[Federal Register Volume 76, Number 105 (Wednesday, June 1, 2011)]
[Proposed Rules]
[Pages 31556-31570]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-13627]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
50 CFR Parts 223 and 224
[Docket No. 100903415-1286-02]
RIN 0648-XW96
Endangered and Threatened Wildlife and Plants; Endangered Species
Act Listing Determination for Atlantic Bluefin Tuna
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: After we, NMFS, received a petition to list Atlantic bluefin
tuna (Thunnus thynnus) as threatened or endangered under the Endangered
Species Act (ESA), we established a status review team (SRT) to conduct
a review of the status of Atlantic bluefin tuna. We have reviewed the
SRT's status review report (SRR) and other available scientific and
commercial information and have determined that listing Atlantic
bluefin tuna as threatened or endangered under the ESA is not warranted
at this time. We also announce the availability of the SRR.
DATES: This finding is made as of May 27, 2011.
ADDRESSES: The Atlantic bluefin tuna status review report and list of
references are available by submitting a request to the Assistant
Regional Administrator, Protected Resources Division, Northeast Region,
NMFS, 55 Great Republic Way, Gloucester, MA 01930. The status review
report and other reference materials regarding this determination can
also be obtained via the Internet at: http://www.nero.noaa.gov/prot_res/CandidateSpeciesProgram/cs.htm.
FOR FURTHER INFORMATION CONTACT: Kim Damon-Randall, NMFS Northeast
Regional Office, (978) 282-8485; or Marta Nammack, NMFS, Office of
Protected Resources (301) 713-1401.
SUPPLEMENTARY INFORMATION:
Background
On May 24, 2010, the National Marine Fisheries Service (NMFS)
received a petition from the Center for Biological Diversity (CBD)
(hereafter referred to as the Petitioner), requesting that we list the
entire species of Atlantic bluefin tuna (Thunnus thynnus) or in the
alternative, an Atlantic bluefin tuna distinct population segment (DPS)
consisting of one or more subpopulations in United States waters, as
endangered or threatened under the ESA, and designate critical habitat
for the species. The petition contains information on the species,
including the taxonomy; historical and current distribution; physical
and biological characteristics of its habitat and ecosystem
relationships; population status and trends; and factors contributing
to the species' decline. The Petitioners also included information
regarding possible DPSs of Atlantic bluefin tuna. The petition
addresses the five factors identified in section 4(a)(1) of the ESA as
they pertain to Atlantic bluefin tuna: (A) Current or threatened
habitat destruction or modification or curtailment of habitat or range;
(B) overutilization for commercial purposes; (C) disease or predation;
(D) inadequacy of existing regulatory mechanisms; and (E) other natural
or man-made factors affecting the species' continued existence.
On September 21, 2010, we determined that the petition presented
substantial information indicating that the petitioned action may be
warranted and published a positive 90-day finding in the Federal
Register (FR) (75 FR 57431). Following our positive 90-day finding, we
convened an Atlantic bluefin tuna status review team (SRT) to review
the status of the species.
In order to conduct a comprehensive review, we asked the SRT to
assess the species' status and degree of threat to the species with
regard to the factors provided in Section 4(a)(1) of the ESA without
making a recommendation regarding listing. The SRT was provided a copy
of the petition and all information submitted in response to the data
request in the FR notice announcing the 90-day finding. In order to
provide the SRT with all available information, we invited several
Atlantic bluefin tuna experts to present information on the life
history, genetics, and habitat used by Atlantic bluefin tuna to the
SRT.
We also hosted five listening sessions with Atlantic bluefin tuna
fishermen. These sessions were held in Maine, Massachusetts, New
Jersey, North Carolina, and Mississippi. Those with information
relevant to the discussion topics for the sessions were also encouraged
to submit information via mail or electronic mail. The SRT reviewed all
this information during its consideration and analysis of potential
threats to the species. The SRR is a summary of the information
assembled by the SRT and incorporates the best scientific and
commercial data available
[[Page 31557]]
(e.g., fisheries data that are available to assist in assessing the
status of the species). In addition, the SRT summarized current
conservation and research efforts that may yield protection, and drew
scientific conclusions about the status of Atlantic bluefin tuna
throughout its range.
The SRT completed a draft SRR in March 2011. As part of the full
evaluation of the status of Atlantic bluefin tuna under the ESA, we
requested that the Center for Independent Experts (CIE) select three
independent experts to peer review the SRR. The reviewers were asked to
provide written summaries of their comments to ensure that the content
of the SRR is factually supported and based on the best available data,
and the methodology and conclusions are scientifically valid. Prior to
finalizing the SRR, the SRT considered and incorporated, as
appropriate, the peer reviewers' comments. The final SRR was submitted
to us on May 20, 2011.
Range
Atlantic bluefin tuna are highly migratory pelagic fish that range
across most of the North Atlantic and its adjacent seas, particularly
the Mediterranean Sea. They are the only large pelagic fish living
permanently in temperate Atlantic waters (Bard et al., 1998, as cited
in Fromentin and Fonteneau, 2001). In the Atlantic Ocean and adjacent
seas, they can range from Newfoundland south to Brazil in the western
Atlantic, and in the eastern Atlantic from Norway south to western
Africa (Wilson et al., 2005).
Habitat and Migration
Atlantic bluefin tuna are epipelagic and typically oceanic;
however, they do come close to shore seasonally (Collette and Nauen,
1983). They often occur over the continental shelf and in embayments,
especially during the summer months when they feed actively on herring,
mackerel, and squids in the North Atlantic. Larger individuals move
into higher latitudes than smaller fish. Surface temperatures where
large Atlantic bluefin tuna have been found offshore in the northwest
Atlantic range between 6.4 and 28.8 [deg]C, whereas smaller Atlantic
bluefin tuna are generally found in warmer surface water ranging from
15 to 17 [deg]C (Collette and Klein-MacPhee, 2002). In general,
Atlantic bluefin tuna occupy surface waters around 24 [deg]C in the
Western Atlantic (Block et al., 2005; Teo et al., 2007) and in the
Eastern Atlantic/Mediterranean, generally around 20.5 to 21.5 [deg]C
(Royer et al., 2004) and above 24 [deg]C for spawning (Mather et al.,
1995; Schaefer, 2001; Garcia et al., 2005).
Archival tagging and tracking information have confirmed that
Atlantic bluefin tuna are endothermic (i.e., able to endure cold as
well as warm temperatures while maintaining a stable internal body
temperature). It was once thought that Atlantic bluefin tuna
preferentially occupy surface and subsurface waters of the coastal and
open-sea areas; however, data from archival tagging and ultrasonic
telemetry indicate that they frequently dive to depths of 500 m to
1,000 m (Lutcavage et al., 2000). While they do dive frequently to
deeper depths, they generally spend most of their time in waters less
than 500 m, and often much shallower.
As stated previously, Atlantic bluefin tuna are highly migratory;
however, they do display homing behavior and spawning site fidelity in
both the Gulf of Mexico and the Mediterranean Sea, and these two areas
constitute the two primary spawning areas identified to date. Larvae
have, however, been documented outside of the Gulf of Mexico in the
western Atlantic, and the possibility of additional spawning areas
cannot be discounted (McGowan and Richards, 1989).
It appears that larvae are generally retained in the Gulf of Mexico
until June, and schools of young-of-the-year (YOY) begin migrating to
juvenile habitats (McGowan and Richards, 1989) thought to be located
over the continental shelf around 34[deg]N and 41[deg]W in the summer,
and further offshore in the winter. They have also been identified from
the Dry Tortugas area in June and July (McGowan and Richards, 1989;
ICCAT, 1997). Juveniles migrate to nursery areas located between Cape
Hatteras, North Carolina and Cape Cod, Massachusetts (Mather et al.,
1995).
Atlantic bluefin tuna have not been observed spawning (Richards,
1991); however, recent work has identified putative breeding behaviors
by Atlantic bluefin tuna while in the Gulf of Mexico (Teo et al.,
2007). Presumed Atlantic bluefin tuna breeding behaviors were
associated with bathymetry (continental slope waters), sea surface
temperature (moderate), eddy kinetic energy (moderate), surface
chlorophyll (low concentrations), and surface wind speed (moderate)
(Teo et al., 2007).
Western Atlantic
Essential fish habitat (EFH) is defined under the Magnuson-Stevens
Act as waters, aquatic areas and their associated physical, chemical,
and biological properties that are used by fish and may include aquatic
areas historically used by fish where appropriate; and the substrate,
sediment, hard bottom, structures underlying the waters, and associated
biological communities that are necessary to fish for spawning,
breeding, feeding, or growth to maturity, representing the species full
life cycle.
For western Atlantic bluefin tuna, EFH was defined in the Final
Amendment 1 to the Consolidated Highly Migratory Species Fishery
Management Plan (NMFS Amendment 1, 2009). Atlantic bluefin tuna EFH for
spawning, eggs, and larvae was defined as following the 100 m depth
contour in the Gulf of Mexico to the Exclusive Economic Zone (EEZ), and
continuing to the mid-east coast of Florida. For juveniles sized less
than 231 cm fork length (FL), EFH was defined as waters off North
Carolina, south of Cape Hatteras to Cape Cod. For adult sizes equal to
or greater than 231 cm FL, it was defined as pelagic waters of the
central Gulf of Mexico and the mid-east coast of Florida, North
Carolina from Cape Lookout to Cape Hatteras, and New England from
Connecticut to the mid-coast of Maine.
It is believed that there are certain features of the Atlantic
bluefin tuna larval habitat in the Gulf of Mexico which determine
growth and survival rates and that these features show variability from
year to year, perhaps accounting for a significant portion of the
fluctuation in yearly recruitment success (McGowan and Richards, 1989).
The habitat requirements for larval success are not known, but larvae
are collected within narrow ranges of temperature and salinity;
approximately 26 [deg]C and salinities of 36 parts per thousand (ppt).
Along the coast of the southeastern United States, onshore meanders of
the Gulf Stream can produce upwelling of nutrient rich water along the
shelf edge. In addition, compression of the isotherms on the edge of
the Gulf Stream can form a stable region which, together with upwelling
nutrients, provides an area favorable to maximum growth and retention
of food for the larvae (McGowan and Richards, 1989).
Additionally, NMFS Amendment 1 designated a Habitat Area of
Particular Concern (HAPC) for bluefin tuna. The bluefin tuna HAPC is
located west of 86 [deg] W and seaward of the 100 m isobath, extending
from the 100 m isobath to the EEZ. The area includes a majority of the
locations where Atlantic bluefin tuna larval collections have been
documented, overlaps with adult and larval Atlantic bluefin tuna EFH,
and incorporates portions of an area identified as a primary spawning
[[Page 31558]]
location by Teo et al. (2007). The Gulf of Mexico is believed to be the
primary spawning area for western Atlantic bluefin tuna, and the HAPC
designation highlights the importance of the area for Atlantic bluefin
tuna spawning. It may also provide added conservation benefits if steps
are taken to reduce impacts from development activities through the
consultation process.
Eastern Atlantic
The best known spawning areas for the eastern Atlantic bluefin tuna
are southwest of the Balearic Sea, the central and southern Tyrrhenian
Sea, the central Mediterranean Sea southwest of Malta, and the eastern
Mediterranean Sea in the south Aegean to the area north of Cyprus,
particularly the area between Anamur and Mersin in the Levantine Sea.
Important spatial changes in some of the most relevant spawning areas
have been noticed in the last 10 years, particularly in the south
Tyrrhenian and central Mediterranean. Most of the available information
reports a major presence of bluefin tuna along the coasts of Croatia,
south Adriatic Sea, western Ionian Sea, Tyrrhenian Sea, all the
northwestern Mediterranean coast, in some areas of Morocco and Tunisia,
in a few Aegean areas, and in the Levantine Sea (between Anamur and
Mersin).
Areas where juveniles concentrate have been noticed to change from
year to year. Juveniles are mostly present in feeding aggregations or
schools during fall, from September to December. Mature specimens have
been reported from most of the Mediterranean areas, with the only
exceptions being the Gulf of Lions and the northern Adriatic Sea.
Larvae have also been found in most of the Mediterranean surface
waters, with a major concentration in areas where gyres and fronts are
present, particularly in the second part of summer.
Young-of-the-year (YOY) Atlantic bluefin tuna have been found
mostly in coastal areas over the continental shelf, whenever preferred
prey is present. Tagging data showed that Atlantic bluefin tuna
movement within the Mediterranean Sea is often limited, particularly
for individuals tagged in the eastern regions of the basin. Movements
of Atlantic bluefin tuna tagged in the central and western
Mediterranean Sea were more pronounced than those tagged in the eastern
portion. Seasonal prey abundance drives the concentration of both young
and adult specimens in those Mediterranean Sea areas not used for
reproduction (e.g. Ligurian Sea, north-central Adriatic Sea). Many
larger individuals (> 150 kg) move out of the Mediterranean, and their
movement patterns and displacement distance seem to be related to size
and the exploitation of feeding grounds outside the Mediterranean Sea
(Wurtz, 2010), while some are resident year round.
Consideration as a Species Under the ESA
According to Section 3 of the ESA, the term ``species'' includes
``any subspecies of fish or wildlife or plants, and any distinct
population segment of any species of vertebrate fish or wildlife that
interbreeds when mature.'' Congress included the term ``distinct
population segment'' in the 1978 amendments to the ESA. On February 7,
1996, the U.S. Fish and Wildlife Service and NMFS (jointly referred to
as the Services) adopted a policy to clarify their interpretation of
the phrase ``distinct population segment'' for the purpose of listing,
delisting, and reclassifying species (61 FR 4721). The policy described
two criteria a population segment must meet in order to be considered a
DPS (61 FR 4721):
1. It must be discrete in relation to the remainder of the species
to which it belongs; and
2. It must be significant to the species to which it belongs.
Determining if a population is discrete requires 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.
If a population is deemed discrete, then the population segment is
evaluated in terms of significance, which may include, but is not
limited to, the following:
1. Persistence of the discrete population segment in an ecological
setting unusual or unique for the taxon.
2. Evidence that loss of the discrete population segment would
result in a significant gap in the range of the taxon.
3. Evidence that the discrete population segment represents the
only surviving natural occurrence of a taxon that may be more abundant
elsewhere as an introduced population outside its historic range; or
4. Evidence that the discrete population segment differs markedly
from other populations of the species in its genetic characteristics.
If a population segment is deemed discrete and significant, then it
qualifies as a DPS.
Discreteness
Rooker et al. (2008) analyzed the chemical composition of otoliths
(e.g., fish ear bones) from Atlantic bluefin tuna that were 12 to 18
months of age and that were caught between 1999 and 2004 in both the
eastern (Mediterranean Sea/eastern Atlantic Ocean) and western (Gulf of
Mexico/eastern coast of the United States) nurseries. These authors
found that otolith composition was distinct between yearlings from the
two different nursery areas, and that the chemical signature was
significantly different for yearlings from the eastern nursery in five
of the years (all except 2001) (Rooker et al., 2008).
Dickhut et al. (2009) used organochlorine and polychlorinated
biphenyl (PCB) tracers from Atlantic bluefin tuna foraging grounds to
determine the rate of mixing of different size classes between the
eastern and western stocks. Their results indicated that mixing of
juvenile Atlantic bluefin tuna from the eastern to the western foraging
grounds could be as high as 80 percent for certain age classes and that
juveniles from the Mediterranean Sea may migrate to western Atlantic
foraging grounds as early as age 1 (Dickhut et al., 2009). However,
this study also indicated that medium to giant sized Atlantic bluefin
tuna entering the Gulf of Mexico breeding grounds showed PCB ratios
similar to that of the western Atlantic young-of-the-year (YOY), which
suggests little or no mixing on the spawning grounds in the Gulf of
Mexico, as these fish have been foraging in the western Atlantic rather
than foraging grounds used by Mediterranean bluefin tuna (Dickhut et
al., 2009).
Carlsson et al. (2006) conducted analyses of 320 YOY Atlantic
bluefin tuna to evaluate the hypothesis that 2 separate spawning
grounds exist for the western and eastern stocks--Gulf of Mexico and
Mediterranean Sea, respectively. In this study, Carlsson et al. (2006)
conducted a microsatellite analysis of 8 loci and examined the
mitochondrial DNA control region and found significant genetic
differentiation among YOY fish captured in the Gulf of Mexico spawning
grounds versus those captured in the Mediterranean spawning area. Their
results support a high degree of spawning site fidelity, and thus, they
noted that the recognition of genetically distinct populations requires
independent
[[Page 31559]]
management of the stocks of this species (Carlsson et al., 2006).
Riccioni et al. (2010) indicated that genetic analyses and
microchemical signatures from otoliths strongly support the existence
of two distinct primary spawning areas for Atlantic bluefin tuna (the
Mediterranean and Gulf of Mexico). These authors noted that significant
genetic divergence was found between these two spawning stocks using
microsatellite (Carlsson et al., 2007) and mitochondrial DNA analyses
(Boustany et al., 2008), and they also indicated that there are high
rates of spawning site fidelity of 95.8 percent and 99.3 percent for
the Mediterranean Sea and Gulf of Mexico, respectively (Rooker et al.,
2008; Block et al., 2005).
The best available information indicates that fish from the
Mediterranean stock, while making some trans-Atlantic migrations,
return to the Mediterranean to spawn while fish from the Gulf of Mexico
stock return to the Gulf of Mexico to spawn. This separation between
the stocks is supported by the aforementioned genetic analyses which
indicate significant genetic differentiation between the two stocks as
described above. In addition, the results of the otolith microchemistry
analyses indicate that natal homing or spawning site fidelity does
occur, and the study by Dickhut et al. (2009) using organochlorine and
PCB tracers also indicate that there is little to no mixing on the
spawning grounds. Furthermore, according to Rooker et al. (2008), the
rates of spawning site fidelity are 95.8 percent and 99.3 percent for
the Mediterranean Sea and Gulf of Mexico, respectively. Thus, the two
populations in the North Atlantic are discrete.
The available data further suggest that the eastern Atlantic stock
exhibits genetic differentiation, spatial separation during spawning as
a result of spawning site fidelity/natal homing, and differences in
behavior (e.g., some resident fish in the eastern Mediterranean versus
non-resident/migratory fish in the western Mediterranean) with
different spawning areas in the western and eastern Mediterranean.
According to Reeb (2010), the eastern and western basins of the
Mediterranean exhibit differences in temperature, circulation patterns,
and salinity, and the basins are considered oceanographically to be
separated by the straits of Sicily and Messina. Thus, even though
Atlantic bluefin tuna are highly migratory, the areas that they home to
in order to spawn may possess unique characteristics. All of this
evidence combined with the recent evidence suggesting a separate
spawning area in the eastern Mediterranean and genetic analyses which
demonstrate significant genetic differences between western and eastern
Mediterranean fish and between the Mediterranean and Gulf of Mexico
spawning areas led Fromentin (2009) to hypothesize that Atlantic
bluefin tuna are comprised of at least three sub-populations: (1) A
highly migratory stock over all of the North Atlantic that spawns in
western and central Mediterranean areas; (2) a more resident stock in
the Mediterranean which spawns in the central and eastern
Mediterranean; and (3) a more resident stock in the West Atlantic which
spawns in the Gulf of Mexico. As such, two discrete populations may
exist within the larger eastern Mediterranean population. While there
is some evidence which indicates that there may be other, discrete
spawning areas outside of the Gulf of Mexico, the locations of these
areas have not been confirmed or fully described at this time.
Using the best available information, the SRT concluded that the
western Atlantic and the eastern Atlantic populations are discrete from
each other. Within the eastern Atlantic, the available information
suggests that there may be two discrete populations of Atlantic bluefin
tuna; however, the data are inconclusive regarding the Mediterranean at
this time.
Significance
If a population is deemed discrete, then the population segment is
evaluated in terms of significance. The western Atlantic population has
been determined to be a discrete population from the two possible
Mediterranean populations as described above. Consequently, it is
necessary to assess the biological and ecological significance of each
discrete population as described in the Services' DPS policy.
Several studies have documented that Atlantic bluefin tuna in the
Mediterranean appear to prefer sea surface temperatures above 24 [deg]C
for spawning (Mather et al., 1995; Schaefer, 2001; Garcia et al.,
2005), and in the Gulf of Mexico, Teo et al. (2007) noted that they
prefer areas with surface temperatures between 24 and 27 [deg]C. Since
adult Atlantic bluefin tuna are present in the Gulf of Mexico as early
as winter but are not usually in spawning condition until mid-April
(Block et al., 2001), an environmental cue such as temperature or
photoperiod may trigger spawning (Muhling et al., 2010).
Muhling et al. (2010) also indicated that Atlantic bluefin tuna
larvae are generally absent from continental shelf areas with low
surface temperatures and salinities at the beginning of the spawning
period. They theorized that Atlantic bluefin tuna may avoid spawning in
these areas as they are typically high in chlorophyll concentrations
and, therefore, contain dense phytoplankton blooms which support high
concentrations of zooplankton. While the high concentrations of
zooplankton provide a source of larval prey, they attract other
planktonic predators (Bakun, 2006). According to Muhling et al. (2010),
larval tuna have specialized diets, often feeding on pelagic tunicates
found in oligotrophic open ocean areas (Sommer and Stibor, 2002, as
cited in Muhling et al., 2010). Thus, these authors concluded that
larval tuna in the Gulf of Mexico may be adapted to survive in nutrient
poor waters. Muhling et al. (2010) concluded that favorable habitat for
Atlantic bluefin tuna larvae in the Gulf of Mexico consists of areas of
moderately warm water temperatures outside of the loop current, loop
current eddies, and outside of continental shelf waters that contain
cooler water with higher chlorophyll concentrations (Muhling et al.,
2010).
Oray and Karakulak (2005) described the spawning area surveyed in
the northern Levantine Sea as containing waters with sea surface
temperatures between 21.8 to 29.3 [deg]C, salinity from 34.9 to 38.8
ppt, and depths between 63 to 2,448 m. Oray and Karakulak (2005)
indicate that larval Atlantic bluefin tuna were found in areas with
physical oceanographic features such as cyclonic eddies, which may
indicate that the main larval populations are within these cyclonic
eddies and that the tuna spawning site is within close proximity to the
area in which the larvae were observed. According to Oray and Karakulak
(2005), the optimal seawater temperatures in the Atlantic bluefin tuna
spawning area in the northern Levantine Sea are between 23 to 25
[deg]C, which generally occur early in June, whereas optimum
temperatures for spawning in the western Mediterranean generally occur
later, toward the end of June.
Garcia et al. (2005) characterized the Atlantic bluefin tuna
spawning habitat off the Balearic Archipelago. These authors noted that
Atlantic bluefin tuna larval abundance is associated with surface water
temperatures between 24 and 25 [deg]C in areas of inflowing Atlantic
waters or transitional areas with Atlantic waters mixing with
Mediterranean waters and that generally possess hydrographic features
such as fronts and gyres (Garcia et al., 2005).
[[Page 31560]]
According to Garcia et al. (2005), significant concentrations of
Atlantic bluefin tuna larvae were found off the Mallorca channel in an
area with frontal formations and south of Minorca where an anticyclonic
gyre was observed. Garcia et al. (2005) note that these frontal
structures and gyres may play an important role in providing
concentrated prey resources for larval fish, which may in turn
constitute an important part of the diet of larval Atlantic bluefin
tuna. Low and isolated larval concentrations were observed in
Mediterranean water masses north of the islands (Garcia et al., 2005).
The strong eastward current that flows from Ibiza towards Minorca may
act as a transport mechanism for larvae (Garcia et al., 2005). The area
near Mallorca and the Ibiza channels is generally characterized by low
concentrations of chlorophyll a, which is primarily due to the major
influence of the nutrient poor water masses originating from the
Atlantic (Garcia et al., 2005).
While spawning areas for Atlantic bluefin tuna may at times be
stressful environments, Atlantic bluefin tuna migrate long distances to
reach the particular areas in which they spawn (Block et al., 2001),
and homing fidelity to these sites is high. Muhling et al. (2010)
concluded that adults are targeting specific areas and oceanographic
features in order to maximize larval survival. Consequently, the
spawning areas in the Gulf of Mexico and Mediterranean are unique
ecologically and possess the features (e.g., appropriate water
conditions such as temperatures, depths, salinities, and chlorophyll
concentrations, hydrography) that are necessary for maximizing bluefin
tuna spawning success for each population.
As noted previously, Atlantic bluefin tuna exhibit strong natal
homing or spawning site fidelity. Therefore, it is unlikely individuals
from the Mediterranean would spawn in the Gulf of Mexico, or that
individuals from the Gulf of Mexico population would spawn in the
Mediterranean. Thus, if one of the discrete populations was to be
extirpated, it would represent a significant gap in the range of the
taxon, in that either the Gulf of Mexico or the Mediterranean Sea would
no longer support Atlantic bluefin tuna.
As presented above and as noted in the discreteness discussion,
Atlantic bluefin tuna that spawn in the Gulf of Mexico and in the
Mediterranean utilize unique ecological areas for spawning. There is
information presented above that indicates that these areas possess
unique features or characteristics to which larval tuna may be adapted.
Also, some authors indicated that natal homing may be the result of
behavior learned from older fish in the population and thus, the loss
of a spawning group or of the mature fish could result in the permanent
loss of a spawning area, and this area would most likely not be re-
colonized by fish from another spawning group. This would represent a
significant gap in the range of the taxon.
There is some evidence suggesting that there may be two discrete
populations within the Mediterranean, but the SRT is unable to
determine the significance of these populations to the species as a
whole. While the two Mediterranean populations may be discrete, the SRT
does not have enough information to conclude that they are significant,
by themselves, to Atlantic bluefin tuna.
Based on the best available information, the SRT concluded that the
western Atlantic and eastern Atlantic/Mediterranean populations
represent two DPSs of Atlantic bluefin tuna. We agree with the SRT's
DPS delineation, and refer to these DPSs as the western Atlantic DPS
and eastern Atlantic/Mediterranean DPS of Atlantic bluefin tuna. The
information presented in the remainder of this finding, therefore,
pertains to the status of the western Atlantic and eastern Atlantic/
Mediterranean DPSs of Atlantic bluefin tuna.
ICCAT Stock Assessment Summary for Atlantic Bluefin Tuna
Atlantic bluefin tuna are managed domestically by NMFS' Highly
Migratory Species (HMS) Management Division and internationally by the
International Commission for the Conservation of Atlantic Tunas
(ICCAT). ICCAT manages the western Atlantic and eastern Atlantic/
Mediterranean DPSs as two separate stocks (eastern and western stocks),
separated by the 45 [deg] W meridian. In recent years, stock
assessments for Atlantic bluefin tuna have been conducted approximately
every 2 years by the Standing Committee on Research and Statistics
(SCRS). The most recent ICCAT stock assessment was conducted by SCRS in
2010. Models and methodologies employed by ICCAT during the stock
assessments were used by the SRT to develop an extinction risk
analysis; therefore, a description of the models, methods, and results
is provided in the SRR, and significant conclusions are summarized
below.
Abundance of the Western Atlantic DPS of Atlantic Bluefin Tuna
According to the ICCAT SCRS stock assessment in 2010, the total
catch for the western Atlantic peaked at 18,671 t (16,938.05 mt) in
1964, with catches dropping sharply thereafter with the collapse of the
Atlantic bluefin tuna longline fishery off Brazil in 1967 and the
decline in purse seine catches. Catch increased again to average over
5,000 t (4,535.92 mt) in the 1970s due to the expansion of the Japanese
longline fleet into the northwest Atlantic and Gulf of Mexico, and an
increase in purse seine effort targeting larger fish for the sashimi
market.
Since 1982, the total catch for the western Atlantic including
discards has generally been relatively stable due to the imposition of
quotas by ICCAT. However, following a total catch level of 3,319 t
(3,010.95 mt) in 2002 (the highest since 1981), total catch in the
western Atlantic declined steadily to a level of 1,638 t (1,485.97 mt)
in 2007 (the lowest level since 1982), before rising to 1,935 t
(1,755.4 mt) in 2009, which was near the total allowable catch (TAC).
The decline prior to 2007 was primarily due to considerable reductions
in catch levels for U.S. fisheries. The major harvesters of western
Atlantic bluefin tuna are Canada, Japan, and the United States.
Safina and Klinger (2008) summarized ICCAT management regulations
and catch history for the western Atlantic stock; however, it was not a
quantitative assessment of the stock. Due to the timing of publication,
the authors were only able to consider catch data through 2006, and
there have been changes to the western Atlantic bluefin tuna fishery
since then. MacKenzie et al. (2009) projected a similar collapse;
however due to timing of publication, they were also only considering
catch data through 2006. The 2006 U.S. catches of Atlantic bluefin tuna
were the lowest in recent history; however, since then, the U.S.
fishery has seen increasing catches, and the U.S. base quota was fully
realized in 2009 and 2010. MacKenzie et al. (2009) projected that by
2011, the adult population of Atlantic bluefin tuna would be 75 percent
lower than the population in 2005. Furthermore, Safina and Klinger
(2008) stated that ``these trends [in U.S. catches] suggest U.S.
bluefin may approach widespread commercial unavailability as early as
2008''; however, the results of the ICCAT 2010 bluefin tuna stock
assessment (as described in more detail below) and the catch statistics
submitted to ICCAT clearly refute these assertions.
[[Page 31561]]
The base case assessment is consistent with previous analyses in
that spawning stock biomass (SSB) declined dramatically between the
early 1970s and early 1990s. Since then, SSB was estimated to have
fluctuated between 21 and 29 percent of the 1970 level, but with a
gradual increase in recent years from the low of 21 percent in 2003 to
29 percent in 2009. Thus, the stock has undergone substantial declines
since historic highs were reported in the 1970s. The stock has
experienced different levels of fishing mortality over time, depending
on the size of fish targeted by various fleets. Fishing mortality on
spawners (ages 9 and older) declined markedly after 2003. The estimates
of recruitment (age 1) are very high for the early 1970s, but are much
lower for the years since, with the exception of a strong year-class
documented in 2003.
There are two alternative spawner-recruit hypotheses for the
western stock: the two-line (low recruitment potential scenario) and
the Beverton and Holt spawner-recruit formulation (high recruitment
potential scenario). Under the low recruitment scenario, average levels
of observed recruitment are based on levels from 1976-2006 (85,000
recruits) while in the high recruitment scenario, recruitment levels
increase as the stock rebuilds (MSY level of 270,000 recruits). SCRS
has indicated that it does not have strong evidence to favor either
scenario over the other and notes that both are reasonable (but not
extreme) lower and upper bounds on rebuilding potential. Both of these
models take into account multiple variables affecting abundance,
including fishing mortality, recruitment and vulnerabilities, and
terminal ages. During the 2010 stock assessment, the SCRS re-examined
the two alternative spawner-recruit hypotheses explored in several
prior assessments. Stock status was determined under both scenarios for
the base model from 1970 to 2009. The results under the two-line (low
recruitment potential) scenario suggested that the stock has not been
overfished since 1970, and that overfishing has not occurred since
1983. The results under the Beverton-Holt (high recruitment potential)
scenario suggested that the stock has been overfished since 1970, and
the fishing mortality rates (F) have been above fishing at maximum
sustainable yield (FMSY), except for the years 1985, 1986,
and 2007 to 2009. The low recruitment scenario is the more optimistic
scenario because the result is that the stock biomass is above the
rebuilding goal. Under the high recruitment scenario, rebuilding cannot
be met by the end of ICCAT's 20-year rebuilding period. However, it is
important to note that this change in the perception of current stock
status (to not overfished, no overfishing occurring) under the low
recruitment scenario is largely the result of applying a new growth
curve rather than the result of management measures under the
rebuilding plan.
ICCAT estimated the status of the western Atlantic stock in 2009 as
well as status trajectories for the two recruitment levels. Using MSY-
related benchmarks, ICCAT determined that the western Atlantic stock is
not overfished and is not undergoing overfishing under the low
recruitment potential scenario. However, under the Beverton-Holt
recruitment hypothesis (high recruitment potential scenario), the stock
remains overfished and overfishing is occurring. It was noted, however,
that the assessment did not capture the full degree of uncertainty in
the assessments and projections. Based on earlier work, the estimates
of stock status can be expected to vary considerably depending on the
type of data used to estimate mixing (conventional tagging or isotope
signature samples) and modeling assumptions made. Improved knowledge of
maturity at age will also affect the perception of changes in stock
size. Finally, the lack of representative samples of otoliths requires
determining the catch at age from length samples, which is imprecise
for larger Atlantic bluefin tuna.
The results of the 2010 stock assessment for western Atlantic
bluefin tuna were strongly influenced by a new growth curve (Restrepo
et al., 2010). The new growth curve assigns older ages to fish larger
than 120 cm. As a result, the age structure of the catch included a
higher proportion of older fish, which implied that the stock was
subjected to a lower fishing mortality than previously estimated. Under
the low recruitment potential scenario, therefore, SSB was now
estimated to have greater than a 60 percent chance of being above the
level that will support MSY, and overfishing is not occurring. SSB
remained low relative to the level at MSY under the high recruitment
potential scenario. The fishing mortality rate under the high
recruitment potential scenario indicated overfishing was still
occurring.
Under both scenarios, the SSB trend shows an increase in the last
few years of the time series considered. The SCRS also noted the
strength of the 2003 year class, the largest since 1974, although it
also acknowledged that the recruitment estimated by the model for
subsequent year classes appears to be the lowest on record and,
therefore, these subsequent year classes may be a cause of concern.
However, anecdotal information from U.S. recreational and commercial
fishermen pointed to a perceived high abundance of small Atlantic
bluefin tuna in U.S. waters in 2010.
The SCRS noted that the productivity of both the western Atlantic
bluefin tuna and western Atlantic bluefin tuna fisheries is linked to
the eastern Atlantic/Mediterranean stock. There is very strong evidence
that eastern DPS fish contribute to the catches that occur along the
eastern seaboard of North America, particularly in the Mid-Atlantic
Bight. Consequently, improvements to the stock status in the eastern
DPS, which result in increases to the number of eastern fish in the
Mid-Atlantic Bight fishery, could reduce the proportion of the TAC that
comes from western DPS fish. Therefore, management actions taken in the
eastern Atlantic and Mediterranean are likely to influence the recovery
in the western Atlantic, because even small rates of mixing from the
eastern Atlantic/Mediterranean to the western Atlantic can have
significant effects on the western Atlantic due to the fact that the
eastern Atlantic/Mediterranean resource is much larger than that of the
western Atlantic (i.e., approximately 10 times the size).
Abundance of the Eastern Atlantic/Mediterranean DPS of Atlantic Bluefin
Tuna
Reported catches in the eastern Atlantic/Mediterranean peaked at
over 50,000 t (45,359.24 mt) in 1996 and then decreased substantially,
stabilizing around TAC levels established by ICCAT. Both the increase
and the subsequent decrease in declared production occurred mainly for
the Mediterranean. Available information showed that catches of
Atlantic bluefin tuna from the eastern Atlantic/Mediterranean were
seriously under-reported from 1998 to 2007. In addition, farming
activities in the Mediterranean since 1997 significantly changed the
fishing strategy of purse seiners and resulted in a deterioration of
Atlantic bluefin tuna catch at size (CAS) data reported to ICCAT. This
is because Atlantic bluefin tuna size samples were obtained only at the
time of harvest from the farms and not at the time of capture. The 2008
and 2009 reported catch was reviewed by the SCRS during the Atlantic
bluefin tuna data preparatory meeting. The SCRS indicated that the
reporting of catches significantly improved in those 2 years. However,
the SCRS also indicated that
[[Page 31562]]
some misreporting could still have been taking place. The assessment
for the eastern stock used data for the period 1950-2009. Historically,
illegal, unreported and unregulated fishing resulted in catch levels
far exceeding the TAC levels mandated by ICCAT in the east. The United
States has been looking closely at eastern bluefin tuna compliance and
IUU issues over the years. Indications over the last two years are that
progress has been made to address non-compliance and IUU issues, and
catches over the last two years appear to be in line with agreed limits
based on the monthly catch reports and SCRS information. Recruitment at
the start of the time series varied between 2 and 3 million fish,
dropped to around 1 million fish during the 1960s, followed by a steady
increase toward maximum values in the 1990s and early 2000s while
recruits dropped steeply in the last years. However, the recent levels
are known to be less reliable because of the lack of data to estimate
them. SCRS also notes that the potential decline in the recruitment in
the most recent years is not in agreement with scientific information
from aerial surveys carried out in the Mediterranean Sea (Bonhommeau et
al., 2009).
Final SSB estimates differed slightly between the model runs that
were used. The SSB peaked over 300,000 t (272,155.42 mt) in the late
1950s and early 1970s, followed by a decline. One model run indicated
that the SSB continued to decline slightly to about 150,000 t
(136,077.71 mt), while the other indicated that biomass increased
slightly during the late 2000s to about 200,000 t (181,436.95 mt).
Considering both runs, the analyses indicated that recent (2007-2009)
SSB is about 57 percent of the highest estimated SSB levels (1957-
1959).
Significant Portion of Its Range and Foreseeable Future
The ESA defines an ``endangered species'' as ``any species which is
in danger of extinction throughout all or a significant portion of its
range,'' while a ``threatened species'' is defined as ``any species
which is likely to become an endangered species within the foreseeable
future throughout all or a significant portion of its range.'' The
phrase ``throughout all or a significant portion of its range'' is
neither defined nor explained in the ESA, and a final policy on how to
interpret this language has not been developed by NMFS.
As previously noted, Atlantic bluefin tuna are highly migratory
pelagic fish that range across most of the North Atlantic and its
adjacent seas, particularly the Mediterranean Sea. Although the
Atlantic bluefin tuna DPSs are described or defined by the location of
their spawning grounds, they use the Atlantic Ocean and adjacent seas
for various life stages and migrations for foraging, nursery grounds,
and spawning. If a DPS was threatened or endangered in a spawning area,
it would be threatened or endangered throughout its range (and not only
in the spawning area) because a species cannot survive if individuals
cannot spawn. Therefore, any determination we would make on the status
of the DPSs would be based on the status of the DPSs throughout their
ranges.
During a meeting to discuss the SRR, the SRT also considered the
foreseeable future for Atlantic bluefin tuna and estimated the mean
generation time for both the eastern Atlantic/Mediterranean DPS and
western Atlantic DPS. For the purpose of the SRR, the mean generation
time was determined to be 17 years for the western Atlantic DPS and 19
years for the eastern Atlantic/Mediterranean DPS. Mean generation time
was computed as the fecundity-weighted average age of the spawning
population at equilibrium in the absence of fishing, where the values
for the age at maturity and natural mortality rate associated with the
eastern and western DPSs were set to those used by the SCRS (and
average weight was used as a proxy for fecundity). The mean generation
time was similar for the two stocks because the younger age of maturity
assumed for the eastern stock (which would imply a younger generation
time) is mitigated by the lower natural mortality rate assumed for
spawning age fish (which implies an older generation time). The SRT
also reasoned that it will take a generation time to fully realize the
impacts of various management measures, and thus, determined that
approximately 17 to 19 years is a reasonable timeframe to define the
foreseeable future for Atlantic bluefin tuna. Further support for this
timeframe is provided in the 1998 rebuilding plan, as this was based on
a mean generation time of 20 years (K. Blankenbeker, 2010, Pers.
comm.). Additionally, projections through ICCAT have been estimated for
20 years for the western Atlantic. Because of ICCAT negotiations that
can result in changes to annual quotas, we cannot estimate abundance
beyond 20 years with any degree of confidence.
As described above, section 4(a)(1) of the ESA and NMFS
implementing regulations (50 CFR 424) state that we must determine
whether a species is endangered or threatened because of any one or a
combination of the following factors: (A) Current or threatened habitat
destruction or modification or curtailment of habitat or range; (B)
overutilization for commercial, recreational, scientific, or
educational purposes; (C) disease or predation; (D) inadequacy of
existing regulatory mechanisms; and (E) other natural or man-made
factors affecting the species' continued existence. This section
briefly summarizes the findings regarding these factors. Additional
details can be found in the SRR.
A. The Present or Threatened Destruction, Modification, or Curtailment
of Its Habitat or Range
The Gulf of Mexico is believed to possess certain features for
Atlantic bluefin tuna larval habitat which determine growth and
survival rates of Atlantic bluefin tuna and can be variable from year
to year (McGowan and Richards, 1989). The Gulf Stream can produce
upwelling of nutrient rich waters along the shelf edge, which may
provide an area favorable to maximum growth and retention of food for
the larvae (McGowan and Richards, 1989).
The Mediterranean Sea is a basin with unique characteristics, being
a semi-enclosed sea connected to the Atlantic Ocean through the narrow
Strait of Gibraltar, to the Red Sea by the man-made Suez Canal and to
the smaller enclosed Black Sea via the narrow Bosphorus Strait. The
Mediterranean Sea exchanges water, salt, heat, and other properties
with the North Atlantic Ocean, and is thus an important factor
affecting global water formation processes and variability, and
subsequently, the stability of the global thermohaline state of
equilibrium (Wurtz, 2010).
There are a variety of past, present, and reasonably foreseeable
future actions that have the potential to affect Atlantic bluefin tuna
habitat. They range, among other things, from coastal development and
associated coastal runoff and non-point source pollution in coastal
areas to outer continental shelf (OCS) oil and gas development, and
global climate change. Since most Atlantic bluefin tuna habitat is
comprised of open ocean environments occurring over broad geographic
ranges, large-scale impacts such as global climate change that affect
ocean temperatures, currents, and potentially food chain dynamics,
likely pose the greatest threat to Atlantic bluefin tuna habitat.
Anecdotal information suggests that such changes may be occurring and
influencing the distribution and habitat usage patterns of Atlantic
bluefin tuna as well as other highly migratory species (HMS) and non-
HMS fish stocks. Ocean
[[Page 31563]]
temperature changes of a few degrees can disrupt upwelling currents
that reduce or eliminate the nutrients necessary for phytoplankton and
thereby, could have potential repercussions throughout the food chain.
As a result, changes in migratory patterns may be the first indication
that large scale shifts in oceanic habitats may be occurring. Some have
pointed to the shift in availability of Atlantic bluefin tuna from
fishing grounds off North Carolina to waters off Canada during the
winter months as evidence of changes in oceanographic conditions that
may be affecting historical distribution patterns. Although the
evidence is still lacking, causative factors in the shift include
preferences for cooler water temperatures and prey availability. A
recent report by the Conservation Law Foundation indicated that low
food availability had reduced growth rates in larval cod and haddock
and that rising sea surface temperatures had the potential to further
reduce productivity for these and other fish stocks off the New England
coast (Bandura and Vucson, 2006).
Wetland loss is a cumulative impact that results from activities
related to coastal development: Residential and industrial
construction, dredging and dredge spoil placement, port development,
marinas and recreational boating, sewage treatment and disposal,
industrial wastewater and solid waste disposal, ocean disposal, marine
mining, and aquaculture. In the late 1970s and early 1980s, the United
States was losing wetlands at an estimated rate of 300,000 acres (1,214
sq km) per year. The Clean Water Act and state wetland protection
programs helped decrease wetland losses to 117,000 acres (473 sq km)
per year between 1985 and 1995. Estimates of wetlands loss vary
according to the different agencies. The U.S. Department of Agriculture
attributes 57 percent of wetland loss to development, 20 percent to
agriculture, 13 percent to deepwater habitat, and 10 percent to forest
land, rangeland, and other uses. Of the wetlands lost to uplands
between 1985 and 1995, the FWS estimates that 79 percent of wetlands
were lost to upland agriculture. Urban development and other types of
land use activities were responsible for 6 percent and 15 percent of
wetland loss, respectively.
Nutrient enrichment has become a major cumulative problem for many
coastal waters. Nutrient loading results from the individual activities
of coastal development, non-point source pollution, marinas and
recreational boating, sewage treatment and disposal, industrial
wastewater and solid waste disposal, ocean disposal, agriculture, and
aquaculture. Excess nutrients from land based activities accumulate in
the soil, pollute the atmosphere, pollute ground water, or move into
streams and coastal waters. Nutrient inputs are known to have a direct
effect on water quality. For example, in extreme conditions, excess
nutrients can stimulate excessive algal blooms or dinoflagellate growth
that can lead to increased turbidity, decreased dissolved oxygen, and
changes in community structure, a condition known as eutrophication.
In addition to the direct cumulative effects incurred by
development activities, inshore and coastal habitats are also
jeopardized by persistent increases in certain chemical discharges. The
combination of incremental losses of wetland habitat, changes in
hydrology, and nutrient and chemical inputs produced over time can be
extremely harmful to marine and estuarine biota, resulting in diseases
and declines in the abundance and quality of the affected resources.
One of the major activities with the potential to impact Atlantic
bluefin tuna habitat is oil and gas development on the OCS. Anecdotal
information suggests that some recreational fishermen may target
various fish species, including HMS, in the vicinity of oil platforms
due to increased abundance and availability near platforms. The
apparent increase in abundance of several species may be due to
increased prey availability resulting from various fish and
invertebrate communities that are attracted or attach directly to the
structures and submerged pilings. While the apparent increase in
abundance of fish near oil platforms may appear to be beneficial,
little is known about the long-term environmental impacts of changes
caused by these structures to fish communities, including potential
changes to migratory patterns, spawning behavior, and development of
early life stages. Currently, there is debate about whether the
positive effects of the structures in attracting fish communities would
be reduced by removal of the platforms when they are decommissioned.
As of 2009, there were approximately 4,000 oil and gas platforms in
the Gulf of Mexico and fewer than 100 in the Atlantic. Most of the
platforms were in waters shallower than 1,000 feet (305 m); however,
there are ongoing efforts to expand oil drilling to deeper areas of the
Gulf. Approximately 72 percent of the Gulf of Mexico's oil production
comes from wells drilled in 1,000 feet (305 m) of water or greater
(MMS, 2008(b)). Eight new deepwater discoveries were announced by oil
and gas operators in 2007, with the deepest in 7,400 ft (2,256 m) of
water (MMS, 2008(a)). Many of the shallower sites and most of the
deepwater sites fall within habitats used by HMS, particularly by
Atlantic bluefin tuna. Many of the deeper sites are also located within
the HAPC for Atlantic bluefin tuna.
In the Atlantic, ten oil and gas lease sales were held between 1976
and 1983. Fifty-one wells were drilled in the Atlantic OCS; five
Continental Offshore Stratigraphic Test wells between 1975 and 1979,
and 46 industry wells between 1977 and 1984. Five wells off New Jersey
had successful drillstem tests of natural gas and/or condensate. These
five wells were abandoned as non-commercial.
In addition to the oil and gas wells, several liquefied natural gas
(LNG) facilities have been proposed in the Gulf of Mexico. For LNG
facilities, a major environmental concern is the saltwater intake
system used to heat LNG and regasify it before piping it to shore. LNG
facilities sometimes have open loop, once through heating systems known
as open rack vaporizers, which require large amounts of sea water to
heat LNG. As described in a draft environmental impact statement (DEIS)
for an LNG project in the Gulf of Mexico, the use of the sea water
intake system would subject early life stages of marine species to
entrainment, impingement, thermal shock, and water chemistry changes,
potentially causing the annual mortality of hundreds of billions of
zooplankton, including fish and shellfish eggs and larvae. Depending on
the location of the facility, this could have an adverse effect on
habitat for Atlantic bluefin tuna or other HMS species. Closed loop
systems are currently being used in the United States to regasify LNG
and are proposed for multiple onshore and offshore LNG terminals
throughout the nation, with the notable exception of the offshore
waters of the Gulf of Mexico. These systems, which do not rely on an
external saltwater intake source, and thus, do not require large
amounts of seawater, have considerably lower impacts on fish eggs,
larvae, and zooplankton than open loop systems.
For oil platforms, there are direct and indirect impacts to the
environment such as disturbance created by the activity of drilling,
associated pollution from drilling activities, discharge of wastes
associated with offshore exploration and development, operational
wastes from drilling muds and cuttings, potential for oil spills, and
potential for catastrophic spills caused
[[Page 31564]]
by accidents, such as the Deepwater Horizon (DWH) oil spill in 2010
(described below), or hurricanes and alteration of food webs created by
the submerged portions of the oil platform, which attract various
invertebrate and fish communities.
The potential effect of the DWH oil spill on the future abundance
of western Atlantic bluefin tuna was evaluated by comparing the
projections made by the SCRS (SCRS, 2010) to similar projections that
assume the number of yearlings (1-year-old-fish) in 2011 will be
reduced by 20 percent. The 20 percent value was based on the recent
report by the European Space Agency that suggested 20% of the surface
was oiled. However, this value does not reflect subsurface oil
investigations and are ongoing on its potential distribution and
impacts.
The SRT noted that another study (SEFSC, 2011, pers. comm.)
suggested that considerably less than 20 percent of the spawning
habitat for the western Atlantic DPS was affected by the spill.
Moreover, if some larvae survived their encounter with oil and
associated toxicants, or if density dependent processes are involved in
the mortality of Atlantic bluefin tuna after the larval phase, then a
20 percent loss of spawning habitat might result in something less than
a 20 percent reduction in the expected number of yearlings. However,
factors such as the distribution of oil below the surface and the
advection of larvae into the spill area after spawning are not well
known. Accordingly, the SRT regarded 20 percent as a reasonable upper
bound for the mortality rate of Atlantic bluefin tuna larvae owing to
the spill event.
The effect of the DWH spill on bluefin tuna is an area of focus of
NOAA's Natural Resources Damage Assessment (NRDA) team. That team is
conducting targeted analyses on the effects of the spill on tuna, but
most of those analyses are not yet available. The SRT coordinated with
the NRDA team, and we have incorporated its information into the
decision making process. The NRDA scientists provided plots of the
paths of 12 satellite-tagged bluefin tuna that entered the Gulf of
Mexico between 2008 and 2010. The NRDA scientists also reported on the
progress of other work (e.g., physiological effect of toxicants), but
the work was not yet at a stage that could be considered by the SRT.
In summary, independent projections with two different types of
models show that a 20 percent reduction in the 2010 year-class will
likely result in less than a 4 percent reduction in future spawning
biomass. However, if a significant fraction of adult Atlantic bluefin
tuna were killed or rendered impotent by the spill, then subsequent
year-classes might also be reduced, leading to greater reductions in
SSB than estimated above. For example, if 20 percent of the adults were
also killed in 2010, then the SSB would be immediately reduced by 20
percent, which might lead to additional reductions in the 2011 and
subsequent year-classes (relative to what they would have been in the
absence of the spill). The reduction in the 2010, 2011, and subsequent
year classes would, in turn, lead to reductions in future SSB levels (9
years later as they begin to mature). To date, however, there is no
evidence to suggest that any portion of adults were immediately
affected although studies are ongoing that may give more information on
possible long term impacts. The results from several electronic tagging
studies confirm that some Atlantic bluefin tuna have historically spent
at least a portion of their time in the waters in the vicinity of the
spill area, but the exact fraction is difficult to quantify because of
the uncertainties associated with inferring tracks and the rather low
number of samples. All of the electronically-tagged bluefin tuna that
were known to have spent time in the Gulf of Mexico during the actual
spill event (8 fish) survived long after leaving the Gulf of Mexico.
Given that it is not possible to determine the level of impact on
adults from the DWH oil spill at this time, scientists at the SEFSC re-
ran the extinction risk models assuming spill-induced mortality rates
of 20 percent for larvae and from 5 to 50 percent for adults. The
short-term (10 year) risk of extinction was negligible for all levels
of mortality examined. The long-term risk (e.g., projected to 2100) did
not exceed 5 percent except under the high recruitment scenario when
adult mortality rates exceeded 15 percent. Using the latest
information, including the 2010 larval survey, SEFSC scientists
developed a worst-case scenario for larval mortality of 15 percent
(their best estimate was about 7 percent). Accordingly, adult mortality
rates of 15 percent also represent a worst-case scenario because it
implies the same proportion of adults encountered oil as the larvae and
that all of those ``oiled'' adults subsequently died. Thus, it appears
that adult mortality rates would have to be extremely high in order to
incur a substantial risk of extinction.
Because the information on larval and adult mortality from the DWH
oil spill is not certain, NOAA used the best available science to model
``worst case scenarios.'' From these model projections, we were able to
determine that although it is not possible to accurately determine the
level of effect at this time, even if the oil spill had the highest
level of effect currently viewed as scientifically plausible, the
species would not warrant listing at this time. While we cannot wait
for the targeted analyses being conducted in the NRDA process, we
intend to revisit this decision no later than 2013 once the NRDA
analyses have been concluded to determine whether the DWH oil spill
altered the condition of the species. Additionally, new stock
assessments will be conducted for bluefin tuna in 2012 and will be
available in the fall, and new compliance reports will be available
from ICCAT. Thus, this information will be considered as well.
Summary and Evaluation of Factor A
Currently, there are numerous potential coastal habitat threats as
identified above (e.g., dredging, mining, navigation); however, the
ones of most significance for Atlantic bluefin tuna are offshore (e.g.,
petroleum, LNG). While these could represent potential future threats
to the species, at this time, these activities are not negatively
affecting Atlantic bluefin tuna, and the SRT concluded, and we concur
that they do not represent a substantial risk to the long-term
persistence of the species. In the future, should offshore effects such
as petroleum and LNG be proposed, the EFH and HAPC process would
provide a mechanism by which those impacts could be addressed.
B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
Fishing for Atlantic bluefin tuna has occurred in the Mediterranean
since the 7th millennium BC (Desse and Desse-Berset, 1994, in Fromentin
and Powers, 2005). According to Fromentin and Ravier (2005) and Porch
(2005), the development of the sushi-sashimi market during the 1980s
made fishing for Atlantic bluefin tuna significantly more profitable
than it was in earlier times, and this resulted in a considerable
increase in the efficiency and capacity of fisheries during this time.
The increased profitability associated with these new technologies
resulted in the rapid development of new and powerful fleets in the
Mediterranean countries, and the expansion of effort which exploited
fish in the Mediterranean and North Atlantic Japanese longline
fisheries also expanded in the Central North Atlantic, adding pressure
on Atlantic bluefin tuna stocks (Fromentin and Powers, 2005).
[[Page 31565]]
The development and redistribution of all the fisheries resulted in
rapid increases in yields since the 1980s, especially in the
Mediterranean Sea. Eastern Atlantic and Mediterranean catches reached
an historical peak of over 50,000 mt during the mid-1990s. Catches in
the West Atlantic, including discards, have been relatively stable
since the imposition of quotas in 1982. However, total western Atlantic
catch declined steadily from the high of 2002 until 2007, primarily due
to considerable reductions in catches by U.S. fisheries. Two plausible
explanations for this situation were considered by the SCRS: (1)
Availability of fish to the U.S. fishery was abnormally low, and/or (2)
the overall size of the population in the western Atlantic declined
substantially from the levels of recent years. SCRS noted in its 2010
stock assessment report that there is no overwhelming evidence to favor
one explanation over the other but that the base case assessment
implicitly favors the idea of changes in regional availability by
virtue of the estimated increase in SSB. The decrease indicated by the
U.S. catch rate of large fish was matched by the increase in several
other large fish indices. In 2009, the United States harvested its
national base quota.
In U.S. fisheries, bluefin tuna are caught with purse seines,
handgear (rod and reel, handline, and harpoon), and pelagic longlines.
As of October 2010, there were over 32,000 permitted vessels that may
participate in the Atlantic tuna fisheries (NMFS, 2010). All owners/
operators of vessels (commercial, charter/headboat, or recreational)
fishing for regulated Atlantic tunas (Atlantic bluefin, bigeye,
albacore, yellowfin and skipjack tunas) in the management area must
obtain an Atlantic tunas permit or an Atlantic HMS vessel permit.
Commercial categories are monitored by a census of landing cards,
whereas the recreational catch is monitored primarily by a survey,
although the states of Maryland and North Carolina have implemented
recreational census bluefin tuna tagging programs as well. Commercial
fisheries are focused on `large medium' (73 in (185 cm) to less than 81
in (206 cm) curved fork length (CFL)) and `giant' (81 in (206 cm) CFL
or greater) Atlantic bluefin tuna, while recreational fisheries are
focused on `large school/small medium' Atlantic bluefin tuna (47 in
(119 cm) to less than 73 in (185 cm) CFL), with allowances for `school'
(27 in (68 cm) to less than 47 in (119 cm) CFL), `large medium', and
`giant' Atlantic bluefin tuna. Recreational fisheries are carried out
by private vessels fishing in the Angling category, and vessels for
hire fishing under the Charter/Headboat category.
There are numerous scientific studies on Atlantic bluefin tuna, the
largest of which is being coordinated by ICCAT's SCRS--the Atlantic
wide Grande Bluefin Tuna Year Program (GBYP). It has multiple
objectives, including improving the understanding of key biological and
ecological processes, basic data collection (including information from
farms, observers, and VMS), provision of scientific advice on stock
status through improved modeling of key biological processes (including
growth and stock-recruitment and mixing between various areas), and
developing and using biologically realistic operating models for more
rigorous management option testing. Research undertaken to date through
the ICCAT program, or in coordination with it by scientists from
ICCAT's membership, has been either non-lethal (i.e., aerial surveys)
or has been intended to be non-lethal (i.e., tagging programs),
although mortalities, while minimal, do sometimes occur after a tagging
event.
Other types of research (i.e., microconstituent analysis,
organochlorine tracer analysis, genetic analysis) primarily rely on
samples taken from fish harvested in commercial fishing operations or
from historical collections. Larval surveys, such as those conducted by
the United States, and activities to monitor YOY do harvest Atlantic
bluefin tuna specifically for research purposes, but the mortality
caused by these activities is low. With respect to collections for
education, this activity is minor and relies largely on products
obtained from other activities, such as commercial fishing. Where it
does cause Atlantic bluefin tuna mortalities directly, such as the
collection of YOY, it is minor. Furthermore, there was no information
to suggest that a substantial live aquarium trade in Atlantic bluefin
tuna exists.
Summary and Evaluation of Factor B
Current impacts from commercial, recreational, scientific or
educational purposes do not represent a substantial risk to the long-
term persistence of the species. Atlantic bluefin tuna fisheries are
closely managed by various regulatory mechanisms, and current TAC
levels are projected to result in increased population levels of the
DPSs as long as there is a high degree of compliance. In addition,
scientific collections or collections for educational purposes
described above do not seem to be significantly affecting the status of
Atlantic bluefin tuna, and are not likely to significantly affect the
long-term persistence of Atlantic bluefin tuna now or into the future.
C. Predation and Disease
As large apex predators, Atlantic bluefin tuna are not heavily
preyed upon. However, predators such as killer whales (Orcinus orca)
and pilot whales (Globicephala spp.), and several shark species such as
white sharks (Carcharodon carcharias), shortfin mako (Isurus
oxyrinchus), and longfin mako (Isurus paucus) (Nortarbartolo di Sciara,
1987; Collette and Klein-MacPhee, 2002; de Stephanis, 2004; Fromentin
and Powers, 2005) may prey on Atlantic bluefin tuna. Juvenile Atlantic
bluefin tuna may also be preyed upon by bluefish (Pomatomus saltatrix)
and seabirds (Fishwatch, NMFS, 2010).
Little information exists on diseases in Atlantic bluefin tuna.
Most of the available disease information for this species, Pacific
bluefin tuna (Thunnus orientalis), and southern bluefin tuna (Thunnus
maccoyii) comes from studies on fish reared in net pens prior to
harvesting for the market (Munday et al., 2003; Bullard et al., 2004;
Oraic and Zrncic, 2005; Mladineo et al., 2006; Hayward et al., 2007).
Peric (2002) reported lesions consistent with pasteurellosis
(Photobacterium damsel piscicida) after examining carcasses of 25
harvested Atlantic bluefin tuna. Lesions were similar to those seen in
sparids with chronic pasteurellosis. As the causative organism,
pasteurellosis does not survive for long outside the host, and
prevalence is reported to be very low in Atlantic bluefin tuna (Munday
et al., 2003). However, high mortalities of Atlantic bluefin tuna
reared in Adriatic Sea cages occurred during winter 2003 and spring
2004. Based on the results of bacteriological, serological, and
histological analysis, Mladineo et al. (2006) concluded that
pasteurellosis was the causative agent of the mortalities, which was
the first outbreak of this kind in reared tuna. Putative tuberculosis
was reported in a single specimen of Atlantic bluefin tuna (Biavati and
Manera, 1991, as reported by Munday et al., 2003), but the cause is
unknown.
Summary and Evaluation for Factor C
Adult Atlantic bluefin tuna are not likely affected to any large
degree by predation by large whales and other large predators, nor are
they likely to be affected to any large degree by diseases caused by
viruses, bacteria, protozoans, metazoans, or microalgae. Most of the
[[Page 31566]]
information on diseases in tunas comes from studies on cultured tuna,
and the culture environment introduces stresses to the fish; therefore,
even if studies indicated that cultured Atlantic bluefin tuna were
highly susceptible to diseases and suffered high mortality rates, it is
not possible to infer from these data that wild Atlantic bluefin tuna
experience the same diseases and mortality rates. The best available
scientific and commercial information indicates that threats to
Atlantic bluefin tuna from predation and disease do not significantly
affect the long-term persistence of Atlantic bluefin tuna now or into
the future.
D. Existing Regulatory Authorities, Laws and Policies
Since 1982, Atlantic bluefin tuna have been separated into two
management units or stocks (western Atlantic and eastern Atlantic/
Mediterranean), which coincide with the two DPSs identified in the SRR.
ICCAT has established various conservation and management measures for
both stocks over the years, most often in those years where new stock
assessments have been completed by SCRS, as these inform management
decisions. ICCAT, however, is free to adopt or alter conservation and
management measures even in years where no new stock assessment has
been conducted, and it has occasionally done so. In addition to the
stock assessment meetings (which have been held recently about every 2
years), the SCRS reports on fishery trends each year. These metrics can
include catch, effort and size trends, as well as updated abundance
indices (such as standardized catch rate trends by age category and
larval survey results), and trends can provide information on threats
to the stock even during non-assessment years.
In light of the connection between the two stocks and fisheries,
SCRS has advised that robust management is needed for both stocks to
ensure effective conservation. Recognizing that management could
potentially benefit from an improved understanding of bluefin tuna
stock structure and mixing, ICCAT and its members have taken a number
of steps to improve information in this area. Pending the outcome of
ongoing research on stock structure and mixing, ICCAT has actively
looked at management strategies that can take better account of mixing.
In that regard, ICCAT has had a measure in place intended to limit
catches in the central North Atlantic, an area with high mixing rates,
since 2003. Catches from this area are now significantly reduced from
previous levels. In addition, ICCAT has adopted the requirement that
parties cannot shift effort across the 45 degree management boundary
separating the two stocks of bluefin tuna.
The western Atlantic bluefin tuna fishery in the United States is
managed under the dual authority of the Magnuson-Stevens Fishery
Conservation and Management Act (Magnuson-Stevens Act) and the Atlantic
Tunas Convention Act (ATCA). ATCA authorizes the Secretary of Commerce
to implement the binding recommendations of ICCAT. As the United States
implements legislation for ICCAT, ATCA also requires that the United
States implement binding recommendations adopted by that organization,
as necessary and appropriate; stipulates that the United States may not
promulgate a regulation that has the effect of increasing or decreasing
any allocation or quota of fish or fishing mortality allocated by
ICCAT; and establishes a number of procedural requirements.
At the 2010 ICCAT meeting, a measure was adopted for the western
Atlantic stock that, among other things, reduced the TAC from 1,800 t
(1,632.93 mt) to 1,750 t (1,587.57 mt) for both the 2011 and 2012
fishing seasons--a 2.8-percent reduction overall. Under the low
recruitment potential scenario, the new TAC has a 99-percent
probability of maintaining the fishing mortality of western Atlantic
bluefin tuna below the fishing mortality associated with MSY and a 95-
percent probability of maintaining the stock above the biomass that
will support MSY through the end of the rebuilding period. Combining
the results of the high and low recruitment potential scenarios, the
TAC has a 54-percent probability of ending overfishing within 2 years
and a 48-percent probability of rebuilding the stock to the
Bmsy level by the end of the rebuilding period. Under the
high recruitment potential scenario, the TAC has an 8-percent
probability of ending overfishing within 2 years and a zero-percent
chance of rebuilding the stock to the Bmsy level by the end
of the rebuilding period. It is important to note that, under any
scenario, the agreed TAC is expected to support continued stock growth
if compliance with agreed rules remains strong. For the western
Atlantic bluefin tuna fishery, compliance with ICCAT measures has
typically been high.
In addition to a new TAC, the measure includes an emergency clause
similar to the one added in 2009 to the eastern Atlantic/Mediterranean
bluefin tuna recommendation. It specified that if SCRS detects a
serious threat of stock collapse, ICCAT shall suspend all Atlantic
bluefin tuna fisheries in the western Atlantic for the following year.
The recommendation further calls on ICCAT members to contribute to
ICCAT's Atlantic-wide Bluefin Tuna Research Program, including the
enhancement of biological sampling. Consistent with past practice, the
provisions contained in previous conservation and management
recommendations were retained, including the prohibition on directed
fishing for Atlantic bluefin tuna in the Gulf of Mexico and minimum
size requirements.
Finally, the measure includes a request to SCRS to provide
additional information in the future that might be helpful to
management--including with respect to spawning grounds and the size
selectivity of the fishery. The next western Atlantic bluefin tuna
stock assessment is scheduled for 2012, and management measures will be
reconsidered at that time, taking into consideration the scientific
advice provided by SCRS.
During its 2010 annual meeting, ICCAT adopted a new recommendation
for eastern and Mediterranean Atlantic bluefin tuna. The TAC for 2011
and beyond (until changed) was set at 12,900 t (11,702.68 mt), 4.4-
percent reduction from the 2010 level of 13,500 t (12,246.99 mt). This
reduction is in addition to existing quota paybacks for previous
overharvests by the European Union and Tunisia. Thus, the adjusted
allowable catch for 2011 and 2012 is approximately 11,500 t (10,432.62
mt). Before taking into account these required reductions, the new TAC
has at least a 95-percent probability that the condition of the stock
will improve in the coming years and a 67-percent probability of
rebuilding the stock by 2023, the end of the rebuilding period.
Summary and Evaluation for Factor D
Western Atlantic bluefin tuna are highly regulated with TAC limits
generally set within the range recommended by SCRS. Greater reductions
in TAC for the eastern stock were discussed to account more fully for
the assessment uncertainties and to increase the probability and rate
of stock growth and recovery. For both eastern and western bluefin tuna
DPSs, catch levels agreed to in 2010 are expected to support continued
growth and recovery of the stocks if compliance with agreed rules
continues. Given the mixing between the stocks, improved stock
conservation in the east can be expected to benefit the western stock
as well. Based on the information above, the SRT concluded that the
existing
[[Page 31567]]
regulatory mechanisms if adequately enforced are sufficiently
protective of Atlantic bluefin tuna now and into the future, and we
concur with this conclusion.
E. Other Natural or Manmade Factors Affecting the Continued Existence
of the Species
The SRT examined other natural or manmade factors affecting the
continued existence of Atlantic bluefin tuna. Spatial distribution and
movement of Atlantic bluefin tuna were previously hypothesized to be
controlled by preferential ranges of temperature (ICCAT, 2006-2009);
but more recently, scientists hypothesized that juveniles and adults
are associated with ocean fronts, likely for purposes of foraging for
prey (Humston et al., 2001; ICCAT, 2006-2009). However, the complexity
of Atlantic bluefin tuna distribution and behavior is unlikely to be
explained by association with these fronts alone (Shick et al., 2004;
Royer et al., 2004). Because of the relationship of Atlantic bluefin
tuna to sea surface temperature, the SRT considered the impact of
climate change to Atlantic bluefin tuna.
Research studies have shown that migration and movement patterns
vary considerably between individuals, years, and areas (Lutcavage et
al., 1999; Block et al., 2001; De Metrio et al., 2004; ICCAT, 2006-
2009). The appearance and disappearance of past fisheries (e.g., Brazil
during the 1960s) could be a result of changes in spatial distribution
and/or migration (Fromentin and Powers, 2005; Fromentin, 2009).
Rijnsdorp et al. (2009) hypothesized a shift in distribution in
response to increased temperature associated with climate change, and
similar distribution shifts for other species have also been observed
(Nye et al., 2009). However, without a better understanding of the
processes that determine Atlantic bluefin tuna distribution, it is
difficult to project a response of the species to climate change.
Rijnsdorp et al. (2009) further hypothesized that if the habitat
for a certain life-history stage is spatially restricted (e.g.,
spawning), the species may be more sensitive to climate change. We
designated an HAPC for bluefin tuna spawning in the Gulf of Mexico in
Amendment 1 to the U.S. Consolidated HMS Fishery Management Plan (NMFS,
2009). This area is the primary spawning habitat for the western stock
of Atlantic bluefin tuna, although the potential for other spawning
locations has also been suggested (Galuardi et al., 2010). Climate-
induced temperature increases could increase stress for Atlantic
bluefin tuna during spawning in the Gulf of Mexico. Average ambient
temperatures measured during bluefin spawning activity ranged from 23.5
to 27.3 [deg]C (Teo et al., 2007). Atlantic bluefin tuna have been
found to withstand temperatures ranging from 3 to 30 [deg]C (Block et
al., 2001).
Although Atlantic bluefin tuna are believed to use deep diving to
thermoregulate, spawning behavior may preclude thermoregulation
behavior (Teo et al., 2007). Block et al. (2005) indicated that thermal
stress appeared to be contributing to mortality of pelagic longline-
caught Atlantic bluefin tuna on the Gulf of Mexico spawning grounds. If
increases in ocean temperature will mirror those forecasted for air
temperature by the Intergovernmental Panel on Climate Change (IPCC)
(2007) (i.e., + 0.20 [deg]C per decade), and add ten decade's worth of
temperature increase (i.e., a total of 2.0 [deg]C) to the temperatures
reported by Teo et al. (2007), then Gulf of Mexico temperatures during
Atlantic bluefin tuna spawning season could be estimated to reach 25.5
to 29.3 [deg]C by the turn of the century. Muhling et al. (2011)
modeled a variety of climate change simulations in the Gulf of Mexico
to quantify potential effects of warming on the suitability of the Gulf
of Mexico as a spawning ground for Atlantic bluefin tuna. Model results
showed that Atlantic bluefin tuna were indeed vulnerable to climate
change impacts, with increasing water temperature affecting both
spawning times and locations, as well as larval growth, feeding and
survival (Muhling et al., 2011). Furthermore, if ambient values of
abiotic factors such as salinity or pH exceed the tolerance limits for
planktonic Atlantic bluefin tuna eggs and larvae, these life stages
could be negatively affected physiologically.
Fabry et al. (2008) reviewed the potential impacts of ocean
acidification on marine fauna and ecosystem processes. The information
reviewed indicated that marine fish were physiologically highly
tolerant of carbon dioxide. Ishimatsu et al. (2004) found that
hatchling stages of some species appeared fairly sensitive to pH
decreases on the order of 0.5 or more, but high carbon dioxide
tolerance developed within a few days of hatching.
Indirect trophic level dynamics may have some impact to Atlantic
bluefin tuna as a result of climate change and ocean acidification.
Acidification could lead to dissolution of shallow-water carbonate
sediments and could affect marine calcifying organisms, including
pteropods, an important component of the plankton in many marine
ecosystems (Orr et al., 2005). In their review article, Walther et al.
(2002) stated that indirect impacts on marine systems appear to be the
most widespread effects of climate change. For example, the persistence
of a positive vector for the North Atlantic Oscillation (NAO) modifies
marine primary and secondary production (Fromentin and Planque, 1996),
which could in turn affect the availability of planktonic food for fish
larvae and recruitment success (Cushing, 1990). However, ICCAT
scientists analyzed the association of the NAO with eastern Atlantic
bluefin tuna recruitment and found no relationship (ICCAT, 2002).
Availability of nutrients could also be affected by changes in
carbon dioxide, which could affect primary production, changes in
species composition, and higher trophic levels (Fabry et al., 2008).
Kimura (2010) modeled a combination of environmental factors when
considering the impact to the recruitment of juvenile Pacific bluefin
tuna. For example, an increase in ocean temperature would speed the
transport of larvae in the Kuroshio current, causing the larvae to
arrive too quickly to cold coastal waters. When coupled with high
temperatures exceeding the optimal range on the spawning grounds,
larval recruitment was predicted in 2010 to decline to 36 percent of
present recruitment levels (Kimura et al., 2010). In addition, a long-
lived species such as Atlantic bluefin tuna could have less
evolutionary ability to adapt to climate change than shorter-lived
species.
Chase (2002) identified squid as one of several important food
sources for Atlantic bluefin tuna caught off New England. Epipelagic
squid (e.g., Illex and Loligo sp.) have been found to be highly
sensitive to carbon dioxide because of their unique physiology (Portner
et al., 2004; Seibel, 2007). Yamada and Ikeda (1999) found increased
mortality for certain arthropod plankton (krill and certain copepods)
with increasing exposure time and decreasing pH. Larval Thunnus sp.
have been found to feed primarily on copepods (Catalan et al., 2007;
Llopiz and Cowen, 2009). As pelagic predators, Atlantic bluefin tuna
are considered opportunistic, and loss of one food source may not have
negative consequences. However, in the Florida straits, larval Thunnus
sp. appeared to exhibit selective feeding behavior (Llopiz and Cowen,
2009) and thus, larvae may not be as opportunistic in feeding as adult
Atlantic bluefin tuna are.
Offshore aquaculture was identified as a potential threat to
Atlantic bluefin
[[Page 31568]]
tuna by the SRT. Potential impacts resulting from offshore aquaculture
could include increased nutrient loading, habitat degradation, fish
escapement, competition with wild stocks, entanglement of endangered or
threatened species and migratory birds, spread of pathogens, user
conflicts, economic and social impacts on domestic fisheries, and
navigational hazards (GMFMC, 2009); however, there is no information to
indicate that offshore aquaculture is impacting Atlantic bluefin tuna.
The most recent available information indicated that there are no
finfish offshore aquaculture operations in U.S. Federal waters.
According to the Gulf of Mexico Fishery Management Council (GMFMC) FMP
for offshore aquaculture in the Gulf of Mexico, marine aquaculture
would be prohibited in Gulf of Mexico EEZ HAPCs, marine reserves,
marine protected areas, Special Management Zones, permitted artificial
reef areas, and coral reef areas as defined and specified in 50 CFR 622
(GMFMC, 2009). In addition, areas where marine aquaculture is
prohibited in the Gulf of Mexico overlap with the spawning areas of the
western Atlantic DPS, and thus, the SRT did not expect any impacts to
the spawning habitat of the DPS from offshore aquaculture. The SRT was
not aware of specific information pertaining to the effects of offshore
aquaculture on the habitat in the eastern Atlantic/Mediterranean;
however, impacts to the DPS may be similar to the potential impact
resulting from offshore aquaculture as noted above.
Summary and Evaluation of Factor E
The SRT considered all other natural or manmade factors that may
affect the DPSs, including climate change impacts, ocean acidification,
and aquaculture/enhancement. The SRT identified several potential
natural or manmade threats to Atlantic bluefin tuna, and while these
could represent potential future threats to the species, at this time,
the SRT determined that current and future impacts are not likely and
do not represent a substantial risk to the long-term persistence of
either DPS. We concur with this conclusion.
Current and Future Protective Efforts
In February 2011, a special meeting of ICCAT's Compliance Committee
(COC) was held. The purpose was to reinforce the commitment of all
parties to implement the eastern Atlantic bluefin tuna recommendation
from the start of the 2011 season and, toward that end, to review the
implementation plans (which included fishery management, inspection,
and capacity reduction aspects) of eastern Atlantic bluefin tuna
harvesters with a view to endorsing those plans in advance of the
season.
In addition to taking action on the implementation plans, the COC
adopted an allocation table specifying the allowable harvest limits by
ICCAT members, which included all adjustments, and a fleet capacity
table reflecting required reductions for 2011. Given input from those
present at the COC intersessional, the adjusted TAC of 11,502.89 t
(10,435.25 mt) should be the upper bound of realized catches. Factoring
in that a few countries have indicated they will not be fishing and
their combined quota level is 364.33 t (330.51 mt), actual catches may
be more on the order of 11,138.56 t (10,104.73 mt)--notwithstanding any
action by ICCAT to suspend one or more fisheries in 2011 due to lack of
implementation plan endorsement. Any additional reductions in catch
will increase the probability of rebuilding the stock by 2023.
In addition, the 2010 eastern Atlantic bluefin tuna recommendation
also strengthened the monitoring and control scheme, including enhanced
monitoring of farming operations, further restrictions on joint fishing
operations (e.g., generally prohibiting joint operations between
contracting parties and clarifying that each party is responsible and
accountable for catches made under such operations), and requiring
fishing capacity issues to be fully addressed by 2013.
Western Atlantic bluefin tuna harvesters are expected to fully
implement Recommendation 10-03 by mid-June 2011. This will involve
reduced quotas for the United States, Canada, and Japan for 2011 and
2012. In addition, NMFS has published a proposed rule to implement the
ICCAT recommended U.S. base quota, distributing the quota among
domestic quota categories consistent with the 2006 Consolidated HMS
Fishery Management Plan, and to adjust the 2011 U.S. quota and
subquotas to account for Atlantic bluefin tuna dead discards and
unharvested 2010 quota allowed by ICCAT to be carried forward to 2011
(76 FR 13583). Furthermore, NMFS monitors the Atlantic bluefin tuna
fishery and has the authority to take in-season actions such as fishery
closures and retention limit adjustments to ensure available quotas are
not exceeded or to enhance scientific data collection from, and fishing
opportunities in, all geographic areas.
Effective May 5, 2011, NMFS requires the use of ``weak hooks'' by
pelagic longline vessels fishing in the Gulf of Mexico. A weak hook is
a circle hook that meets NMFS' current size and offset restrictions but
is constructed of round wire stock that is thinner-gauge (i.e., no
larger than 3.65 mm in diameter) than the 16/0 circle hooks currently
used in the Gulf of Mexico pelagic longline fishery. The purpose of the
proposed action is to reduce pelagic longline incidental catch of
bluefin tuna in the Gulf of Mexico, which is the known spawning area
for the western Atlantic DPS of bluefin tuna (as described above). The
action is intended to increase Atlantic bluefin tuna spawning potential
and subsequent recruitment into the fishery, and could also potentially
reduce negative ecological and fishing impacts on non-target or
protected species.
Listing Determination
Long-term (2010-2100) projections of abundance of the two Atlantic
bluefin tuna DPSs (western Atlantic and eastern Atlantic/Mediterranean)
were conducted by the SRT using the protocols adopted by the ICCAT SCRS
(SCRS, 2010). We have determined that a 5-percent probability of
extinction in 20 years is a reasonable threshold for endangered status.
The probability of extinction was projected by the SRT to be near zero
for both DPSs over the 5 to 10-year horizon normally examined by the
SCRS, even for catch quotas that are much larger than allowed under the
current ICCAT management regulations. Even after 20 years, the
probability of extinction does not exceed 5 percent unless the level of
sustained catch after 2010 is 3,000 mt or more for the western Atlantic
DPS, and 40,000 mt or more for the eastern Atlantic/Mediterranean DPS
(the 2011 TACs for the western Atlantic and eastern Atlantic/
Mediterranean DPSs are 1,750 t (1,587.57 mt) and 12,900 t (11,702.68
mt) respectively, with the adjusted quota for the eastern fishery being
below 11,599 t (10,522.44 mt) in 2011 and 2012.
Several authors have suggested that populations with fewer than 500
individuals are doomed to eventual extinction due to the loss of
genetic diversity (Franklin, 1980; Soule, 1980). Matsuda et al. (1998)
used 500 mature animals as the threshold for their extinction risk
assessment of southern bluefin tuna. In order to address the potential
for quasi-extinction, the SRT performed a second set of analyses with
the extinction threshold set at 500 spawners, rather than 2 spawners
(see Tables 1 and 2 below for the results with 500 spawners and section
9.1.3 of the status review report for the tables with the results for 2
spawners).
[[Page 31569]]
Table 1--Forecasted Probability That Fewer Than 500 Adult Bluefin Tuna Will Survive in the East Atlantic and Mediterranean Sea by Year and Catch Level
(All 24 Scenarios Combined). Current Management Recommendations Under ICCAT Specify a Total Allowable Catch of 12,900 mt
[In percent]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Catch (mt) 2010 2011 2020 2030 2040 2050 2060 2100
--------------------------------------------------------------------------------------------------------------------------------------------------------
0............................................... 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
5,000........................................... 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
10,000.......................................... 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
12,900.......................................... 0.0 0.0 0.0 0.0 0.1 0.1 0.2 0.2
17,000.......................................... 0.0 0.0 0.0 0.2 0.7 1.2 1.4 1.5
20,000.......................................... 0.0 0.0 0.0 0.6 2.6 3.5 3.9 4.2
25,000.......................................... 0.0 0.0 0.0 3.4 8.7 11.2 12.3 13.2
30,000.......................................... 0.0 0.0 0.0 8.5 19.0 25.1 28.8 34.8
40,000.......................................... 0.0 0.0 0.2 25.9 45.9 51.5 54.0 57.6
50,000.......................................... 0.0 0.0 0.9 46.1 63.0 66.4 67.2 67.8
60,000.......................................... 0.0 0.0 2.1 59.9 70.6 72.0 72.5 72.8
70,000.......................................... 0.0 0.0 3.7 67.9 77.7 81.5 83.1 85.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Table 2--Forecasted Probability That Fewer Than 500 Adult Bluefin Tuna Will Survive in the West Atlantic by Year and Catch Level (Assuming the High and
Low Recruitment Scenarios Are Equally Plausible). Current Management Recommendations Under ICCAT Specify a Total Allowable Catch of 1,750 mt
[In Percent]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Catch (mt) 2010 2011 2020 2030 2040 2050 2060 2100
---------------------------------------------------------------------------------------------------------------------------------------------
0.................................... 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
1,000................................ 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
1,250................................ 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.1
1,500................................ 0.0 0.0 0.0 0.0 0.2 0.5 0.6 0.7
1,750................................ 0.0 0.0 0.0 0.3 0.8 1.5 1.9 2.3
2,000................................ 0.0 0.0 0.0 1.0 3.1 3.9 5.0 5.4
2,250................................ 0.0 0.0 0.0 2.9 7.4 10.5 12.8 14.9
2,500................................ 0.0 0.0 0.3 5.9 16.7 23.0 26.2 29.8
2,750................................ 0.0 0.0 0.5 11.8 30.3 39.4 45.2 55.1
3,000................................ 0.0 0.0 1.1 21.9 46.2 58.9 67.4 79.3
3,500................................ 0.0 0.0 3.1 49.8 78.6 88.8 93.4 95.4
4,000................................ 0.0 0.0 8.7 76.7 95.9 97.6 98.6 98.9
5,000................................ 0.0 0.0 35.4 97.7 99.7 99.9 99.9 99.9
--------------------------------------------------------------------------------------------------------------------------------------------------------
The SRT determined that the probability of extinction increases
substantially over the long term, due to inherent uncertainties in the
assumptions made for long-term projections; however, even with these
uncertainties, the risk still remains quite low for the catch levels
permitted under current management even when projected out to 2100
(about 2-percent probability for the western DPS and less than 1
percent for the eastern DPS). The level of extinction risk was found to
be only slightly higher when the threshold for extinction was set to
500 spawners rather than 2 spawners and projected out to 2100 (2.3-
percent probability for the western DPS, and 0.2-percent probability
for the eastern DPS). However, given the high inherent uncertainties in
long-term projections, projections made out to 2100 cannot reliably
estimate a probable risk of extinction.
One important source of uncertainty not considered in the above
projections was the nature of intermixing between the eastern and
western DPSs. Two-stock virtual population analyses used by SCRS (2008)
to estimate the level of mixing from stock composition (otolith
microcontituent) data produced estimates of spawning biomass that were
similar to the levels estimated without mixing. However, similar models
that estimated mixing from tagging data produced estimates of spawning
biomass that were generally higher than the models without mixing,
particularly for recent years. If spawning biomass is higher than
estimated by the base (no-mixing) models, then the short-term
extinction risk may be lower than suggested in the analyses above by
virtue of the fact that any given catch level will amount to a lower
percentage of the adult population. This is especially true for the
western DPS where the effect of estimating mixing is most profound as
discussed above. The long-term implications for extinction risk are
less clear as they would involve changes in the estimated productivity
of the two stocks, which have not yet been evaluated. It should be
noted, however, that ICCAT (2008) considered their analyses of mixing
as not reliable enough to be used as the basis for management advice
because both the tagging and stock composition data were regarded as
incomplete in the sense that they did not represent random samples of
the overall Atlantic bluefin tuna population.
Another important source of uncertainty not addressed in the
extinction risk analysis is the possible effect of adult mortality from
the DWH oil spill. As noted previously, there is no evidence of adult
mortality; however, it is still possible some adult mortality or impact
to reproductive capacity occurred. Because the information on larval
and adult mortality from the
[[Page 31570]]
DWH oil spill is not certain, NOAA used the best available science to
model ``worst case scenarios.'' From these model projections, it was
possible to determine that if the oil spill had the highest level of
effect currently viewed as scientifically plausible (e.g., 15 percent
mortality), the species would not warrant listing at this time.
In summary, the projections presented in the SRR suggest that the
probability of extinction of either DPS is negligible within the
generation time of both DPSs (generation time is equivalent to 17 to 19
years) unless the catches were nearly doubled over those allowed by
current regulations. The long-term projections out to 2100 indicate
that if rigorously enforced, current regulations are sufficient to
avoid a significant probability of extinction (greater than 5 percent),
but suggest a risk of extinction if management were to abandon the
existing rebuilding plans in favor of substantially higher catches or
if compliance is insufficient.
As mentioned above, the ESA defines an endangered species as any
species in danger of extinction throughout all or a significant portion
of its range, and a threatened species as any species likely to become
an endangered species within the foreseeable future throughout all or a
significant portion of its range. Section 4(b)(1) of the ESA requires
that the listing determination be based solely on the best scientific
and commercial data available, after conducting a review of the status
of the species and after taking into account those efforts, if any,
that are being made to protect such species. As stated previously, we
have concluded that there are two DPSs of Atlantic bluefin tuna. We
have considered the available information on the abundance of Atlantic
bluefin tuna from both DPSs, and whether any one or a combination of
the five ESA section 4(a)(1) factors significantly affect the long-term
persistence of Atlantic bluefin tuna now or into the foreseeable
future. We have reviewed the SRR, the high and low recruitment
potential projections, the CIE reviewers' comments, and other available
literature, and consulted with scientists, fishermen, and fishery
resource managers familiar with Atlantic bluefin tuna and related
research areas. After reviewing this information, we have determined
that listing the eastern Atlantic/Mediterranean and western Atlantic
bluefin tuna DPSs as either endangered or threatened throughout all or
a significant portion of its range is not warranted at this time.
Because of the remaining uncertainties regarding the effects of the DWH
oil spill, we will add the bluefin tuna to our Species of Concern list
(http://www.nmfs.noaa.gov/pr/species/concern/#list; See 69 FR 19975,
April 15, 2004 for description of program). This will serve to (1)
increase public awareness about the species; (2) further identify data
deficiencies and uncertainties in the species' status and the threats
it faces; (3) and stimulate cooperative research efforts to obtain the
information necessary to evaluate the species' status and threats.
As stated previously, we also intend to revisit this decision no
later than 2013 once the NRDA analyses have been concluded to determine
whether the DWH oil spill altered the condition of the species.
Authority: 16 U.S.C. 1531 et seq.
Dated: May 26, 2011.
Samuel D. Rauch III,
Deputy Assistant Administrator for Regulatory Programs, National Marine
Fisheries Service.
[FR Doc. 2011-13627 Filed 5-27-11; 11:15 am]
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