[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]



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.


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.

Regional Office, (978) 282-8485; or Marta Nammack, NMFS, Office of 
Protected Resources (301) 713-1401.



    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 
    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.


    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., 
    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 
    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.


    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 

[[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.


    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., 
    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 

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 
    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 
    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 

    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-

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 
    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 
    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 
    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 

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 

[[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 
    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 
    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 

[[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]