable through mid-century, as it has been in the past,
but the models project essentially no ice in the Bering Sea in June
during the latter half of the century.
Potential Impacts of Changes in Sea Ice on Ribbon Seals
In association with a long[hyphen]term warming trend, there will
likely be changes in the frequency of years with extensive ice, the
quality of ice, and the duration of its persistence that may impact the
amount of suitable habitat in the geographic areas that ribbon seals
have preferred in the past. An assessment of the risks posed by these
changes must consider the ribbon seal life[hyphen]history functions
associated with sea ice and the potential effects on the vital rates of
reproduction and survival. As discussed above, the sea ice regimes in
the Bering Sea and Sea of Okhotsk will continue to be subject to large
interannual variations in extent and seasonal duration, as they have
been throughout recorded history. While there may be more frequent
years in which sea ice coverage is reduced, the late[hyphen]March to
early[hyphen]May period in which the peak of ribbon seal reproduction
occurs will continue to have substantial ice for the foreseeable
future. Still, there will likely be more frequent years in which the
ice is confined to the northern regions of the observed breeding range.
In contrast to harp seals (Pagophilus groenlandicus), which are
their closest relatives, ribbon seals appear much less closely tied to
traditional geographic locations for important life history functions
such as whelping and molting. In years of low ice it is likely that
ribbon seals will adjust, at least in part, by shifting their breeding
locations in response to the position of the ice edge, as they have
likely done in the past in response to interannual variability (e.g.,
Fedoseev, 1973; Braham et al., 1984; Fedoseev et al., 1988), at least
in the Bering Sea (this may not be possible in the Sea of Okhotsk,
where there is no northern access to higher-latitude ice-covered seas
because the sea is bounded to the north by land). For example,
observations indicate that extreme dispersal of ribbon seals within
their effective range is associated with years of unusual ice
conditions. The formation of extensive ice in the Bering Sea and Sea of
Okhotsk has been found to result in the occurrence of large numbers of
these seals farther south than they normally occur; the reverse is also
true (Burns, 1981).
There has not been, however, any study that would verify whether
vital rates of reproduction or survival have been affected by these
interannual variations in ice extent and breeding. Whelping, nursing of
pups, and maturation of weaned pups could conceivably be impacted in
years when the ice does not extend as far south as it has typically in
the past, because the breeding areas would be farther from the
continental shelf break, a zone that seems to be a preferred foraging
area during spring. If these conditions occur more frequently, as is
anticipated from projections of future climate and sea ice conditions,
reproduction and survival of young would likely be impacted. Lacking
relevant data, the most conservative approach is to assume that the
population has been at equilibrium with respect to conditions in the
past, and that a change such as more frequent breeding farther from
preferred foraging habitats will have some impact on vital rates. Even
given the uncertainties, we conclude that the anticipated increase in
frequency of years with low ice extent in April and May is likely to
have some impact on recruitment. The mechanisms for depressed
recruitment from increased frequency of years with less ice could
include reduced nutrition during the nursing period caused by mothers
unable to reach preferred shelf-break foraging areas; pup mortality
caused by more frequent failures for mothers to reunite with pups left
on the ice during foraging trips; and mortality or reduced condition of
maturing weaned pups caused by reduced availability of suitable ice for
hauling out.
As discussed above, ribbon seals have an apparent affinity for
stable, clean, moderate[hyphen]sized ice floes that are slightly, but
not deeply interior to the pack ice edge. Ice of this type is likely to
occur annually in the Bering Sea and Sea of Okhotsk through the middle
of this century, but it may more frequently be confined to smaller
areas or areas farther north than in the past. It is more difficult to
determine whether this type of ice will be relatively more or less
available as the amount of ice declines as projected through the latter
half of the century. The availability of moderately-thick, stable ice
floes could potentially influence ribbon seal demography, particularly
in May, via survival rates of weaned pups. Pups spend a great deal of
time on the ice during a transition period of 2 to 3 weeks following
weaning, presumably developing their capabilities for self-sufficient
foraging (Burns, 1981). However, they also enter the water frequently
during this period, and therefore may not be particularly sensitive to
modest reductions in ice coverage or quality. Thus, although they are
likely dependent on ice, weaned pups may not require ice floes that can
[[Page 41379]]
persist for weeks to meet their basic haul-out needs. They may,
however, be relatively limited in their capability to respond to
rapidly deteriorating ice fields by relocating over large distances, a
factor that could occur more frequently in the foreseeable future.
Subadult ribbon seals, which molt earlier than adults during March
to mid[hyphen]May, and which are not constrained by habitat
requirements for whelping and breeding, may be the least sensitive to
the availability and quality of sea ice. For example, in 2007, NMFS
research cruises in the Bering Sea encountered subadult ribbon seals in
approximately the expected age class proportions. The obvious presence
of seals in the subadult age class indicated that catastrophic losses
had not occurred in the ribbon seal cohorts produced during the warm
years of 2001-2005.
Adult ribbon seals, which are the last to molt, might be expected
to be the most sensitive to timing of the ice melt. Tikhomirov (1964)
suggested that molting ribbon seals rarely enter the water and that
stable ice is critical during this period. The pelage molt of phocid
seals is generally thought to be facilitated or enhanced by elevated
skin temperatures that can be achieved when hauled out versus in the
water (Feltz and Fay, 1966). For example, it has been suggested that
the harbor seal (Phoca vitulina, a small phocid, similar in size and
body composition to a ribbon seal), could not complete its molt
entirely in the water at temperatures that the species would normally
encounter in the wild (Boily, 1995). Analysis of haul[hyphen]out
records (section 2.6 of the status review report) indicate that
individual adult ribbon seals haul out almost continuously for a period
of weeks, mostly during mid[hyphen]May to late June, corresponding to
the observed peak in molting. Sea ice coverage in June is expected to
be low or absent more frequently in the foreseeable future. The
implications of a loss of access to a haul[hyphen]out substrate during
this period are unknown, but they may include energetic costs, reduced
fertility, increased susceptibility to skin disorders and pathogens,
and possibly increased exposure to any risks from which the hair
normally protects a seal (e.g., abrasion from crawling over snow and
ice). Many reports of ribbon seals out of their normal range or habitat
have been associated with some pelage abnormalities, usually consistent
with a disrupted or delayed molt. However, adult ribbon seals may also
be less constrained to a specific geographic area or region of the ice
pack once breeding is complete, around the onset of the adult molt
(Boveng et al., 2007). They may therefore be capable of considerable
shifts in distribution to ensure contact with suitable ice through the
molt period, especially in the Bering Sea where there is access through
the Bering Strait to the Chukchi Sea, where ice is expected to persist
more frequently in June. The ultimate effect of decreased availability
of stable platforms for adults to complete their molt out of the water
on adult survival rate is currently difficult or impossible to model.
The impacts discussed above on ribbon seal survival and
reproduction in years of low ice extent, poor ice quality, or early
melting are all of a sort that would not necessarily be significant in
any one year; a year of low ice extent seems unlikely to cause
widespread mortality through disruption of the adult molt, or increased
energetic costs for pups developing their foraging capabilities.
Rather, the overall strength of the impacts is likely a function of the
frequency of years in which they are anticipated to occur, and the
proportion of the population's range over which they would occur. Also,
the effects on different age classes might be expected to be
correlated, though not always in concert, because they involve ice
characteristics at different times in the breeding[hyphen]molting
period; low ice extent during breeding may not always be accompanied by
early melting, and vice versa. As above, in the assessment of impacts
on reproduction, we conclude that the anticipated increase in frequency
of years with low ice extent in April, May, and June is likely to have
an impact on survival rates.
The extent to which ribbon seals might adapt to more frequent years
with early ice melt by shifting the timing of reproduction and molting
is unknown. There are many examples in the scientific literature of
shifts in the timing of reproduction by pinnipeds and terrestrial
mammals in response to body condition and food availability. In most of
these cases, sub[hyphen]optimal conditions led to later reproduction,
which would not likely be beneficial to ribbon seals as a response to
earlier spring ice melt. Over the longer term (i.e., beyond the
foreseeable future) a shift to an earlier mean melt date may provide
selection pressure for an evolutionary response over many generations
toward earlier reproduction.
In summary, more frequent future years of reduced spring ice extent
or ice quality could result in reduced vital rates of ribbon seal
reproduction and survival. These potential impacts are premised on the
assumption of a population at equilibrium with conditions in the recent
(cooler) past and the related possibility that changes such as
displacement of breeding locations or reduced availability of preferred
ice types will have some energetic costs that will ultimately be
reflected in vital rates. The age of maturation for ribbon seal females
has been very low and pregnancy rates have been high in the recent past
(Quakenbush and Citta, 2008), implying that foraging conditions have
been favorable, a scenario more likely to reflect population growth
rather than equilibrium; if so, there may be some capacity to withstand
a reduction in vital rates without incurring an actual population
decline. In the absence of relevant data, it is not feasible to
estimate quantitatively the magnitude of the anticipated impacts. The
significance of demographic risks to the persistence of ribbon seals
within the foreseeable future is assessed qualitatively below (see
Demographic Risks Assessment).
The threats associated with decreases in sea ice habitat that were
judged by the BRT to be of high significance include reductions in sea
ice habitat suitable for molting in both the Bering Sea and the Sea of
Okhotsk; and reductions in sea ice habitat suitable for whelping and
nursing, pup maturation, and mating in the Sea of Okhotsk. Reductions
in sea ice habitat suitable for whelping and nursing, pup maturation,
and mating in the Bering Sea were judged by the BRT to be of moderate
significance. We concur with the BRT's assessment.
Impacts on Ribbon Seals Related to Changes in Ocean Conditions
Ocean acidification is an ongoing process whereby chemical
reactions occur that lower seawater pH and carbonate saturation due to
CO2 absorption by the ocean. Ocean acidification is likely
to affect the ecosystem structure in the ribbon seals' habitats in the
foreseeable future. The exact nature of these impacts cannot be
predicted, and some likely will amplify more than others. As discussed
above, ribbon seals eat a variety of fishes, squids, octopuses, and
crustaceans. In addition to interfering with calcification of organisms
at lower trophic levels, changes in ocean chemistry can have direct
effects on the physiology of marine invertebrates and fish. Among
invertebrates, squid are expected to be particularly sensitive to
increases in CO2. These ecosystem responses may have very
long lags as they propagate through trophic webs.
Although the ribbon seal's varied diet would appear to confer some
resilience
[[Page 41380]]
to shifts in prey availability, major disruptions in the amount of
productivity reaching pelagic, upper trophic species would be expected
to have demographic impacts. Survival of juvenile ribbon seals would be
expected to be the most sensitive, as their diet is narrower and more
skewed toward invertebrates. Sufficiently large ecosystem shifts that
persist more than a few years could also impact adult survival and
reproductive rates. The range of potential ecological scenarios,
however, is extremely complex and may even include some that could be
ameliorative or beneficial to ribbon seals. The vast preponderance of
ocean acidification impacts that have been identified, however, seem
negative for ribbon seal prey. In the absence of compelling evidence
for specific positive effects, the net effect of ocean acidification on
ribbon seals is expected to be negative. The threat posed to ribbon
seals from decreases in prey density and/or availability due to ocean
acidification was judged by the BRT to be of moderate significance in
both the Bering Sea and Sea of Okhotsk, and we agree with this
assessment.
Changes in ribbon seal prey, anticipated in response to habitat
changes resulting from ocean warming and loss of sea ice, have the
potential for negative impacts, but these impacts are not well
understood. Some changes already documented in the Bering Sea and the
North Atlantic Ocean are of a nature that could be ameliorative or
beneficial to ribbon seals. For example, warming and decrease in ice
extent could increase pelagic productivity in favor of pelagic foraging
by ribbon seals. Such ecosystem responses may have very long lags as
they propagate through trophic webs. The apparent flexibility in ribbon
seal foraging locations and habits may make the threats posed from
changes in prey due to ocean warming and loss of ice of lower concern
than more direct impacts from changes in sea ice. The BRT judged the
threats posed to ribbon seals from decreases in prey density and/or
availability due to changes in ice cover and ocean warming to be of
moderate significance in both the Bering Sea and the Sea of Okhotsk,
and we agree with this assessment.
Summary of Factor A
The BRT judged the threats to ribbon seal persistence from
destruction or modification of habitat to be of greater significance
than the threats posed from all other factors. Overall, the BRT judged
the threats posed under Factor A to be of high significance in the
Bering Sea and of very high significance in the Sea of Okhotsk. The BRT
concluded that although it is impossible to project the trajectory of
ribbon seal abundance with any certainty, it is likely that the
combined effects of diminished sea ice habitat and disrupted prey
communities will reduce ribbon seals' vital rates of survival and
reproduction gradually throughout the foreseeable future. We agree with
the BRT's findings. However, as discussed below, our analysis did not
indicate these anticipated impacts on ribbon seal vital rates render
the species likely to become an endangered species within the
foreseeable future (threatened). Relevant considerations supporting
this conclusion include: (1) There is evidence from some recent years
with unusual ice conditions that ribbon seals may compensate for
changes in sea ice, as least in part, by moving to areas with better
ice, at least in the Bering Sea; (2) ribbon seals are known to have a
diet that is ecologically and trophically diverse and they are able to
forage over a wide range of ocean depths, which should enhance
resilience to climate-related changes in prey communities; and (3)
individual ribbon seals have the capability to undertake large seasonal
movements and shifts between pelagic and pack ice habitats, which may
mitigate some anticipated impacts of anthropogenic climate change. The
demographic risks to the persistence of ribbon seals within the
foreseeable future are considered further below (see Demographic Risks
Assessment).
B. Overutilization for Commercial, Subsistence, Recreational,
Scientific, or Educational Purposes
While commercial hunting for ribbon seals is not allowed in the
United States, such harvests are permitted by the Russian Federation.
Commercial harvests by Russian sealers have at times been high enough
to cause significant reductions in abundance and catch-
per[hyphen]unit[hyphen]effort. The population apparently rebounded from
a period of high harvest in the 1960s. Substantial but lower numbers
were harvested for a few years in the early 1990s. Although Russian
government quotas were recently put in place that would allow large
harvests (~18,000 annually), the actual takes are low because of poor
economic viability. There is some effort in Russia to develop new uses
and markets for seal products, but unless this effort is successful,
the harvest is unlikely to increase in the near future. The numbers of
ribbon seals harvested for subsistence use by indigenous hunters in
Russia and Alaska are considered insignificant by most researchers,
primarily due to the difficulty of accessing the seals in far offshore
ice. Subsistence harvest levels have been low historically in Russia,
and the current subsistence harvest is not thought to be a threat to
ribbon seals there. Although estimates of subsistence harvest in Alaska
are varied, all are low and sustainable relative to the population
size. Subsistence harvest levels could potentially increase in the
future if ribbon seals are forced to use a reduced and more northerly
ice field, which could put them in closer proximity to Alaska Native
communities near the Bering Strait. Changes in subsistence or
commercial takes cannot be predicted with any certainty at this time.
Scientific and educational utilization of ribbon seals is currently at
very low levels and is not projected to increase to significant threat
levels in the foreseeable future. Overall, the significance of the
threats posed to ribbon seal persistence from overutilization were
judged by the BRT to be low in both the Bering Sea and the Sea of
Okhotsk, and we concur with this finding.
C. Diseases, Parasites, and Predation
A variety of pathogens (or antibodies), diseases, helminthes,
cestodes, and nematodes have been found in ribbon seals. The prevalence
of these agents is not unusual among seals, but the population impact
is unknown. Beginning in July and August 2011, higher than normal
numbers of sick and dead ringed seals along the coast of the North
Slope of Alaska led to the declaration of an unusual mortality event
(UME). Most pinnipeds with UME symptoms were ringed seals from the
North Slope, but sick walruses (Odobenus rosmarus), spotted seals, and
bearded seals were also found on the North Slope and in the Bering
Strait region. Only one ribbon seal, a yearling, was reported with UME
symptoms. The cause of the UME is still unknown, but additional
bacterial and fungal testing and advanced molecular screening for
unknown viruses are being conducted in a continuing effort to determine
an explanation. There are a couple possibilities that may explain why
only one sick ribbon seal was found during this UME. Ribbon seals are
primarily pelagic and solitary during the summer and fall months when
most of the UME seals were found. Thus, they might not have become sick
in the same numbers as other ice seals because disease transmission
among individuals may be limited due to their solitary lifestyle.
However, it is also possible that many ribbon seals did become sick
during the UME, but because they are pelagic they may have died out at
sea and not stranded in areas where they could be
[[Page 41381]]
counted. There may be an increased risk of outbreaks of novel pathogens
or parasites as climate[hyphen]related shifts in species distributions
lead to new modes of transmission. For both the Bering Sea and the Sea
of Okhotsk, the BRT judged the potential threats to ribbon seals from
increased infection or disease to be of moderate significance, and from
an increase in parasites to be of low significance, and we agree with
these findings.
There is little or no direct evidence of significant predation on
ribbon seals, and they are not thought to be a primary prey of any
predators. Polar bears (Ursus maritimus) and killer whales (Orcinus
orca) may be the most likely opportunistic predators in the current sea
ice regime, but walruses and sharks could pose a potentially greater
risk if reduced sea ice conditions force these species into closer
proximity in the future. The BRT judged the significance of the threat
posed to ribbon seals from increased predation associated with changes
in sea ice cover to be low in both the Bering Sea and the Sea of
Okhotsk, and we agree with this assessment.
D. Inadequacy of Existing Regulatory Mechanisms
As noted above in the discussion of Factor A, a primary concern
about the conservation status of the ribbon seal stems from the
likelihood that its sea ice habitat has been modified by the warming
climate and, more so, that the scientific consensus projections are for
continued and perhaps accelerated warming in the foreseeable future
combined with modification of habitat by ocean acidification and
warming water temperatures. Current mechanisms do not effectively
regulate GHG emissions, which are contributing to global climate change
and associated modifications to ribbon seal habitat. The projections we
used to assess risks from GHG emissions were based on the assumption
that no new regulation will take place (the underlying IPCC emissions
scenarios were all ``non-mitigated'' scenarios). Therefore, the
inadequacy of mechanisms to regulate GHG emissions is already included
in our risk assessment, and contributes to the risks posed to ribbon
seals by these emissions.
We also note that regulations which govern commercial harvest of
ice seals in Russia are over 20 years old and we do not have good
information regarding whether regulatory mechanisms are in place to
ensure that potential commercial harvests in Russian waters are
conducted in a sustainable fashion. As noted above, currently there is
some effort in Russia to develop new uses and markets for seal
products, but unless this effort is successful, the harvest is unlikely
to increase in the near future. The BRT considered the threat posed to
ribbon seal persistence by commercial harvest to be low in both the
Bering Sea and the Sea of Okhotsk. We conclude that the data currently
available do not suggest that inadequacy of mechanisms to regulate
commercial harvest poses a significant threat to ribbon seals.
E. Other Natural or Manmade Factors Affecting the Species' Continued
Existence
Although some pollutants are elevated in ribbon seals, there is no
conspicuous evidence of toxicity or other significant impacts to the
species. Continued and expanded monitoring would be prudent to document
any trends in the contaminants of greatest concern.
Oil and gas exploration and development activities may include
drilling operations, pipeline construction and operation, seismic
surveys, and vessel and aircraft operations. The main issues for
evaluating the impacts of exploration and development activities on
ribbon seals are the effects of noise, physical disturbance, and
potential oil spills produced from these activities. Any negative
effects on ribbon seals from noise and disturbance associated with
development activities are likely to be minor and localized. Ribbon
seals are also highly dispersed during the summer open[hyphen]water
season, so the rate of interactions with seismic surveys would likely
be low, and, in any case, seals have not been shown to be significantly
impacted by oil and gas seismic surveys. The threat posed to ribbon
seals by oil spills will increase if offshore oil and gas development
and shipping activities increase across their range as predicted. The
potential impacts would be greatest during April-June when the seals
are relatively aggregated, and substantially lower during the remainder
of the year when they are dispersed in the open water throughout the
North Pacific Ocean, Sea of Okhotsk, and Bering and Chukchi seas.
Estimates from observed bycatch in commercial fisheries indicate
that less than 200 ribbon seals per year are taken, though mortalities
may be under[hyphen]reported in some fisheries. This level of estimated
bycatch of ribbon seals represents less than 0.1 percent of their
estimated population. Because there is little or no fishery activity
near the widely distributed low densities of ribbon seals when they are
associated with ice, and they are highly dispersed during the remainder
of the year, bycatch is unlikely to be a significant threat to ribbon
seal populations. For the same reason, competition from fisheries that
reduce local abundance of ribbon seal prey is unlikely to be a
significant threat to ribbon seal populations. Broad[hyphen]scale
reduction in a commercially[hyphen]fished, primary prey species could
have a significant impact, but the large groundfish fisheries in
Alaskan waters are managed to prevent depletion of the stocks; none of
those fisheries is in an overfished status.
The extraordinary reduction in Arctic sea ice that has occurred in
recent years has renewed interest in trans[hyphen]Arctic navigation
routes connecting the Atlantic and Pacific Oceans via the Northwest
Passage and the Northern Sea Route. Climate models predict that the
warming trend in the Arctic will accelerate, causing the ice to melt
earlier in the spring and resume freezing later in the fall, resulting
in an expansion of potential shipping routes and lengthening the
potential navigation season. Though few details are available regarding
actual shipping levels in the Sea of Okhotsk, resource development over
the last decade stands out as a likely significant contributor. It is
clear that considerable ship traffic is needed to support present oil
and gas operations, primarily off the northeastern coast of Sakhalin
Island and the western coast of the Kamchatka Peninsula, with future
developments pointing to an ever-growing shipping industry to support
the area's energy and minerals commerce. Large-scale commercial
fishing, which occurs in many parts of the Sea of Okhotsk, also
contributes to ship traffic there.
The most significant risk posed by shipping activities to ribbon
seals is the accidental or illegal discharge of oil or other toxic
substances carried by ships due to their immediate and potentially
long-term effects on individual animals, populations, food webs, and
the environment. Shipping activities can also affect ribbon seals
directly through noise and physical disturbance (e.g., icebreaking
vessels), as well as indirectly through ship emissions and possible
effects of introduction of invasive species.
Current and future shipping activities in the Arctic pose varying
levels of threat to ribbon seals depending on the type and intensity of
the shipping activity and its degree of spatial and temporal overlap
with the seals. These factors are inherently difficult to know or
predict, making threat assessment uncertain. Ribbon seals are typically
reported to be widely distributed in low
[[Page 41382]]
densities on sea ice during the spring reproductive season, are likely
even more dispersed during the summer and fall open-water seasons, and
are not known to congregate in large numbers. Their highly dispersed
distribution may help mitigate the risks of localized shipping threats,
such as oil spills or physical disturbance, since the impacts from such
events would be less likely to affect large numbers of seals. The fact
that nearly all shipping activity in the Arctic purposefully avoids
areas of ice and primarily occurs during the ice-free or low-ice
seasons may also help mitigate the threats of shipping to ribbon seals
since this species is closely associated with ice during the whelping,
nursing, and molting periods when the seals (especially young pups) may
be most vulnerable to shipping impacts. Icebreakers may pose special
risks to ribbon seals since they are capable of operating year-round in
all but the heaviest ice conditions and are sometimes used to escort
other types of vessels (e.g., tankers and bulk carriers) through ice-
covered areas. If icebreaking activities increase in the Arctic in the
future as expected, the likelihood of negative impacts (e.g., oil
spills, pollution, noise, and disturbance) occurring in ice-covered
areas where ribbon seals reside will likely also increase. Shipping
impacts alone may comprise a low risk to entire populations, but when
combined with the effects related to diminishing ice cover, such as
increasingly denser aggregations, the impacts may be magnified and may
play an important role in affecting the future health of populations.
Overall, the BRT judged the threats posed to ribbon seals from
other natural or man-made factors to be of moderate significance in
both the Bering Sea and the Sea of Okhotsk. We agree with the BRT's
finding.
Demographic Risks Assessment
Threats to a species' long-term persistence are manifested
demographically as risks to its abundance; productivity; spatial
structure and connectivity; and genetic and ecological diversity. These
viability criteria, outlined in McElhany et al. (2000), reflect
concepts that are well-founded in conservation biology and that
individually and collectively provide the most direct indices or
proxies of extinction risk. A species at very low levels of abundance
and with few populations will be less tolerant to environmental
variation, catastrophic events, genetic processes, demographic
stochasticity (variability in population growth rates arising from
random differences among individuals in survival and reproduction),
ecological interactions, and other processes. A rate of productivity
that is unstable or declining over a long period of time can indicate
poor resiliency to future environmental change. A species that is not
widely distributed across a variety of well-connected habitats is at
increased risk of extinction due to environmental perturbations,
including catastrophic events. A species that has lost locally adapted
genetic and ecological diversity may lack the raw resources necessary
to exploit a wide array of environments and endure short- and long-term
environmental changes.
The BRT members' assessments of the significance of demographic
risks to the persistence of ribbon seals were summarized qualitatively
using a numerical scoring system. This scoring system, which was
modeled on similar approaches used in other ESA status reviews (e.g.,
Atlantic Wolffish BRT, 2009; Butler et al., 2009; Cameron et al., 2010;
Kelly et al., 2010), was designed to elicit expert judgment about the
likelihood that the known and potential threats will impact the
species' persistence. Specifically, each BRT member considered the risk
that the population may be placed in danger of extinction by
demographic problems with abundance, productivity, spatial structure,
or diversity, within the next 50 years and the next 100 years, and then
assigned a score to each of these demographic risk categories using the
following values: 1--very low or zero risk, 2--low risk, 3--medium
risk, 4--high risk, and 5--very high risk. The average score and the
range of scores were tabulated for each of the four demographic risk
categories.
The BRT judged the demographic risks to the persistence of the
ribbon seal between now and 2050 to be very low (abundance,
productivity, and diversity) to low (spatial structure); and between
now and 2100 to be low (abundance, productivity, and diversity) to
medium (spatial structure). The medium risk score for demographic
problems associated with spatial structure primarily reflects the
anticipated direct impacts to ribbon seals stemming from loss of
habitat patches and connectivity. We concur with the BRTs findings.
To supplement the demographic risks assessment and express a
single, summarized judgment about extinction risk, each BRT member also
allocated 10 likelihood points among five time interval categories (now
to 2025, 2026 to 2050, 2051 to 2075, 2076 to 2100, and beyond 2100) to
indicate his or her judgment about the time until ribbon seals would
reach a population level of 5,000 individuals, representing a
hypothetical minimum viable population (MVP). Degree of uncertainty in
this judgment is expressed by spreading the points across the time
interval categories. In other words, if a member believed that ribbon
seals will never decline to 5,000 individuals, or at least not for a
very long time, all 10 likelihood points would be allocated to the
interval ``beyond 2100.'' Or, if the member believed strongly that
ribbon seals will reach that level in the latter half of this century,
and it is equally likely to happen in either the time interval ``2051
to 2075'' or ``2076 to 2100,'' five likelihood points would be
allocated to each of those two categories. Thus, this assignment of
likelihood points represents the opinion of BRT members as to whether
the population may decline below the hypothetical MVP in the specified
time intervals based on reasoned expert judgment. The level of 5,000
individuals was selected without regard to specific aspects of ribbon
seal life history that would determine the species' MVP size (which are
largely unknown). Rather, it was chosen as a value that has been
asserted to be useful because of its derivation as the approximate
median from a meta-analysis of MVPs for many species (Traill et al.,
2007; Traill et al., 2010). We note, however, that some have cautioned
about placing confidence in this value (Flather et al., 2011). The BRT
members assigned all likelihood points to the three time intervals
beyond 2050. Among the eleven BRT members, 0 percent of the likelihood
points was ascribed to the combined intervals from now to 2050, four
percent was ascribed to the interval 2051 to 2075, 13 percent was
ascribed to 2076 to 2100, and 83 percent was ascribed to the period
beyond 2100. In other words, the BRT's collective distribution of
points among time intervals indicating when the ribbon seal population
may decline to a hypothetical MVP was concentrated in the time interval
beyond the end of the current century. The range among BRT members in
the percentage of likelihood points assigned to the combined time
interval categories from now to 2100 was 0 percent (five BRT members)
to 50 percent (i.e., 5 points; one BRT member), reflecting the
variation in this judgment that results from sparse and uncertain
information underlying this assessment (the 5 other BRT members
assigned from 1 to 4 points). The BRT's scoring was of course
subjective, but it offers an indication of the BRT members'
professional judgment that
[[Page 41383]]
there is a low near-term extinction risk. We compared the scoring here
with the BRT's demographic risk assessment and our evaluation of the
ESA section 4(a)(1) factors above and found them consistent.
Conservation Efforts
When considering the listing of a species, section 4(b)(1)(A) of
the ESA requires consideration of efforts by any state, foreign nation,
or political subdivision of a state or foreign nation to protect the
species. Such efforts would include measures by Native American tribes
and organizations, local governments, and private organizations. Also,
Federal, tribal, state, and foreign recovery actions (16 U.S.C.
1533(f)), and Federal consultation requirements (16 U.S.C. 1536)
constitute conservation measures. In addition to identifying these
efforts, under the ESA and our Policy on the Evaluation of Conservation
Efforts (PECE; 68 FR 15100; March 28, 2003), we must evaluate the
certainty of implementing the conservation efforts and the certainty
that the conservation efforts will be effective on the basis of whether
the effort or plan establishes specific conservation objectives,
identifies the necessary steps to reduce threats or factors for
decline, includes quantifiable performance measures for monitoring
compliance and effectiveness, incorporates the principles of adaptive
management, and is likely to improve the species' viability at the time
of the listing determination.
At this time, we are not aware of any formalized conservation
efforts for ribbon seals that have yet to be implemented, or which have
recently been implemented, but have yet to show their effectiveness in
removing threats to the species. Therefore, we do not need to evaluate
any domestic conservation efforts under the PECE.
NMFS has an agreement with the Ice Seal Committee (ISC) under
section 119 of the Marine Mammal Protection Act to conserve and provide
co-management of subsistence use of ice seals by Alaska Natives. The
ISC co-manages ice seals with NMFS by monitoring subsistence harvest
and cooperating on needed research and education programs pertaining to
ice seals. NMFS's National Marine Mammal Laboratory is engaged in an
active research program for ribbon seals. The new information from
research will be used to enhance our understanding of the risk factors
affecting ribbon seals, thereby improving our ability to develop
effective management measures for the species.
ESA section 4(b)(1)(B) requires us to give consideration to species
which have been designated as requiring protection from unrestricted
commerce by any foreign nation, or pursuant to any international
agreement; or identified as in danger of extinction, or likely to
become so within the foreseeable future, by any state agency or any
agency of a foreign nation that is responsible for the conservation of
the species. We are not aware of any such special protections or
designations, or of any conservation efforts undertaken by foreign
nations specifically to protect ribbon seals. Ribbon seals are not
afforded any protective measures or special status via the Convention
for the International Trade in Endangered Species or the International
Union for Conservation of Nature.
Listing Determination
We have reviewed the status of the ribbon seal, fully considering
the best scientific and commercial data available, including the status
review report. We have reviewed the threats to the ribbon seal, as well
as other relevant factors, and given consideration to conservation
efforts and special designations for ribbon seals by states and foreign
nations. The best available information indicates that the threats
posed to the persistence of the ribbon seal from foreseeable future
destruction or modification of habitat attributable to climate change
are of greater significance than threats from other factors. Although
the trajectory of ribbon seal abundance is impossible to project with
certainty, it is likely that the effects of diminished sea ice habitat
and disrupted prey communities will reduce ribbon seal's vital rates of
reproduction and survival gradually throughout the foreseeable future.
However, our analysis did not indicate that the ribbon seal is in
danger of extinction (endangered) or that the anticipated impacts on
ribbon seal vital rates render the species likely to become an
endangered species within the foreseeable future (threatened)
throughout its range. Relevant considerations supporting this
conclusion include: (1) There is evidence from some recent years with
unusual ice conditions that ribbon seals may compensate for changes in
sea ice, as least in part, by moving to areas with better ice, at least
in the Bering Sea; (2) ribbon seals are known to have a diet that is
ecologically and trophically diverse and they are able to forage over a
wide range of ocean depths, which should enhance resilience to climate-
related changes in prey communities; (3) ribbon seals tend to be highly
dispersed and mostly solitary during the ice-free season, which would
provide a hedge against localized threats such as oil spills,
concentrations of fishery activity, and interactions with shipping; and
(4) individual ribbon seals have the capability to undertake large
seasonal movements and shifts between pelagic and pack ice habitats,
which may mitigate some anticipated impacts of anthropogenic climate
change. We therefore find that the ribbon seal does not warrant listing
as threatened or endangered throughout its range at this time.
Significant Portion of the Range Evaluation
Under the ESA and our implementing regulations, a species warrants
listing if it is threatened or endangered throughout all or a
significant portion of its range. In our analysis for this listing
determination, we initially evaluated the status of and threats to the
ribbon seal throughout its entire range. We found that the consequences
of habitat change associated with a warming climate can be expected to
manifest throughout the current breeding and molting ranges of ribbon
seals, and that the ongoing and projected changes in sea ice habitat
are likely to reduce the ribbon seal's vital rates of reproduction and
survival gradually through the foreseeable future. However, despite the
expectation of a gradual decline, we concluded that the ribbon seal is
not endangered nor is it likely to become so within the foreseeable
future throughout its range.
The magnitude of the threats posed to the persistence of ribbon
seals, including from changes in sea ice habitat, is likely to vary to
some degree across the range of the species depending on a number of
factors, including where affected populations occur. In light of the
potential differences in the magnitude of the threats to specific areas
or populations, we next evaluated whether the ribbon seal might be
threatened or endangered in any significant portion of its range. In
accordance with our draft policy on ``significant portion of its
range,'' our first step in this evaluation was to review the entire
supporting record for this listing determination to ``identify any
portions of the range[s] of the [DPSs] that warrant further
consideration'' (76 FR 77002; December 9, 2011). We evaluated whether
substantial information indicated ``that (i) the portions may be
significant [within the meaning of the draft policy] and (ii) the
species [occupying those portions] may be in danger of extinction or
likely to become so within the
[[Page 41384]]
foreseeable future'' (76 FR 77002; December 9, 2011). Depending on the
biology of a species, its range, and the threats it faces, it might be
more efficient for us to address the significance question first or the
status question first. Thus, if we determine that a portion of the
range is not ``significant,'' we do not need to determine whether the
species occupying that portion is threatened or endangered there; if we
determine that the members of a species occupying a portion of its
range are not threatened or endangered, we do not need to determine if
that portion is ``significant.'' In practice, a key part of the
determination as to whether a species is in danger of extinction in a
significant portion of its range is whether the threats are
geographically concentrated in some way. If the threats to the species
are essentially uniform throughout its range, no portion is likely to
warrant further consideration. Moreover, if any concentration of
threats to the species occurs only in portions of the species' range
that clearly would not meet the biologically based definition of
``significant,'' such portions will not warrant further consideration.
Finally, if threats, even though acting only in a portion of the range
of the species, would cause the entire species to be threatened or
endangered, the conclusion would be that the species is threatened or
endangered throughout its range (rather than only in a significant
portion of its range).
All of the ESA threat factors assigned scores by the BRT (Factors
A, B, C, and E) were judged to be of relatively higher significance in
the Sea of Okhotsk than in the Bering Sea, and we concur with this
assessment. Therefore, we evaluated whether there is substantial
information suggesting that the hypothetical loss of the portion of the
species residing in the Sea of Okhotsk would reasonably be expected to
increase the demographic risks to the point that the species would then
be in danger of extinction, i.e., whether the Sea of Okhotsk portion of
the species' range should be considered ``significant.'' At present,
the numbers of ribbon seals in both the Bering Sea and Sea of Okhotsk
portions of the range are on the order of 100,000 or more in each sea
basin. As discussed in more detail in the status review report,
populations or sub-populations of this magnitude and with the life
history characteristics of the ribbon seal are typically immune to
demographic risks that are associated with or exacerbated by low
abundance, such as year-to-year environmental fluctuations, loss of
diversity, failure of breeding systems, and lack of potential for
productivity. The climate related threats facing ribbon seals are
expected to increase more or less in parallel between the Bering Sea
and Sea of Okhotsk, albeit more quickly in the latter. If ribbon seal
numbers in the Bering Sea decrease in the future to levels at which the
demographic risks discussed above become significant, then the loss of
either the Sea of Okhotsk or the Bering Sea portions would likely place
the entire species in danger of extinction. However, at least in the
near term, the BRT concluded, and we agree, that the loss of the Sea of
Okhotsk portion of the ribbon seal population would not place the
remainder, the Bering Sea portion, in danger of extinction (Boveng et
al., 2013, section 4.3.3.3). Because the portion of the ribbon seal
population residing in the Sea of Okhotsk is not so significant that
its hypothetical loss would render the species endangered, we conclude
that the Sea of Okhotsk portion does not constitute a significant
portion of the ribbon seal's range. Consequently, we need not address
the question of whether the portion of the species occupying the Sea of
Okhotsk is threatened or endangered.
Conclusion
Our review of the information pertaining to the five ESA section
4(a)(1) factors does not support the assertion that there are threats
acting on the species or its habitat that have rendered the ribbon seal
to be in danger of extinction or likely to become so in the foreseeable
future, throughout all or a significant portion of its range.
Therefore, listing the ribbon seal as threatened or endangered under
the ESA is not warranted at this time.
We will continue to monitor the status of the ribbon seal. If
conditions change in the future, we will re-evaluate the status of this
species to determine whether it should be listed as threatened or
endangered under the ESA. Because of the remaining uncertainties
regarding the effects of climate change, sea ice cover, and potential
Russian harvests, following the 2008 status review of the ribbon seal,
this species was added to our Species of Concern list (http://www.nmfs.noaa.gov/pr/species/concern/). The Species of Concern list
serves to: (1) Increase public awareness about the species; (2) further
identify data deficiencies and uncertainties in the species' status and
the threats it faces; and (3) stimulate cooperative research efforts to
obtain the information necessary to evaluate the species' status and
threats. As resources permit, we will conduct further studies of ribbon
seal abundance and status. We will evaluate results of these and any
other studies that may be conducted and undertake a new status review,
if warranted.
References Cited
A complete list of all references cited in this rulemaking can be
found on our Web site at http://alaskafisheries.noaa.gov and is
available upon request from the NMFS office in Juneau, Alaska (see
ADDRESSES).
Authority
The authority for this action is the Endangered Species Act of
1973, as amended (16 U.S.C. 1531 et seq.).
Dated: July 3, 2013.
Alan D. Risenhoover,
Director, Office of Sustainable Fisheries, performing the functions and
duties of the Deputy Assistant Administrator for Regulatory Programs.
[FR Doc. 2013-16601 Filed 7-9-13; 8:45 am]
BILLING CODE 3510-22-P