[Federal Register Volume 81, Number 63 (Friday, April 1, 2016)]
[Notices]
[Pages 18980-19011]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2016-07440]



[[Page 18979]]

Vol. 81

Friday,

No. 63

April 1, 2016

Part III





 Department of Commerce





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 National Oceanic and Atmospheric Administration





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Endangered and Threatened Wildlife and Plants; Notice of 12-Month 
Finding on Petitions to List the Common Thresher Shark and Bigeye 
Thresher Shark as Threatened or Endangered Under the Endangered Species 
Act (ESA); Notice

  Federal Register / Vol. 81 , No. 63 / Friday, April 1, 2016 / 
Notices  

[[Page 18980]]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[Docket No. 141219999-6234-02]
RIN 0648-XD680


Endangered and Threatened Wildlife and Plants; Notice of 12-Month 
Finding on Petitions to List the Common Thresher Shark and Bigeye 
Thresher Shark as Threatened or Endangered Under the Endangered Species 
Act (ESA)

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.

ACTION: Notice of 12-month finding and availability of status review 
report.

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SUMMARY: NMFS has completed comprehensive status reviews under the 
Endangered Species Act (ESA) for two species of thresher shark in 
response to petitions to list those species. These species are the 
common thresher shark (Alopias vulpinus) and the bigeye thresher shark 
(Alopias superciliosus). Based on the best scientific and commercial 
information available, including the status review report (Young et 
al., 2015), and after taking into account efforts being made to protect 
these species, we have determined that the common thresher (A. 
vulpinus) and bigeye thresher (A. superciliosus) do not warrant listing 
at this time. We conclude that neither species is currently in danger 
of extinction throughout all or a significant portion of its range nor 
likely to become so within the foreseeable future.

DATES: This finding was made on April 1, 2016.

ADDRESSES: The status review report for common and bigeye thresher 
sharks is available electronically at: http://www.nmfs.noaa.gov/pr/species/fish/common-thresher-shark.html and http://www.nmfs.noaa.gov/pr/species/fish/bigeye-thresher-shark.html. You may also receive a copy 
by submitting a request to the Office of Protected Resources, NMFS, 
1315 East-West Highway, Silver Spring, MD 20910, Attention: Thresher 
Shark 12-month Finding.

FOR FURTHER INFORMATION CONTACT: Chelsey Young, NMFS, Office of 
Protected Resources, (301) 427-8491.

SUPPLEMENTARY INFORMATION: 

Background

    On August 26, 2014, we received a petition from Friends of Animals 
to list the common thresher shark (Alopias vulpinus) as threatened or 
endangered under the ESA throughout its entire range, or, as an 
alternative, to list 6 distinct population segments (DPSs) of the 
common thresher shark, as described in the petition, as threatened or 
endangered, and designate critical habitat. On April 27, 2015, we 
received a separate petition from Defenders of Wildlife to list the 
bigeye thresher shark as threatened or endangered throughout its range, 
or, as an alternative, to list any identified DPSs, should we find they 
exist, as threatened or endangered species pursuant to the ESA, and to 
designate critical habitat. We found that the petitioned actions may be 
warranted for both species; on March 3, 2015, and August 11, 2015, we 
published positive 90-day findings for the common thresher (80 FR 
11379) and bigeye thresher (80 FR 48061), respectively, announcing that 
the petitions presented substantial scientific or commercial 
information indicating the petitioned actions of listing each species 
may be warranted, and explaining the basis for those findings. We also 
announced the initiation of a status review of both species, as 
required by Section 4(b)(3)(a) of the ESA, and requested information to 
inform the agency's decision on whether the species warranted listing 
as endangered or threatened under the ESA.

Listing Species Under the Endangered Species Act

    We are responsible for determining whether the common and bigeye 
thresher sharks are threatened or endangered under the ESA (16 U.S.C. 
1531 et seq.). To make this determination, we first consider whether a 
group of organisms constitutes a ``species'' under Section 3 of the 
ESA, then whether the status of the species qualifies it for listing as 
either threatened or endangered. Section 3 of the ESA defines species 
to include ``any subspecies of fish or wildlife or plants, and any 
distinct population segment of any species of vertebrate fish or 
wildlife which interbreeds when mature.'' On February 7, 1996, NMFS and 
the U.S. Fish and Wildlife Service (USFWS; together, the Services) 
adopted a policy describing what constitutes a DPS of a taxonomic 
species (61 FR 4722). The joint DPS policy identified two elements that 
must be considered when identifying a DPS: (1) The discreteness of the 
population segment in relation to the remainder of the species (or 
subspecies) to which it belongs; and (2) the significance of the 
population segment to the remainder of the species (or subspecies) to 
which it belongs.
    Section 3 of the ESA defines an endangered species as ``any species 
which is in danger of extinction throughout all or a significant 
portion of its range'' and a threatened species as one ``which is 
likely to become an endangered species within the foreseeable future 
throughout all or a significant portion of its range.'' Thus, in the 
context of the ESA, the Services interpret an ``endangered species'' to 
be one that is presently at risk of extinction. A ``threatened 
species,'' on the other hand, is not currently at risk of extinction, 
but is likely to become so in the foreseeable future. In other words, a 
key statutory difference between a threatened and endangered species is 
the timing of when a species may be in danger of extinction, either now 
(endangered) or in the foreseeable future (threatened). The statute 
also requires us to determine whether any species is endangered or 
threatened as a result of any of the following five factors: The 
present or threatened destruction, modification, or curtailment of its 
habitat or range; overutilization for commercial, recreational, 
scientific, or educational purposes; disease or predation; the 
inadequacy of existing regulatory mechanisms; or other natural or 
manmade factors affecting its continued existence (ESA, section 
4(a)(1)(A)-(E)). Section 4(b)(1)(A) of the ESA requires us to make 
listing determinations 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 efforts being made by any 
State or foreign nation or political subdivision thereof to protect the 
species. In evaluating the efficacy of existing protective efforts, we 
rely on the Services' joint Policy on Evaluation of Conservation 
Efforts When Making Listing Decisions (``PECE''; 68 FR 15100; March 28, 
2003) for any conservation efforts that have not been implemented, or 
have been implemented but not yet demonstrated effectiveness.

Status Review

    We convened a team of agency scientists to conduct the status 
review for the common and bigeye thresher sharks and prepare a report. 
The status review report of common and bigeye thresher sharks (Young et 
al., 2015) compiles the best available information on the status of 
both species as required by the ESA, provides an evaluation of the 
discreteness and significance of populations in terms of the DPS 
policy, and assesses the current and future extinction risk for both 
species, focusing

[[Page 18981]]

primarily on threats related to the five statutory factors set forth 
above. We appointed a biologist in the Office of Protected Resources 
Endangered Species Conservation Division to undertake a scientific 
review of the life history and ecology, distribution, abundance, and 
threats to common and bigeye thresher sharks. Next, we convened a team 
of biologists and shark experts (hereinafter referred to as the 
Extinction Risk Analysis (ERA) team) to conduct extinction risk 
analyses for both species, using the information in the scientific 
review. The ERA team was comprised of a fishery management specialist 
from NMFS' Highly Migratory Species Management Division, four research 
fishery biologists from NMFS' Southeast, Northeast, Southwest, and 
Pacific Island Fisheries Science Centers, and two natural resource 
management specialists with NMFS' Office of Protected Resources. The 
ERA team had group expertise in shark biology and ecology, population 
dynamics, highly migratory species management, and stock assessment 
science. The status review report presents the ERA team's professional 
judgment of the extinction risk facing common and bigeye thresher 
sharks but makes no recommendation as to the listing status of the 
species. The status review report is available electronically at http://www.nmfs.noaa.gov/pr/species/fish/common-thresher-shark.html and 
http://www.nmfs.noaa.gov/pr/species/fish/bigeye-thresher-shark.html.
    The status review report was subjected to independent peer review 
as required by the Office of Management and Budget Final Information 
Quality Bulletin for Peer Review (M-05-03; December 16, 2004). The 
status review report was peer reviewed by three independent specialists 
selected from the academic and scientific community, with expertise in 
shark biology, conservation and management, and knowledge of thresher 
sharks. The peer reviewers were asked to evaluate the adequacy, 
appropriateness, and application of data used in the status review as 
well as the findings made in the ``Assessment of Extinction Risk'' 
section of the report. All peer reviewer comments were addressed prior 
to finalizing the status review report.
    We subsequently reviewed the status review report, its cited 
references, and peer review comments, and believe the status review 
report, upon which this 12-month finding is based, provides the best 
available scientific and commercial information on the common and 
bigeye thresher sharks. Much of the information discussed below on 
thresher shark biology, distribution, abundance, threats, and 
extinction risk is attributable to the status review report. However, 
we have independently applied the statutory provisions of the ESA, 
including evaluation of the factors set forth in Section 4(a)(1)(A)-
(E), our regulations regarding listing determinations, and our DPS 
policy in making the 12-month finding determination.

Life History, Biology, and Status of the Petitioned Species Common 
Thresher Shark (Alopias vulpinus)

Taxonomy and Species Description

    All thresher sharks belong to the family Alopiidae, genus Alopias, 
and are classified as mackerel sharks (Order Lamniformes). Thresher 
sharks are recognized by their elongated upper caudal lobe (tail fin) 
almost equal to its body length, which is unique to the Alopiidae 
family. There are currently three recognized species of thresher shark: 
common thresher (Alopias vulpinus), bigeye thresher (Alopias 
superciliosus), and pelagic threhser (Alopis pelagicus). Eitner (1995) 
used allozymes to infer phylogenetic relationships in the genus 
Alopias, and suggested the existence of an unrecognized fourth thresher 
shark species. Results from a recent genetics study (Carde[ntilde]osa 
et al., 2014) suggest that this fourth thresher shark species may be a 
second species of pelagic thresher shark; however, more information is 
needed to confirm this. The common thresher shark (Alopias vulpinus) is 
the largest of the thresher shark species and is distinguished from 
other thresher sharks by the presence of labial furrows, the origin of 
the second dorsal fin posterior to the end of the pelvic fin free rear 
tip, and the white color of the abdomen extending upward over the 
pectoral fin bases, and again rearward of the pelvic fins. The common 
thresher shark has moderately large eyes, a broad head, short snout, 
narrow tipped pectoral fins, and lateral teeth without distinct 
cusplets. Dorsal coloration may vary from brown, blue slate, slate 
gray, blue gray, and dark lead to nearly black, with a metallic, often 
purplish, luster. The lower surface of the snout (forward of the 
nostrils) and pectoral fin bases are generally not white and may be the 
same color as the dorsal surface (Compagno, 1984; Goldman, 2009).

Current Distribution

    The common thresher shark is found throughout the world in 
temperate and tropical seas, with a noted tolerance for cold waters as 
well; however, highest concentrations tend to occur in coastal, 
temperate waters (Moreno et al., 1989; Goldman, 2009). In the North 
Atlantic, common thresher sharks occur from Newfoundland, Canada, to 
Cuba in the west and from Norway and the British Isles to the African 
coast in the east (Gervelis and Natanson, 2013). Landings along the 
South Atlantic coast of the United States and in the Gulf of Mexico are 
rare. Common thresher sharks also occur along the Atlantic coast of 
South America from Venezuela to southern Argentina. In the eastern 
Atlantic, the common thresher ranges from the central coast of Norway 
south to, and including, the Mediterranean Sea and down the African 
coast to the Ivory Coast. They appear to be most abundant along the 
Iberian coastline, particularly during spring and fall. Specimens have 
also been recorded at Cape Province, South Africa (Goldman, 2009). In 
the Indian Ocean, the common thresher is found along the east coast of 
Somalia, and in waters adjacent to the the Maldive Islands and Chagos 
archipelago. The species is also present off Australia (Tasmania to 
central Western Australia), Sumatra, Pakistan, India, Sri Lanka, Oman, 
Kenya, the northwestern coast of Madagascar and South Africa. A few 
specimens have been taken from southwest of the Chagos archipelago, the 
Gulf of Aden, and northwest Red Sea. However, Romanov (2015) raises 
serious questions regarding the occurrence of common thresher in the 
equatorial and northern tropical Indian Ocean, suggesting the species 
demonstrates strong fidelity to subtropical and temperate coasts of 
South Africa and Australia. In the western Pacific Ocean, the range of 
common thresher includes southern Japan, Korea, China, parts of 
Australia and New Zealand. They are also present around several Pacific 
Islands, including New Caledonia, Society Islands, Fanning Islands, 
Hawaii and American Samoa. In the Northeast Pacific Ocean, the 
geographic range of common thresher sharks extends from Goose Bay, 
British Columbia, Canada to the Baja Peninsula, Mexico and out to about 
200 miles (322 km) from the coast (Goldman, 2009). Additionally, they 
are found off Chile and records exist from Panama (Compagno, 1984; 
Ebert et al., 2014).

Habitat Use and Movement

    The common thresher shark is a highly migratory, pelagic species of 
shark that is both coastal, ranging over continental and insular 
shelves, and epipelagic, ranging far from land, though they are most 
abundant near land approximately 40-50 nautical miles (74-93 km) from 
shore (Strasburg,

[[Page 18982]]

1958; Bedford, 1992). Although the species is migratory, A. vulpinus 
appears to exhibit little to no immigration and emigration between 
geographic areas; namely between the Pacific and Northwest Atlantic 
populations (Gubanov, 1972; Moreno et al., 1989; Bedford, 1992; Trejo, 
2005). In the eastern Pacific, conventional tagging data (N = 110 tag 
returns) from NMFS' Southwest Fisheries Science Center (SWFSC) show 
that common threshers often migrate between the United States and 
Mexico on the West Coast. While these data confirm active transboundary 
migration in this species between the United States and Mexico, there 
is no evidence to support regular migration beyond the West Coast of 
North America. Similarly, in the Atlantic, mark recapture data (number 
tagged = 203 and recaptures = 4) from the NMFS Cooperative Shark 
Tagging Program (CSTP) between 1963 and 2013 provide supporting 
evidence that common thresher sharks do not make transatlantic 
movements (Kohler et al., 1998; NMFS, unpublished data). The range of 
movement for common threshers based on CSTP data was relatively small, 
with an observed maximum straight-line distance travelled of 86 
nautical miles (nmi; 159 km) in the Northwest Atlantic and 271 nmi (502 
km) in the Northeast Atlantic.
    Several studies have shown that common thresher sharks make daily 
vertical migrations, moving to deeper water during the day, with a 
maximum depth reported to 640 m in Australia. In the Marshall Islands, 
common thresher sharks showed a preference for an optimum swimming 
depth, water temperature, salinity and dissolved oxygen range of 160-
240 m, 18-20 [deg]C, 34.5-34.8 ppt and 1.0-1.5 ml/l, respectively, 
during daytime (Cao et al., 2011). These studies indicate that common 
thresher sharks may spend most of the day at deeper depths below the 
thermocline (>200 m) and most of the night in shallower waters between 
0-200 m. Juveniles occupy relatively shallow water over the continental 
shelf (<200 m), while adults are found in deeper water (up to at least 
366 m, with dive depths up to at least 640 m), but rarely range beyond 
200 nmi (321.87 km) from the coast. Both adults and juveniles are 
associated with highly biologically productive waters, found in regions 
of upwelling or intense mixing (PFMC, 2003; Smith et al., 2008).

Diet

    Common thresher sharks feed at mid-trophic levels on a mix of small 
pelagic fish and cephalopods (Cort[eacute]s, 1999; Bowman et al., 2000; 
Estrada et al., 2003; MacNeil et al., 2005). Studies from the U.S. West 
Coast and southern coast of Australia showed common thresher sharks 
exhibit narrower dietary preferences in comparison to other local 
pelagic shark species (Preti et al., 2012; Rogers et al., 2012). Given 
their more specialized diet, they are more likely to exert top-down 
effects on their prey, although this remains to be demonstrated. Based 
on studies at NMFS' SWFSC, the top six prey species, in order, are 
northern anchovy, Pacific sardine, Pacific hake, Pacific mackerel, jack 
mackerel, and market squid (Preti et al., 2001; 2004; 2012).

Reproduction

    Compared to the other Alopias species, the common thresher (A. 
vulpinus) has the fastest growth rate and also attains the largest 
size, and thus matures at an earlier age, between 5 and 12 years 
depending on the geographic location (Smith et al., 2008; Gervelis and 
Natanson, 2013). In terms of size, females attain maturity generally 
around 315-400 cm total length (TL) while males reach maturity at 
similar sizes (generally around 314-420 cm TL) (see Table 1 in Young et 
al., 2015). Female common thresher sharks utilize a mode of 
reproduction of aplacental ovoviviparity and oophagy (i.e., eggs are 
deposited into one of two uterine horns and developing embryos are 
nourished by feeding on other eggs), and gestation is thought to be 
around 9 months (PFMC, 2003; Smith et al., 2008). Litter sizes are 
typically small, and may vary depending on geographic location; they 
range from only 2 pups in the Indian Ocean to between 3 and 7 in the 
Northeast Atlantic, while 3-4 pups are common in the Eastern Pacific 
(with occasional litters of up to 6 pups off California). Pupping is 
thought to occur in the springtime, with mating thought to occur in the 
summer in both the Northeast Atlantic and Eastern Pacific. However, 
pregnant females in the western Indian Ocean have been observed in 
August and November, indicating that birth of young common thresher 
sharks may occur throughout the year in this area (Goldman, 2009).

Size and Growth

    Historical records indicate the common thresher can reach maximum 
lengths of 690-760 cm TL (Bigelow and Schroeder, 1948; Hart, 1973). 
More recent studies report A. vulpinus reaching 573 cm TL and possibly 
up to 600 cm depending on sex and geographic location (Smith et al., 
2008; Goldman, 2009). The lifespan of common threshers has been broadly 
estimated to be between 15 and 50 years (Gervelis and Natanson, 2013); 
however, most recently, longevity of common threshers was estimated to 
be 38 years based on bomb radiocarbon validation (Natanson et al., in 
press). Male common thresher sharks are thought to grow faster than 
females (with a growth coefficient, k, of 0.17/year for males and 0.09/
year for females) but reach a smaller asymptotic size (225.4 cm fork 
length (FL) for males versus 274.5 cm FL for females) (Gervelis and 
Natanson, 2013). Using life history parameters from the eastern North 
Pacific, Cort[eacute]s et al. (2012) estimated productivity of the 
common thresher shark, determined as intrinsic rate of population 
increase (r), to be 0.121 per year (median). However, it should be 
noted that this study relied on an earlier estimated age at maturity 
for A. vulpinus females from the eastern North Pacific (i.e., 5-6 
years) and did not take into account more recent age at maturity 
estimates calculated for A. vulpinus females in the Northwest Atlantic 
(i.e., 12 years), which may slightly decrease the species' overall 
productivity. Overall, the best available data indicate that the common 
thresher shark is a long-lived species (at least 20-40 years) and can 
be characterized as having relatively low productivity (based on the 
Food and Agriculture Organization of the United Nations (FAO) 
productivity indices for exploited fish species, where r < 0.14 is 
considered low productivity), making them generally vulnerable to 
depletion and potentially slow to recover from overexploitation.

Current Status

    Common thresher sharks can be found worldwide, with no present 
indication of a range contraction. Although potentially rare in a large 
portion of its range and generally not targeted, they are caught as 
bycatch in many global fisheries, including bottom and pelagic longline 
tuna and swordfish fisheries, purse seine fisheries, coastal gillnet 
fisheries, and artisanal fisheries. Common thresher sharks are more 
commonly utilized for their meat than fins, as they are a preferred 
species for human consumption; however, they are also valuable as 
incidental catch for the international shark fin trade.
    In 2009, the International Union for Conservation of Nature (IUCN) 
considered the common thresher shark to be Vulnerable globally, based 
on an assessment by Goldman et al. (2009) and its own criteria (A2bd, 
3bd and 4bd), and placed the species on its ``Red List.'' Under 
criteria A2bd, 3bd and 4bd, a species may be classified as Vulnerable 
when its ``observed, estimated, inferred or suspected''

[[Page 18983]]

population size is reduced by 30 percent or more over the last 10 
years, the next 10 years, or any 10-year time period, or over a 3-
generation period, whichever is the longer, where the reduction or its 
causes may not have ceased or may not be understood or may not be 
reversible, based on an index of abundance appropriate to the taxon 
and/or the actual or potential levels of exploitation. The IUCN's 
justification for the categorization is based on the species' declining 
populations. The IUCN notes that the species' regional trends, slow 
life history characteristics (hence low capacity to recover from 
moderate levels of exploitation), and high levels of largely unmanaged 
and unreported mortality in target and bycatch fisheries, give cause to 
suspect that the population has decreased by over 30 percent and meets 
the criteria to be categorized as Vulnerable globally. As a note, the 
IUCN classification for the common thresher shark alone does not 
provide the rationale for a listing recommendation under the ESA, but 
the classification and the sources of information that the 
classification is based upon are evaluated in light of the standards on 
extinction risk and impacts or threats to the species.

Distinct Population Segment Analysis

    As described above, the ESA's definition of ``species'' includes 
``any subspecies of fish or wildlife or plants, and any distinct 
population segment (DPS) of any species of vertebrate fish or wildlife 
which interbreeds when mature.'' As stated in the joint DPS policy, 
Congress expressed its expectation that the Services would exercise 
authority with regard to DPSs sparingly and only when the biological 
evidence indicates such action is warranted. NMFS determined at the 90-
day finding stage that the petition to list the common thresher shark 
as six DPSs (Eastern Central Pacific, Indo-West Pacific, Northwest and 
Western Central Atlantic, Southwest Atlantic, Mediterranean, and 
Northeast Atlantic) did not present substantial scientific or 
commercial information to support the identification of these 
particular DPSs. As such, we conducted the extinction risk analysis on 
the global common thresher shark population.

Assessment of Extinction Risk

    The ESA (Section 3) defines an endangered species as ``any species 
which is in danger of extinction throughout all or a significant 
portion of its range.'' 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.'' Neither we nor the USFWS have developed formal policy guidance 
about how to interpret the definitions of threatened and endangered 
with respect to what it means to be ``in danger of extinction.'' We 
consider the best available information and apply professional judgment 
in evaluating the level of risk faced by a species in deciding whether 
the species is threatened or endangered. We evaluate both demographic 
risks, such as low abundance and productivity, and threats to the 
species, including those related to the factors specified in ESA 
section 4(a)(1)(A)-(E).

Methods

    As we described previously, we convened an ERA team to evaluate 
extinction risk to the species. This section discusses the methods used 
to evaluate threats and the overall extinction risk to the species. For 
purposes of the risk assessment, an ERA team comprised of fishery 
biologists and shark experts was convened to review the best available 
information on the species and evaluate the overall risk of extinction 
facing the common thresher shark now and in the foreseeable future. The 
term ``foreseeable future'' was defined as the timeframe over which 
threats could be reliably predicted to impact the biological status of 
the species. After considering the life history of the common thresher 
shark, availability of data, and type of threats, the ERA team decided 
that the foreseeable future should be defined as approximately 3 
generation times for the common thresher shark, or 30 years. A 
generation time is defined as the time it takes, on average, for a 
sexually mature female common thresher shark to be replaced by 
offspring with the same spawning capacity. This timeframe (3 generation 
times) takes into account the time necessary to provide for the 
conservation and recovery of the species. As a late-maturing species, 
with slow growth rate and relatively low productivity, it would likely 
take more than a generation time for any conservative management action 
to be realized and reflected in population abundance indices. This is 
supported by the fact that we have a well-documented example of how 
this species responds to intense fishing pressure, and the time 
required for the initial implementation of regulatory measures to be 
reflected in population abundance indices. For the northeastern Pacific 
stock of common thresher, the time period from being in an overfished 
state (i.e., lowest point was approximately 30% of virgin reproductive 
output in 1995) to almost fully recovered after the implementation of 
management measures in 1985 was approximately 20-30 years (which 
comports with 3 generation times of the species).
    In addition, the foreseeable future timeframe is also a function of 
the reliability of available data regarding the identified threats and 
extends only as far as the data allow for making reasonable predictions 
about the species' response to those threats. Since the main threats to 
the species were identified as fisheries and the inadequacy of existing 
regulatory measures that manage these fisheries, the ERA team felt that 
they had the background knowledge in fisheries management and expertise 
to confidently predict the impact of these threats on the biological 
status of the species within this timeframe.
    Often the ability to measure or document risk factors is limited, 
and information is not quantitative or is lacking altogether. 
Therefore, in assessing risk, it is important to include both 
qualitative and quantitative information. In assessing extinction risk 
to the species, the ERA team considered the demographic viability 
factors developed by McElhany et al. (2000) and the risk matrix 
approach developed by Wainwright and Kope (1999) to organize and 
summarize extinction risk considerations. The approach of considering 
demographic risk factors to help frame the consideration of extinction 
risk has been used in many of our status reviews (see http://www.nmfs.noaa.gov/pr/species for links to these reviews). In this 
approach, the collective condition of individual populations is 
considered at the species level according to four demographic viability 
factors: abundance, growth rate/productivity, spatial structure/
connectivity, and diversity. These viability factors reflect concepts 
that are well-founded in conservation biology and that individually and 
collectively provide strong indicators of extinction risk.
    Using these concepts, the ERA team evaluated demographic risks by 
assigning a risk score to each of the four demographic risk factors. 
The scoring for these demographic risk criteria correspond to the 
following values: 0--unknown risk, 1--low risk, 2--moderate risk, and 
3--high risk. Detailed definitions of the risk scores can be found in 
the status review report. The ERA team also performed a threats 
assessment for the common thresher shark by evaluating the effect that 
the threat was currently having on the extinction risk of the species. 
The levels included ``low effect,'' ``moderate

[[Page 18984]]

effect'' and ``high effect.'' The scores were then tallied and 
summarized for each threat. It should be emphasized that this exercise 
was simply a tool to help the ERA team members organize the information 
and assist in their thought processes for determining the overall risk 
of extinction for the common thresher shark.
    Guided by the results from the demographic risk analysis and the 
threats assessment, the ERA team members were asked to use their 
informed professional judgment to make an overall extinction risk 
determination for the common thresher shark. For this analysis, the ERA 
team defined three levels of extinction risk: 1--low risk, 2--moderate 
risk, and 3--high risk, which are all temporally connected. Detailed 
definitions of these risk levels are as follows: 1 = Low risk: A 
species may be at a low risk of extinction if it exhibits a trajectory 
indicating that it is not currently experiencing a moderate risk of 
extinction now, nor is it likely to have a high risk of extinction in 
the foreseeable future (see definitions of ``Moderate Risk'' and ``High 
Risk'' below). More specifically, a species may be at low risk of 
extinction due to projected threats and its likely response to those 
threats (i.e., stable or increasing trends in abundance/population 
growth, spatial structure and connectivity, and/or diversity and 
resilience); 2 = Moderate risk: A species is at moderate risk of 
extinction if it exhibits a trajectory indicating that it is likely to 
be at a high risk of extinction in the foreseeable future (see 
description of ``High Risk'' below). More specifically, a species may 
be at moderate risk of extinction due to projected threats and its 
likely response to those threats (i.e., declining trends in abundance/
population growth, spatial structure and connectivity, and/or diversity 
and resilience); 3 = High risk: A species is at high risk of extinction 
when it is currently at or near a level of abundance, spatial structure 
and connectivity, and/or diversity and resilience that place its 
persistence in question. Demographic risk may be strongly influenced by 
stochastic or depensatory processes. Similarly, a species may be at 
high risk of extinction if it faces clear and present threats (e.g., 
confinement to a small geographic area; imminent destruction, 
modification, or curtailment of its habitat; or disease epidemic) that 
are likely to create such imminent demographic risks. The ERA team 
adopted the ``likelihood point'' (FEMAT) method for ranking the overall 
risk of extinction to allow individuals to express uncertainty. For 
this approach, each team member distributed 10 ``likelihood points'' 
among the extinction risk levels. This approach has been used in 
previous NMFS status reviews (e.g., Pacific salmon, Southern Resident 
killer whale, Puget Sound rockfish, Pacific herring, and black abalone) 
to structure the team's thinking and express levels of uncertainty when 
assigning risk categories. Although this process helps to integrate and 
summarize a large amount of diverse information, there is no simple way 
to translate the risk matrix scores directly into a determination of 
overall extinction risk. Other descriptive statistics, such as mean, 
variance, and standard deviation, were not calculated, as the ERA team 
felt these metrics would add artificial precision or accuracy to the 
results. The scores were then tallied and summarized.
    Finally, the ERA team did not make recommendations as to whether 
the species should be listed as threatened or endangered. Rather, the 
ERA team drew scientific conclusions about the overall risk of 
extinction faced by the common thresher shark under present conditions 
and in the foreseeable future based on an evaluation of the species' 
demographic risks and assessment of threats.

Evaluation of Demographic Risks

Abundance

    There is currently a lack of reliable estimates of global 
population size for the common thresher shark, with most of the 
available information indicating that the species is naturally rare in 
a large portion of its range. The ERA team expressed some concern 
regarding the common thresher shark's global abundance, particularly 
given that the species likely experienced localized population declines 
over the past few decades. Given the lack of data, and the fact that 
most of these assessments are not specific to common thresher, the 
extent of the decline and current status of the global population are 
unclear. However, some information, including a recent stock assessment 
and a species-specific analysis of observer data provide some insight 
into current abundance levels of the species.
    In the eastern North Pacific, the NMFS SWFSC conducted the only 
species-specific stock assessment of the common thresher shark to date, 
which incorporates data from the United States and Mexico for the 
period 1969-2014. The U.S. fisheries included the swordfish/shark drift 
gillnet, recreational, nearshore setnet and small-mesh drift gillnet, 
and miscellaneous fisheries. The Mexican fisheries included the 
swordfish/shark drift gillnet, pelagic longline, and artisanal (panga) 
fisheries. This assessment incorporated fisheries-dependent data 
(including estimated removals, size compositions, indices of relative 
abundance, and conditional age-at-length) as well as fisheries-
independent data (e.g., size compositions and a relative abundance 
index for juvenile common thresher sharks). The results of this stock 
assessment indicate that the common thresher shark stock along the West 
Coast of North America (including Mexico and Canada) experienced a 
large decline (>70 percent) in spawning output with the advent of the 
drift gillnet fishery in the late 1970s; however, the decline was 
arrested in the mid-1980s with a series of regulations restricting the 
fishery and the stock has recovered gradually over time. In fact, the 
spawning output in 2014 was estimated to be 94.4 percent of its 
unexploited level. Therefore, the stock is not likely in an overfished 
condition or experiencing overfishing at this time (Teo et al., in 
prep). The ERA team accepted the results of this stock assessment and 
concluded that common thresher shark abundance is likely increasing in 
this portion of its range.
    In the Northwest Atlantic, several studies have been conducted to 
determine trends in abundance of various shark species, including the 
common thresher shark. In the Northwest Atlantic longline fisheries, 
thresher sharks (both common and bigeye threshers) are typically 
recorded at the genus level by observers as well as in logbooks, with 
the bigeye thresher shark typically dominant in the catches. Baum et 
al. (2003) analyzed logbook data for the U.S. pelagic longline fleets 
targeting swordfish and tunas, and reported an 80 percent decline in 
relative abundance for thresher sharks (common and bigeye threshers 
combined) from 1986 to 2000. However, these results were challenged 
(see discussions in Burgess et al. 2005a and Burgess et al. 2005b) on 
the basis of whether correct inferences were made regarding the 
magnitude of shark population declines in the Atlantic. In a more 
recent re-analysis of the same logbook dataset using a similar 
methodology, Cort[eacute]s et al. (2007) reported an overall 63 percent 
decline from 1986-2005, and a 50 percent decline from 1992-2005. In 
contrast, the analysis of the observer dataset from the same fishery 
resulted in an opposite trend to that of the logbook analysis, with a 
28 percent increase in abundance for the same period of 1992-2005 
(Cort[eacute]s et al., 2010). Baum and

[[Page 18985]]

Blanchard (2010) also analyzed observer data from 1992-2005 and 
reported no change in the population trend over the time period, 
concluding that individual year estimates for thresher sharks suggest 
that the population potentially stabilized. It should be noted that 
while the sample size in the latter observer analysis was very small (n 
= 14-84) compared to that in the logbook analysis (n = 112-1292) (Kyne 
et al., 2012), observer data are generally regarded as more reliable 
than logbook data for non-target shark species (Walsh et al., 2002). As 
such, and using a similar approach as Cort[eacute]s et al. (2007), the 
ERA team analyzed the most recent species-specific observer data for 
the common thresher shark from 1992-2013, and found no obvious change 
in the population trend over time, indicating that the population in 
the Northwest Atlantic Ocean has stabilized.
    In other areas of the common thresher shark range, species-specific 
abundance data are absent, rare, or presented as a thresher complex. In 
the Northeast Atlantic and Mediterranean, only one study provided a 
time-series analysis of fishery data specific to common thresher sharks 
(Ferretti et al., 2008). The study, which compiled 9 time series of 
abundance indices from commercial and recreational fishery landings, 
scientific surveys, and sighting records, used generalized linear 
models to extract instantaneous rates of change from each data set, and 
conducted a meta-analysis to compare population trends. Results of this 
study indicate that common thresher abundance in this area decreased by 
96-99 percent over the last two centuries. Most of the other scientific 
information that we and the ERA team reviewed presented data on other 
species of threshers or a thresher complex (see Young et al., 2015). 
For example, one study compared estimates of body mass and indices of 
abundance and biomass derived from data collected in recent years by 
observers on commercial longliners in the tropical Pacific with those 
from a scientific survey conducted in the same general region in the 
early 1950s (Ward and Myers, 2005). This study estimated a decline in 
combined thresher abundance (all three Alopias spp.) of 83 percent, 
with a decline in biomass to approximately 5 percent of virgin levels 
and significant reductions in mean body mass. Mean body mass (kg) also 
declined by nearly 30 percent (from 17 kg to 12 kg). However, in 
addition to the fact that this study does not present data for any 
particular thresher species, the ERA team identified several caveats of 
this study, including variation in locations between surveys and 
differences in data sources (e.g., fishery-independent data vs. 
fishery-dependent data), and seriously questioned the conclusions 
regarding the magnitude of thresher abundance decline. Further, to use 
a thresher complex or other thresher species as a proxy for common 
thresher abundance is erroneous because of the differences in their 
distributions and life history, as well as the proportions they make up 
in commercial catches. When identified to species level, common 
thresher sharks do not appear to be a significant part of the direct or 
incidental shark catch throughout most of their range (e.g., Western 
and Central Pacific Ocean, Indian Ocean, South Atlantic). In fact, some 
evidence suggests that this species may be naturally rare in fisheries 
throughout the tropical Western and Central Pacific and Indian Oceans 
due to its more coastal and temperate distribution. This is evidenced 
by the species' rarity in fisheries data as well as information (albeit 
limited) from genetic studies of shark fins throughout these regions. 
As such, the common thresher's predominantly coastal and temperate 
distribution may buffer the species from exposure to high levels of 
industrial high-seas fishing pressure in a large portion of its range 
that could reduce its abundance. Finally, in most areas showing overall 
declines in Alopiids, the declines are not attributed to common 
threshers, with the exception of the Mediterranean.
    Based on the very limited abundance information available, from 
both fishery-independent and -dependent surveys, and its general rarity 
in fisheries catch in a large portion of its range, the ERA team 
concluded that the common thresher shark has likely declined from 
historical numbers as a result of fishing mortality; however, based on 
the best available information, current common thresher abundance is 
either stable, recovered, or shows no clear trend for most areas. While 
the level of decline in the Mediterranean is concerning, the ERA team 
concluded, and we agree, that the Mediterranean represents a small 
portion of the common thresher shark's global range and likely does not 
affect the global population, particularly given the lack of evidence 
for trans-Atlantic migrations from the Mediterranean to other portions 
of the species' range. Therefore, we conclude that there is no evidence 
to suggest that the species is at a high risk of extinction throughout 
its range, now or in the foreseeable future, due to environmental 
variation, anthropogenic perturbations, or depensatory processes based 
on its current abundance levels.

Growth Rate/Productivity

    Similar to abundance, the ERA team expressed some concern regarding 
the effect of the common thresher shark's growth rate and productivity 
on its risk of extinction. Sharks, in general, have lower reproductive 
and growth rates compared to bony fishes; however, common thresher 
sharks exhibit life-history traits and population parameters that are 
intermediary among other shark species. As previously noted, common 
thresher shark productivity, determined as intrinsic rate of population 
increase (r), has been estimated at 0.121 per year (Cort[eacute]s et 
al., 2012). The species' demographic parameters place it towards the 
moderate to faster growing sharks along a ``fast-slow'' continuum of 
population parameters that have been calculated for 38 species of 
sharks by Cort[eacute]s (2002, Appendix 2). In fact, a number of 
studies have shown common thresher sharks to be among the most 
productive species of sharks. For example, a recent study found that 
common thresher sharks ranked among the highest in productivity when 
compared with other pelagic shark species (ranking 9 out of 26 overall) 
in terms of its egg production, rebound potential, potential for 
population increase, and stochastic growth rate (Chapple and Botsford, 
2013). However, primarily based on the fact that most species of 
elasmobranchs require many years to mature, and have relatively low 
fecundity compared to teleosts (bony fishes), these life history 
characteristics could pose a risk to this species in combination with 
threats that reduce its abundance.

Spatial Structure/Connectivity

    The ERA team did not identify habitat structure or connectivity as 
a potential risk to the common thresher shark. Habitat characteristics 
that are important to the common thresher shark are largely unknown, as 
are nursery areas. The common thresher is a relatively widespread 
species, with multiple stocks in the Pacific, Indian, and Atlantic 
oceans. The population exchange between these stocks is unknown but 
probably low, so loss of a single stock would not constitute a risk to 
the entire species. Additionally, there is currently no evidence of 
female philopatry, the species is highly mobile, and there is little 
known about specific migration routes. It is also unknown if there are 
source-sink dynamics at work that may affect population growth or 
species' decline. Finally, there is no information on critical source

[[Page 18986]]

populations to suggest spatial structure and/or loss of connectivity 
are presently posing demographic risks to the species. Thus, based on 
the best available information, the ERA team concluded, and we agree, 
that there is insufficient information to support the conclusion that 
spatial structure and connectivity pose significant risks to this 
species' continued existence.

Diversity

    The ERA team concluded that the current level of information 
regarding the common thresher's diversity is either unavailable or 
unknown, such that the contribution of this factor to the extinction 
risk of the species cannot be determined at this time. There is no 
evidence that the species is at risk due to a substantial change or 
loss of variation in genetic characteristics or gene flow among 
populations. This species is found in a broad range of habitats and 
appears to be well-adapted and opportunistic. Additionally, there are 
no restrictions to the species' ability to disperse and contribute to 
gene flow throughout its range, nor is there evidence of a substantial 
change or loss of variation in life-history traits, population 
demography, morphology, behavior, or genetic characteristics. Based on 
this information, the ERA team concluded, and we agree, that there is 
insufficient information to support the conclusion that diversity poses 
significant risks to this species' continued existence.

Summary of Factors Affecting the Common Thresher Shark

    As described above, section 4(a)(1) of the ESA and NMFS' 
implementing regulations (50 CFR 424.11(c)) state that we must 
determine whether a species is endangered or threatened because of any 
one or a combination of the following factors: The present or 
threatened destruction, modification, or curtailment of its habitat or 
range; overutilization for commercial, recreational, scientific, or 
educational purposes; disease or predation; the inadequacy of existing 
regulatory mechanisms; or other natural or manmade factors affecting 
its continued existence. The ERA team evaluated whether and the extent 
to which each of the foregoing factors contributed to the overall 
extinction risk of the global common thresher shark population. This 
section briefly summarizes the ERA team's findings and our conclusions 
regarding threats to the common thresher shark. More details can be 
found in the status review report (Young et al., 2015).

The Present or Threatened Destruction, Modification, or Curtailment of 
its Habitat or Range

    The ERA team did not identify habitat destruction as a potential 
threat to the common thresher shark. As described earlier (see Species 
Description--Habitat Use and Movement section), the common thresher 
shark is found worldwide, and resides in coastal temperate and tropical 
seas, with a noted tolerance for colder waters. Common thresher sharks 
are both coastal, ranging over continental and insular shelves, and 
epipelagic, ranging far from land, though they are most abundant near 
land approximately 40-50 nautical miles (nmi; 74-93 km) from shore 
(Strasburg, 1958; Bedford, 1992). However, little else is known 
regarding specific habitat preferences or characteristics.
    In the U.S. exclusive economic zone (EEZ), the Magnuson-Stevens 
Fishery Conservation and Management Act (MSA) (16 U.S.C. 1801 et seq.) 
requires NMFS to identify and describe essential fish habitat (EFH) in 
fishery management plans (FMPs), minimize the adverse effects of 
fishing on EFH, and identify actions to encourage the conservation and 
enhancement of EFH. To that end, NMFS has funded two cooperative survey 
programs intended to help delineate shark nursery habitats in the 
Atlantic and Gulf of Mexico. The Cooperative Atlantic States Shark 
Pupping and Nursery Survey and the Cooperative Gulf of Mexico States 
Shark Pupping and Nursery Survey are designed to assess the 
geographical and seasonal extent of shark nursery habitat, determine 
which shark species use these areas, and gauge the relative importance 
of these coastal habitats for use in EFH determinations. For the common 
thresher, results from the surveys indicate the importance of coastal 
waters off the East Coast of the Atlantic, from Maine to the Florida 
Keys, areas scattered in the Gulf of Mexico from the southern coast of 
Florida to Texas, and areas south and southwest of Puerto Rico (NMFS, 
2009). As a side note, insufficient data are available to differentiate 
EFH by size classes in the Atlantic; therefore, EFH is the same for all 
life stages. Since common thresher shark EFH is defined as the water 
column or attributes of the water column, NMFS determined that there 
are minimal or no cumulative anticipated impacts to the EFH from gear 
used in U.S. Highly Migratory Species (HMS) and non-HMS fisheries, 
basing its finding on an examination of published literature and 
anecdotal evidence (NMFS, 2006).
    On the U.S. West Coast, common thresher pups are found in near-
shore waters of the Southern California Bight. Essential fish habitat 
is described for three age classes in this area: Neonate/early 
juveniles, late juveniles/subadults, and adults. For neonate/early 
juveniles (<102 cm FL), EFH includes epipelagic, neritic and oceanic 
waters off beaches, in shallow bays, in near surface waters from the 
U.S.-Mexico EEZ border north to off Santa Cruz, over bottom depths of 6 
to 400 fathoms (fm; 11-732 m), particularly in water less than 100 fm 
(183 m) deep and to a lesser extent farther offshore between 200-300 fm 
(366-549 m). For late juveniles/subadults (>101 cm FL and <167 cm FL), 
EFH is described as epipelagic, neritic and oceanic waters off beaches 
and open coast bays and offshore, in near-surface waters from the U.S.-
Mexico EEZ border north to off Pigeon Point, California, from the 6 to 
1,400 fm (11-2,560 m) isobaths. For adults (>166 cm FL), EFH is 
described as epipelagic, neritic and oceanic waters off beaches and 
open coast bays, in near surface waters from the U.S.-Mexico EEZ border 
north seasonally to Cape Flattery, WA, from the 40 fm (73 m) isobath 
westward to approximately north of the Mendocino Escarpment and from 
the 40 to 1,900 fm (73-3,474 m) isobaths south of the Mendocino 
Escarpment. In the U.S. Western Pacific, including Hawaii, American 
Samoa, Guam, and the Commonwealth of the Northern Mariana Islands, EFH 
for common thresher sharks is broadly defined as the water column down 
to a depth of 1,000 m (547 fm) from the shoreline to the outer limit of 
the EEZ (WPFMC, 2009).
    Common thresher shark habitat in other parts of its range is 
assumed to be similar to that in the Northwest Atlantic and Gulf of 
Mexico, comprised of open ocean environments occurring over broad 
geographic ranges and characterized primarily by the water column 
attributes. As such, large-scale impacts, such as global climate 
change, that affect ocean temperatures, currents, and potentially food 
chain dynamics, may pose a threat to this species. Studies on the 
impacts of climate change specific to thresher sharks have not been 
conducted; however, there are a couple of studies on other pelagic 
shark species that occur in the range of the common thresher shark. For 
example, Chin et al. (2010) conducted an integrated risk assessment for 
climate change to assess the vulnerability of pelagic sharks, as well 
as a number of other chondrichthyan species, to climate change on the 
Great Barrier Reef (GBR). The assessment examined

[[Page 18987]]

individual species but also lumped species together in ecological 
groups (such as freshwater and estuarine, coastal and inshore, reef, 
shelf, etc.) to determine which groups may be most vulnerable to 
climate change. The assessment took into account the in situ changes 
and effects that are predicted to occur over the next 100 years in the 
GBR and assessed each species' exposure, sensitivity, and adaptive 
capacity to a number of climate change factors including: water and air 
temperature, ocean acidification, freshwater input, ocean circulation, 
sea level rise, severe weather, light, and ultraviolet radiation. Of 
the 133 GBR shark and ray species, the assessment identified 30 as 
being moderately or highly vulnerable to climate change. The pelagic 
shark species included in the assessment, however, were not among these 
species. In fact, the pelagic shark group was ranked as having a low 
overall vulnerability to climate change, with low vulnerability to each 
of the assessed climate change factors. In another study on potential 
effects of climate change to sharks, Hazen et al. (2012) used data 
derived from an electronic tagging project (Tagging of Pacific 
Predators Project) and output from a climate change model to predict 
habitat and diversity shifts in top marine predators in the Pacific out 
to the year 2100. Results of the study showed significant differences 
in habitat change among species groups, which resulted in species-
specific ``winners'' and ``losers.'' The shark guild as a whole had the 
greatest risk of pelagic habitat loss. However, the model predictions 
in Hazen et al. (2012) and the vulnerability assessment in Chin et al. 
(2010) represent only two very broad analyses of how climate change may 
affect pelagic sharks, and do not account for factors such as species 
interactions, food web dynamics, and fine-scale habitat use patterns 
that need to be considered to more comprehensively assess the effects 
of climate change on the pelagic ecosystem. Further, results of these 
studies are not specific to thresher sharks, and finally, the 
complexity of ecosystem processes and interactions complicate the 
interpretation of modeled climate change predictions and the potential 
impacts on populations. Thus, the potential effects of climate change 
on common thresher sharks and their habitat are highly uncertain.
    Overall, the common thresher shark is highly mobile throughout its 
range, and although very little information is known on habitat use or 
pupping and nursery areas, there is no evidence to suggest its access 
to suitable habitat is restricted. The ERA team noted that common 
threshers are not reliant on estuarine habitats, which are thought to 
be one of the most vulnerable habitat types to climate change. 
Additionally, common threshers are likely more confined by temperature 
and prey distributions than a particular habitat type. The highly 
migratory nature of the common thresher shark gives it the ability to 
shift its range or distribution to remain in an environment conducive 
to its physiological and ecological needs. Therefore, while effects 
from climate change have the potential to pose a threat to sharks in 
general, including habitat changes (e.g., changes in currents and ocean 
circulation) and potential impacts to prey species, species-specific 
impacts to common threshers and their habitat are currently unknown, 
but likely minimal. Overall, it is very unlikely that the loss or 
degradation of any particular habitat type would have a substantial 
effect on the common thresher population. Thus, based on the best 
available information, we conclude that current evidence does not 
indicate that there exists a present or threatened destruction, 
modification, or curtailment of the common thresher shark's habitat or 
range.

Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    The common thresher shark is considered desirable for human 
consumption and a highly prized game fish; thus, it is a valuable 
bycatch and target species, which increases its susceptibility to being 
overfished. The ERA team assessed three different factors that may 
contribute to the overutilization of the common thresher shark: Bycatch 
in commercial fisheries (including at-vessel and post-release mortality 
rates), targeting in recreational fisheries, and the global shark trade 
(including the trade of both common thresher fins and meat). Common 
thresher sharks are caught as bycatch in many global fisheries, 
including bottom and pelagic longline fisheries, purse seine fisheries, 
coastal gillnet fisheries, and artisanal fisheries. As a primarily 
coastal and temperate species, the common thresher shark is relatively 
rare in catches of tropical fisheries, particularly in the Western and 
Central Pacific and Indian Oceans. They are also rare in catches of 
fisheries operating in the South Atlantic. Though it is generally not a 
target species in commercial fisheries, it is valued for both its meat 
and fins, and is therefore valued as incidental catch for the 
international shark trade (Clarke et al., 2006a; Dent and Clarke, 
2015).
    As noted previously in the Evaluation of Demographic Risks--
Abundance section, there is very little information on the historical 
abundance, catch, and trends of common thresher sharks, with the 
exception of U.S. data from the Northeast Pacific and Northwest 
Atlantic. The species is only occasionally mentioned in fisheries 
records from the Western and Central Pacific and Indian Oceans, and is 
considered rare in fisheries of the South Atlantic. Although more 
countries and regional fisheries management organizations (RFMOs) are 
working towards better reporting of fish catches down to species level, 
catches of common threshers have gone and continue to go unrecorded in 
many countries. Additionally, many catch records that do include 
thresher sharks do not differentiate between the Alopias species or 
shark species in general, and if they do, they are often plagued by 
species misidentifications. These numbers are also likely under-
reported in catch records, as many records do not account for discards 
(e.g., where the fins are kept but the carcass is discarded) or reflect 
dressed weights instead of live weights. Thus, the lack of catch data 
for common thresher sharks makes it difficult to estimate rates of 
fishing mortality or conduct detailed quantitative analyses of the 
effects of fishing on common thresher populations.
    In the eastern North Pacific, common thresher sharks were 
historically targeted and caught in the California drift gillnet 
swordfish/pelagic shark fishery beginning in the late 1970s. The 
California fishery for common threshers peaked in 1982 with estimated 
landings of approximately 1,800 mt, and then sharply declined in 1986, 
when all subadults were virtually eliminated from the population due to 
overfishing (Camhi et al., 2009; Goldman, 2009). As a result, the 
common thresher population experienced a significant historical 
decline, with approximately 77 percent of the spawning potential 
relative to the unfished stock removed by fishing during that period. 
Catch-per-unit-effort (CPUE) also declined during this time period. By 
1990, the fishery shifted to a swordfish fishery primarily due to 
economic drivers, but also to protect pupping female thresher sharks 
(PFMC, 2003), with a series of regulations restricting the time-areas 
allowed for fishing, gear configurations, and bycatch limitations. 
Commercial landings from the U.S. West Coast swordfish/shark drift 
gillnet fishery declined from 1,800 mt in the early 1980s to 
approximately 10 mt by 18

[[Page 18988]]

vessels in 2014. From 2004-2014, annual U.S. commercial landings 
averaged around 115 mt (PFMC, 2015), which is below the current 
established sustainable and precautionary harvest level of 340 mt and 
well below the current maximum sustainable yield (MSY) of the species 
(i.e., 806 mt).
    Overall, the California drift gill net fishery serves as a well-
documented case of marked population depletion of a small, localized 
stock of common thresher shark over a short time period (less than a 
decade) followed by a gradual recovery after the implementation of 
regulatory measures. Based on the recent stock assessment results of 
Teo et al. (in prep), the common thresher stock along the West Coast of 
North America is not considered overfished and overfishing is not 
occurring. In fact, the eastern North Pacific stock of common thresher 
has recovered to approximately 94 percent of its pre-fished levels.
    In other areas of the Eastern Pacific, the level of utilization of 
common thresher is unclear. Common threshers are taken in artisanal, 
pelagic longline and gillnet fisheries targeting pelagic sharks off 
Mexico's Pacific Coast (Sosa-Nishizaki et al., 2008); however, the 
recent stock assessment for the eastern North Pacific stock of common 
thresher (described above) includes removals from these Mexican 
fisheries, and deemed these removal levels as sustainable (Teo et al., 
in prep). Farther south, the common thresher shark is reportedly caught 
in longline and gillnet fisheries in Peru and has been reported as the 
sixth most important commercial shark species in Peruvian fisheries, 
representing 6 percent of total shark landings (Romero Camarena and 
Bustamante Ruiz, 2007; Gonzalez-Pestana et al., 2014). However, it is 
highly likely that these records were misidentified pelagic thresher 
sharks, as a recent genetic study focused on landings of the small-
scale Peruvian shark fishery discovered a long-term misidentification 
between common and pelagic thresher sharks at landing points (Velez-
Zuazo et al., 2015). Although the common thresher is the only species 
listed in official Peruvian landing reports, all samples in the 
aforementioned study labeled as thresher shark corresponded to pelagic 
thresher shark (n = 12), indicating that landing reports in Peru may be 
pooled for all Alopias species, (Velez-Zuazo et al., 2015) with the 
majority possibly comprised of pelagic threshers. Reports of common 
thresher shark landings are uncommon in Costa Rica and Ecuador. 
According to observer data recorded on Costa Rican longline vessels, a 
total of only 23 common thresher sharks were caught from 1999-2010 
(Dapp et al., 2013). Additionally, while both pelagic and bigeye 
thresher sharks are listed as commonly caught species in Ecuadorian 
waters, the common thresher is not listed, and pelagic threshers are 
the dominant thresher species in thresher shark landings (Jacquet et 
al., 2008; Reardon et al., 2009; Martinez-Ortiz et al., 2015). Thus, 
the common thresher shark is seemingly rare in tropical fisheries of 
the Eastern Pacific, likely due to its more temperate distribution.
    In the Western and Central Pacific Ocean, all three thresher shark 
species interact with longline fisheries, with recent catch estimates 
from 1992-2009 indicating that the genus Alopias comprises 
approximately 3 percent of the total shark catch (Clarke, 2014). 
However, most of the available fisheries data from the Western and 
Central Pacific are for the thresher complex (all three Alopias spp.). 
While records of bigeye and pelagic threshers are recorded in the 
catches of fisheries operating in this region, albeit very under-
reported, very little information is available on catches of common 
thresher shark. Both historical observations and the best available 
current information indicate that common threshers are relatively rare 
in this region, as they are not frequently encountered in tropical 
fisheries due to their distribution in more coastal and temperate 
waters. This is evidenced by the lack of catch and genetic records of 
common thresher sharks in areas of high fishing effort, which is 
seemingly concentrated in more tropical waters. For example, in the 
Republic of the Marshall Islands (RMI), while both pelagic and bigeye 
threshers are two of only five species that comprise 80 percent of the 
total annual shark catch, the common thresher is observed in 
substantially lower numbers; only 87 common threshers were taken in RMI 
longline fisheries from 2005-2009, compared to 1,636 bigeye thresher 
sharks, and 1,353 pelagic thresher sharks (Bromhead et al., 2012). 
Likewise, common thresher occurrence in Hawaiian pelagic longline 
fisheries in the Central Pacific is considered uncommon, while the 
bigeye thresher is considered the dominant thresher species 
encountered. For example, Hawaii observer data from 1995-2006 indicated 
a low catch of common thresher sharks (only 7 individuals identified as 
A. vulpinus and 1,246 individuals for the combined category of A. 
vulpinus/A. pelagicus on 26,507 sets total (4.7 percent of total sets), 
both fishery sectors combined) (Young et al., 2015).
    Further, in several analyses of fisheries data from the Western and 
Central Pacific (based on data holdings of the Secretariat of the 
Pacific Community (SPC)) common thresher sharks were characterized as 
``rare'' or ``not frequently encountered'' with the exception of the 
more temperate waters of Australia and New Zealand. For example, in 
analyses of Japanese longline data, where thresher sharks comprise 
approximately 3.44 percent of the total shark catch, the bigeye 
thresher was the dominant thresher species encountered. In order to 
determine the stock status of key shark species in the Western and 
Central Pacific Ocean (including thresher sharks) Clarke et al. (2011) 
conducted an indicator analysis by examining data holdings from the 
Secretariat of the Pacific Community-Oceanic Fisheries Programme (SPC-
OFP) for sharks taken in longline and purse seine fisheries. In 
summary, the indicator analysis showed that the three thresher species 
have divergent, but not necessarily distinct, distributions and 
interact with longline fisheries throughout the Western and Central 
Pacific Ocean. Threshers comprise a notable portion of the longline 
catch only in one particular region of the Central Pacific (just south 
of Hawaii), and mainly in deep sets. While catch rate analysis produced 
no clear trends for the group as a whole, decreasing size trends were 
identified in tropical regions; however, the authors determined that 
these trends were most likely reflective of trends in bigeye thresher 
rather than common or pelagic threshers. Finally, the most recent 
analysis to date of standardized longline CPUE data shows a decline for 
the thresher shark complex in recent years in the region (Rice et al., 
2015), and when combined with decreasing size trends, likely indicates 
some level of population decline of the thresher complex in this area. 
However, based on catch data and the differing distributions between 
the thresher species, the ERA team concluded, and we agree, that it is 
more likely these trends largely reflect those of bigeye thresher 
rather than the common thresher.
    As mentioned previously, common thresher sharks are more prevalent 
in temperate waters, and are more commonly encountered in Australian 
and New Zealand fisheries. Common thresher sharks are caught in a 
number of fisheries operating off the eastern and western coasts of 
Australia, including the Eastern Tuna and Billfish Fishery (ETBF), 
Southern and Eastern Scale Fish

[[Page 18989]]

and Shark Fishery (SESSF) and the Western Tuna and Billfish Fishery 
(WTBF). A number of risk assessments have been conducted for these 
fisheries, in which the common thresher received various scores based 
on its productivity, susceptibility, and encounterability. However, 
although these risk assessments are informative, without any 
corresponding catch and effort data, it is difficult to discern what 
the status of the common thresher shark is in Australian waters. In New 
Zealand, the common thresher is reported as bycatch in New Zealand's 
surface longline fishery. According to observer data, an estimated 
1,304 thresher sharks were caught as bycatch in the New Zealand 
longline fishery from 2006-2009. In 2009, only 37.5 percent of 
threshers were retained, with the remaining 62.5 percent released 
alive. Additionally, a large reduction in longline effort has occurred 
since 2004. We could not find any additional information regarding 
temporal abundance trends in this fishery, but according to the New 
Zealand Fisheries Department, bycatch numbers are considered stable at 
this time (New Zealand Ministry of Fisheries, 2015).
    In the Northwest Atlantic, common threshers are taken predominantly 
in the U.S. pelagic longline (PLL) fishery. Based on the best available 
data, the common thresher population size has likely declined in this 
region due to historical exploitation of the species (see Abundance 
section; Baum et al. (2003), Cort[eacute]s (2007)). However, as 
previously described, these data are largely based on fisheries 
logbooks and are not species-specific, with the bigeye thresher 
representing the majority of the catch. Since 2006 (the last year of 
the fisheries data from the Baum et al. (2003) and Cort[eacute]s (2007) 
papers), the trend is unclear, with some evidence that the population 
has actually stabilized (Baum and Blanchard, 2010). In order to discern 
abundance trends specific to the common thresher, the ERA team 
conducted a species-specific analysis using standardized abundance 
indices derived from U.S. PLL fishery observer data. Results of this 
analysis show that the common thresher shark population in this region 
has likely stabilized since 1990. Reported landings for common thresher 
in the Northwest Atlantic have also remained stable in recent years at 
approximately 21 mt. This indicates that current levels of catch and 
bycatch and associated mortality may be sustainable in this portion of 
the species' range. There is still uncertainty and the problem could 
get worse if longline fishing effort were to increase; however, the 
stabilization of thresher shark populations in the 1990s coincided with 
the first Federal Fishery Management Plan for Sharks in the Northwest 
Atlantic Ocean and Gulf of Mexico, which includes regulations on trip 
limits and quotas (see Factor D--Inadequacy of Existing Regulatory 
Mechanisms for more details). Therefore, under current management 
measures, the ERA team concluded that overutilization is not currently 
occurring in this portion of the common thresher's range to the point 
that it significantly contributes to the species' global risk of 
extinction, now or in the foreseeable future.
    In the Northeast Atlantic and Mediterranean, fisheries data for 
thresher shark landings are scarce and unreliable because they are 
reported irregularly and variably, and it is likely that the two 
thresher species (A. vulpinus and A. superciliosus) are mixed in the 
records (ICES, 2014). Though both adult and juvenile common threshers 
have been reported as bycatch in all fishing gears used in the 
Mediterranean basin, including longline, purse seine, trawl, driftnet, 
trammel net, gillnet, fish traps, and mid-water fisheries, they are 
caught mainly in longline fisheries for tunas and swordfish. The main 
landing nations of thresher sharks in the Northeast Atlantic and 
Mediterranean are Portugal, Spain and France. As discussed earlier in 
the Demographic Assessment--Abundance section, only one study is 
available to suggest that common thresher sharks have declined between 
an estimated 96 and 99 percent in abundance and biomass in the 
Mediterranean Sea over the past two centuries (Ferretti et al., 2008). 
Data from this region suggest that both annual catches and mean weights 
of common thresher shark have fallen significantly as a result of 
fishing mortality. For example, a significant population reduction has 
been observed in Tunisian waters, with small-scale fisheries now 
targeting neonates. Recent investigations also show common thresher 
sharks are being increasingly targeted in the Alboran Sea by the 
illegal large-scale swordfish driftnet fleet based primarily in 
Morocco. Of concern is the fact that the Alboran Sea has been 
identified as a potential nursery area for common threshers, as 
aggregations of gravid females have been observed in this area (Moreno 
and Moron, 1992; Tudela et al., 2005). The intensive fishing pressure 
and potential targeting of common thresher sharks by the swordfish 
driftnet fleet in the Alboran Sea has the potential to significantly 
impact the local population of common threshers in the area, as well as 
affect recruitment into the local population. However, landings of 
thresher shark reported to International Commission for the 
Conservation of Atlantic Tunas (ICCAT) by the European Union (EU) have 
declined significantly in recent years, which may be the result of 
recent regulations enacted by Spain, a top thresher catching country, 
that prohibit the retention and sale of all thresher species (including 
the common thresher shark). As previously mentioned, although the level 
of utilization and potential population decline of common thresher 
shark in the Mediterranean is concerning, the ERA team concluded, and 
we agree, that the Mediterranean is a small portion of the common 
thresher shark's global range and likely does not affect the global 
population. In fact, despite the reported declines, the common thresher 
is still considered one of the most common bycatch species in some 
fisheries operating in this region.
    In the Southwest Atlantic, there is little information on the catch 
rates or trends of thresher sharks. Some countries still fail to 
collect shark data while others collect it but fail to report 
(Fr[eacute]dou et al., 2015). Thresher sharks are taken as bycatch in 
various fisheries, including Cuban, Brazilian, Uruguayan, Taiwanese, 
Japanese, Venezuelan, and Portuguese longline fisheries. However, based 
on the best available information, catches of common thresher sharks 
are relatively rare in the South Atlantic. For example, from 1994-2000, 
the common thresher shark represented only 1.6 percent of the total 
shark catch in the Venezuelan pelagic longline fishery. Likewise, 
although the common thresher has been reported in catches of Brazilian 
Santos longline fishery, the species is characterized as 
``occasional,'' with almost 100 percent of thresher catch in Brazil 
represented by the bigeye thresher. In Uruguayan longline fisheries, 
common thresher CPUE was low from 2001-2005 (ranging from 0.13 in 2002 
to 0.004 in 2005); however, these low CPUE values were directly related 
to the spatial distribution of effort in areas where the occurrence of 
common thresher is naturally lower (Berrondo et al., 2007). 
Additionally, no real trend could be discerned from this dataset. As 
such, the ERA team concluded, and we agree, that the common thresher is 
likely naturally rare in this portion of its range given its more 
temperate distribution and rarity in catches of longline fisheries 
operations in this region. Thus, we conclude that overutilization as a 
result of fishing mortality is not likely

[[Page 18990]]

occurring in the Southwest Atlantic such that it places the species at 
an increased risk of extinction throughout its global range, now or in 
the foreseeable future.
    In an effort to evaluate the vulnerability of specific shark stocks 
to pelagic longline fisheries in the Atlantic Ocean, Cort[eacute]s et 
al. (2012) conducted an Ecological Risk Assessment using observer 
information collected from a number of fleets operating under ICCAT 
(which is the RFMO responsible for the conservation of tunas and tuna-
like species in the Atlantic Ocean and its adjacent seas). Ecological 
Risk Assessments are popular modeling tools that take into account a 
stock's biological productivity (evaluated based on life history 
characteristics) and susceptibility to a fishery (evaluated based on 
availability of the species within the fishery's area of operation, 
encounterability, post capture mortality and selectivity of the gear) 
in order to determine its overall vulnerability to overexploitation 
(Cort[eacute]s et al., 2012). Ecological Risk Assessment models are 
useful because they can be conducted on a qualitative, semi-
quantitative, or quantitative level, depending on the type of data 
available for input. Results from the Cort[eacute]s et al. (2012) 
Ecological Risk Assessment indicate that common thresher sharks face a 
relatively low risk in ICCAT fisheries. Out of the 20 assessed shark 
stocks, common thresher sharks ranked 9th in terms of their 
susceptibility to pelagic longline fisheries in the Atlantic Ocean. The 
population's estimated productivity value (r = 0.121) ranked 8th; 
however, this was based on older life history information and recent 
data suggest common thresher sharks are slightly less productive. 
Overall vulnerability ranking scores (using three different calculation 
methods, and ranked on a scale of 1 to 20 where 1 = highest risk) 
ranged from 9 to 14, indicating that common thresher sharks have 
moderately low vulnerability and face a relatively low risk to 
overexploitation by ICCAT pelagic longline fisheries (Cort[eacute]s et 
al., 2012).
    There are currently no quantitative stock assessments or basic 
fishery indicators available for common thresher sharks or even 
thresher sharks in general in the Indian Ocean. Thus, the level of 
common thresher shark utilization in this region is highly uncertain. 
Both common and bigeye thresher sharks have been reported as bycatch in 
Indian Ocean longline and gillnet fisheries, with thresher sharks as a 
genus comprising an estimated 16 percent of the total shark catch in 
the Indian Ocean, and having reportedly high hooking mortality (Murua 
et al. 2012; IOTC, 2014). However, results from an Ecological Risk 
Assessment that examined the impact of longline fisheries of the Indian 
Ocean on sharks indicate that common thresher sharks face a low risk; 
in fact, common threshers were ranked as the least vulnerable out of a 
total of 16 pelagic shark species (based on their relatively high 
productivity and lower susceptibility scores) (Murua et al., 2012). We 
could not find any studies on the trends in abundance or catch rates of 
common threshers in the Indian Ocean, making it difficult to determine 
the level of exploitation of these species within the ocean basin. In 
fact, we could only find one study from India that reported CPUE rates 
over time for sharks in general. In the Andaman and Nicobar region, 
where catch of common thresher is reportedly most prevalent, total 
shark CPUE declined sharply (approximately 81 percent) from peak CPUE 
in years 1992-1993 to years 1996-1997 (John and Varghese, 2009). 
However, the lack of species-specific CPUE information for common 
thresher sharks, or even genus-level information for thresher sharks, 
makes it difficult to evaluate the potential changes in abundance for 
the species in this region based on John and Varghese (2009) alone. In 
addition, given that common thresher sharks are more commonly found in 
temperate waters, and the prevalence of pelagic threshers in the catch 
of Indonesian fisheries fishing in nearby waters, the reported A. 
vulpinus catch may be misidentified pelagic thresher sharks. Although 
the Indian Ocean Tuna Commission (IOTC) reports that catches and 
associated mortality of thresher sharks are high in the Indian Ocean, 
the available data do not show extensive utilization of common thresher 
shark by these fisheries relative to other shark species, or even other 
thresher species. In fact, a recent working paper from the IOTC 
suggests that common threshers may not even occur in the equatorial and 
northern tropical Indian Ocean, and previous observations of this 
species are likely misidentifications (Romanov, 2015). Thus, we 
conclude that the common thresher's distribution likely buffers it from 
significant impacts as a result of fishing mortality in this part of 
its range, where fishing pressure and inadequate regulatory measures 
may be more problematic. We noted that this threat may also be tempered 
by the species' relatively low vulnerability to high seas fisheries due 
to its wide range and relatively high productivity for a pelagic shark 
species.
    In addition to overutilization in commercial fisheries, the ERA 
team also assessed whether recreational fisheries could be a threat 
driving overutilization of the common thresher shark. Common thresher 
sharks are highly prized game fish in recreational fisheries due to 
their large size and fighting abilities. Information regarding 
recreational fisheries data for common threshers is severely lacking, 
with the exception of the United States, where common threshers are 
popular in both East and West Coast recreational fisheries. In 
particular, the common thresher shark is the focus of a popular 
southern California recreational fishery that targets individuals using 
multiple fishing gears and techniques. Of concern are the high post-
release mortality rates reported for common threshers after being foul-
hooked in the tail and hauled in backwards. Because the common thresher 
shark is an obligate ram-ventilator, which means it requires forward 
motion to ventilate the gills, the reduced ability to extract oxygen 
from the water during capture, as well as the stress induced from these 
capture methods, may influence recovery following release. In fact, 
results from Heberer (2010) revealed that large tail-hooked common 
thresher sharks with prolonged fight times (>=85 min) experienced 100 
percent mortality. However, the recent stock assessment for the eastern 
North Pacific common thresher population includes removals from this 
recreational fishery, and shows that the current amount of recreational 
fishing pressure and associated post-release mortality is sustainable. 
In the Northwest Atlantic, common thresher sharks have increased in 
popularity in U.S. shark fishing tournaments in recent years. For 
example, an estimated 17,834 common thresher sharks were caught in the 
rod and reel fishery in the U.S. Northwest Atlantic from 2004-2013, 
with approximately 70 percent retained. In order to glean information 
on the relative abundance of common thresher sharks in the Northwest 
Atlantic using recreational fisheries data, the ERA team analyzed data 
collected by the NMFS Northeast Fisheries Science Center (NEFSC) at 
five recreational fishing tournaments from 1978 through 2014. These 
shark tournament data from the Northwest Atlantic (including several 
tournaments in New York and New Jersey), accounting for changes in 
effort, show a fairly stable trend in relative abundance through the 
1990s followed by an increasing trend through the end of the time 
series. The ERA team acknowledged that due to the high

[[Page 18991]]

quality of the meat, the majority of common threshers caught in 
recreational fisheries are kept, but these numbers are likely minor, 
especially compared to commercial catches. With most species retained, 
high post-release mortality rates seen in the southern California 
recreational fisheries are irrelevant in the Northwest Atlantic. 
Further, fishing techniques between southern California and the 
Northwest Atlantic are typically different, resulting in mostly mouth-
hooked and higher survivorship of thresher sharks in the Atlantic, 
compared to mostly tail-hooked thresher sharks and lower survivorship 
in California (Pers. comm. NMFS Fisheries Statistics Division, 2015).
    Finally, the ERA team also assessed whether the shark trade could 
be a threat driving overutilization of the common thresher shark. Based 
on Hong Kong fin trade auction data from 1999-2001 and fin weights and 
genetic information, Clarke et al. (2006b) estimated that up to 4 
million thresher sharks (all three Alopias spp.) (range: 2-4 million), 
with an equivalent biomass of around 60,000 mt, are traded annually. 
Thresher sharks as a genus comprised approximately 2.3 percent of the 
total fins traded annually in the Hong Kong market (Clarke et al., 
2006a). The lack of estimates of the global, or even regional, 
population makes it difficult to put these numbers into perspective. As 
a result, the effect at this time of the removals (for the shark fin 
trade) on the ability of the overall population to survive is unknown. 
While the relative proportion of each thresher shark species comprising 
the shark fin trade is not available in this genus-level assessment by 
Clarke et al. (2006a), genetic testing conducted in some fish markets 
provides some (albeit limited) insight into the species-specific 
prevalence of threshers in the shark fin trade. Genetic sampling was 
conducted on shark fins collected from several fish markets throughout 
Indonesia, and revealed that five species (including pelagic and bigeye 
threshers) represented more than 50 percent of the total fins sampled 
(n = 582). Pelagic and bigeye threshers collectively represented nearly 
15 percent of the total fins sampled; however, the common thresher was 
not detected in these samples (Sembiring et al., 2015). Likewise, in 
Taiwan, which has recently surpassed Hong Kong as the world's largest 
fin-trading center (Dent and Clarke, 2015), common thresher sharks were 
not identified in 548 genetically tested meat samples from several 
markets (whereas pelagic and bigeye threshers were both identified as 
present). In yet another genetic barcoding study of fins from the 
United Arab Emirates, the fourth largest exporter in the world of raw 
dried shark fins to Hong Kong, the Alopiidae family represented 5.9 
percent of the trade from Dubai (Jabado et al., 2015); however, common 
threshers were once again not identified in the samples. In fact, we 
could only find one genetic study of fins, from Chile, in which common 
threshers were identified as present in very small numbers. Although it 
is uncertain whether these studies are representative of the entire 
market within each respective country, results of these genetic tests 
provide some information (albeit limited) that suggests the common 
thresher may not be as utilized in the fin trade as other shark 
species, or even its congeners, A. pelagicus and A. superciliosus. 
Additionally, it should be noted that historically, thresher sharks 
were not identified as ``preferred'' or ``first choice'' species for 
fins, with some traders considering thresher fins to be of low quality 
and value (Rose, 1996; FAO, 2002; Gilman et al., 2007; Clarke, pers. 
comm., 2015). Furthermore, recent studies indicate that due to a waning 
interest in fins as well as increased regulations to curb shark 
finning, the shark fin market is declining. In fact, the trade in shark 
fins through China, Hong Kong Special Administrative Region (SAR), 
which has served as an indicator of the global trade for many years, 
rose by 10 percent in 2011 but fell by 22 percent in 2012. 
Additionally, current indications are that the shark fin trade through 
Hong Kong SAR and China will continue to contract (Dent and Clarke, 
2015). In contrast, a surge in the trade of shark meat has occurred in 
recent years. This could be the result of a number of factors, but 
taking the shark fin and shark meat aggregate trends together indicate 
that shark fin supplies are limited by the existing levels of 
chondrichthyan capture production, but shark meat is underutilized by 
international markets (Dent and Clarke, 2015). This suggests that 
historically underutilized chondrichthyan species will be increasingly 
utilized for their meat. However, because the common thresher shark has 
historically been fully utilized for both its fins and meat when 
captured, it is unlikely that this shift in the shark trade would 
create new or increasing demand for the species. Additionally, thresher 
sharks in general tend to have relatively low survival rates on 
longlines (the main gear type catching them) as they are obligate ram 
ventilators (i.e., they have to swim to survive). As a result, a change 
in market demand would not necessarily change the species' mortality 
rates in longline fisheries. Further, in cases where the species is 
alive upon capture, threshers are considered dangerous to handle 
onboard because of their large caudal fin. In fact, some fishermen will 
even cut and release marketable sharks, including threshers, unless 
they are dead or dying to minimize bodily injury during onboard 
handling (Gilman et al., 2007; Clarke, 2011). Thus, based on the best 
available information, the ERA team concluded, and we agree, that the 
common thresher shark is likely not as prevalent in the shark fin trade 
relative to other shark species or even other thresher species. 
Likewise, the shark trade as a whole, including increasing demand for 
shark meat, is not likely a threat contributing to the overutilization 
of the species such that it faces a high risk of extinction throughout 
its global range, now or in the foreseeable future.
    Overall, based on the best available information, the ERA team 
concluded that overutilization is not likely significantly contributing 
to the common thresher's risk of global extinction, now or in the 
foreseeable future. However, due to the paucity of available data, the 
ERA team acknowledged that there are some uncertainties in assessing 
the contribution of the threat of overutilization to the extinction 
risk of the common thresher shark. As results from the Cort[eacute]s et 
al. (2012) and Murua et al. (2012) Ecological Risk Assessments 
demonstrated, the threat of overutilization of common thresher sharks 
may be tempered by the species' relatively low vulnerability to certain 
fisheries, a likely condition of their wide range, rare presence on 
common fishing grounds where fishing pressure is likely most 
concentrated, and their relatively high productivity. Given the above 
analysis and best available information, we do not find evidence that 
overutilization is a threat that is currently placing the species in 
danger of extinction throughout its global range, now or in the 
foreseeable future. The severity of the threat of overutilization is 
dependent upon other risks and threats to the species, such as its 
abundance (as a demographic risk) as well as its level of protection 
from fishing mortality throughout its range. However, at this time, 
there is no evidence to suggest the species is at or near a level of 
abundance that places its current or future persistence in question due 
to overutilization.

[[Page 18992]]

Disease or Predation

    The ERA team did not identify disease or predation as potential 
threats to the common thresher shark, as they could not find any 
evidence to suggest that either is presently contributing significantly 
to the species' risk of extinction. Common thresher sharks likely carry 
a range of parasites, including copepods and cestodes (Love and Moser, 
1983). Specifically, nine species of copepods, genus Nemesis, 
parasitize thresher sharks. These parasites attach themselves to gill 
filaments and can cause tissue damage, which can then impair 
respiration in the segments of the gills (Benz and Adamson, 1999); 
however, there are no existing data to suggest these parasites are 
affecting common thresher shark abundance levels.
    Predation is also not thought to be a factor influencing common 
thresher numbers. The most significant predator on thresher sharks is 
likely humans; however, a study from New Zealand documented predation 
of A. vulpinus by killer whales (Visser, 2005). In a 12-year period 
that documented 108 encounters with New Zealand killer whales, only 
three individuals of A. vulpinus were taken; thus, predation on A. 
vulpinus by killer whales is likely opportunistic and not a 
contributing factor to abundance levels of common threshers. It is 
likely that juvenile common thresher sharks experience predation by 
adult sharks; as a result, juveniles spend approximately the first 3 
years of life in nursery areas until they attain a large enough size to 
avoid predation. The rate of juvenile predation and the subsequent 
impact on the status of common thresher sharks is unknown; however, 
because thresher sharks are born alive, and are already about 150 cm TL 
at birth, predation upon juvenile threshers is likely to be minimal 
(Calliet and Bedford, 1983).
    Therefore, based on the best available information, the ERA team 
concluded, and we agree, that neither disease nor predation is 
currently placing the species in danger of extinction throughout its 
global range, now or in the foreseeable future.

Inadequacy of Existing Regulatory Mechanisms

    The ERA team evaluated existing regulatory mechanisms to determine 
whether they may be inadequate to address threats to the common 
thresher shark. Existing regulatory mechanisms may include Federal, 
state, and international regulations for commercial and recreational 
fisheries, as well as the shark trade. Below is a brief description and 
evaluation of current and relevant domestic and international 
management measures that may affect the common thresher shark. More 
information on these domestic and international management measures can 
be found in the status review report (Young et al., 2015) and other 
recent status reviews of other shark species (Miller et al., 2013 and 
2014).
    In the U.S. Pacific, HMS fishery management is the responsibility 
of adjacent states and three regional management councils that were 
established by the Magnuson-Stevens Act: The Pacific Fishery Management 
Council (PFMC), the North Pacific Fishery Management Council (NPFMC), 
and the Western Pacific Fishery Management Council (WPFMC). On the U.S. 
West Coast, common thresher sharks are managed by the PFMC, under the 
Pacific HMS FMP, as well as the states of California, Oregon, and 
Washington. As a result of declining abundance, and because common 
threshers are considered vulnerable to overexploitation due to their 
low fecundity, long gestation periods, and relatively high age at 
maturation, the HMS FMP proposed a precautionary annual harvest 
guideline of 340 mt for common thresher sharks to prevent localized 
depletion. This guideline was implemented in 2004. Additionally, 
specific measures implemented for the California drift gillnet fishery 
for the purposes of protecting other species also help to protect 
common thresher sharks. Both participation and fishing effort (measured 
by the number of sets) have declined over the years, and industry 
representatives attribute the decline in vessel participation and 
annual effort to regulations implemented to protect marine mammals, 
endangered sea turtles, and seabirds. For example, in 2001, NMFS 
implemented two Pacific sea turtle conservation areas on the West Coast 
with seasonal drift gillnet restrictions to protect endangered 
leatherback and loggerhead turtles. In the larger of the two closures 
(which spans the EEZ north of Point Conception, California (34[deg]27' 
N. latitude) to mid-Oregon (45[deg] N. latitude) and west to 129[deg] 
W. longitude), drift gillnet fishing is prohibited annually within this 
conservation area from August 15 to November 15 to protect leatherback 
sea turtles. The smaller closure was implemented to protect Pacific 
loggerhead turtles from drift gillnet gear during a forecasted or 
concurrent El Ni[ntilde]o event and is located south of Point 
Conception, California and west of 120[deg] W. longitude from June 1 to 
August 31 (72 FR 31756). Since the leatherback closure was enacted, the 
number of active participants in the drift gillnet fishery declined by 
nearly half, from 78 vessels in 2000 to 40 in 2004, and has remained 
under 50 vessels since then. Although implemented for sea turtle 
protection, these closures help protect common thresher sharks from 
fishing pressures related to gillnet fishing (PFMC, 2015). The drift 
gillnet fishery is also managed by a limited entry permit system, with 
mandatory gear standards. The permit is linked to an individual 
fisherman, not a vessel, and is only transferable under very 
restrictive conditions; thus, the value of the vessel does not become 
artificially inflated. To keep a permit active, current permittees are 
required to purchase a permit from one consecutive year to the next; 
however, they are not required to make landings using drift gillnet 
gear. In addition, a general resident or non-resident commercial 
fishing license and a current vessel registration are required to catch 
and land fish caught in drift gillnet gear. A logbook is also required. 
The HMS FMP requires a Federal permit with a drift gillnet gear 
endorsement for all U.S. vessels that fish for HMS within the West 
Coast EEZ and for U.S. vessels that pursue HMS on the high seas 
(seaward of the EEZ) and land their catch in California, Oregon, or 
Washington. In Washington, drift gillnet fishing gear is prohibited and 
landings of thresher sharks are restricted under Washington 
Administrative Code 220-44-050. As previously mentioned, the recovery 
of the eastern North Pacific stock of common thresher is largely 
attributed to these regulatory mechanisms.
    The WPFMC has jurisdiction over the EEZs of Hawaii, Territories of 
American Samoa, Guam, Commonwealth of the Northern Mariana Islands, and 
the Pacific Remote Island Areas, as well as the domestic fisheries that 
occur on the adjacent high seas. The WPFMC developed the Pelagics 
Fishery Ecosystem Plan (FEP; formerly the Fishery Management Plan for 
the Pelagic Fisheries of the Western Pacific Region) in 1986 and NMFS, 
on behalf of the U.S. Secretary of Commerce, approved the Plan in 1987. 
Under the FEP, thresher sharks are designated as Pelagic Management 
Unit Species and are subject to regulations. These regulations are 
intended to minimize impacts to targeted stocks as well as protected 
species. Fishery data are also analyzed in annual reports and used to 
amend the FEP as necessary. In Hawaii and American Samoa, thresher 
sharks are predominantly caught in longline fisheries that operate 
under extensive

[[Page 18993]]

regulatory measures, including gear, permit, logbook, vessel monitoring 
system, and protected species workshop requirements.
    In the Northwest Atlantic, the U.S. Atlantic HMS Management 
Division within NMFS develops regulations for Atlantic HMS fisheries, 
and primarily coordinates the management of Atlantic HMS fisheries in 
Federal waters (domestic) and the high seas (international), while 
individual states establish regulations for HMS in state waters. The 
NMFS Atlantic HMS Management Division currently manages 42 species of 
sharks (excluding spiny dogfish) under the Consolidated HMS FMP (NMFS, 
2006). The management of these sharks is divided into five species 
groups: Large coastal sharks, small coastal sharks, pelagic sharks, 
smoothhound sharks, and prohibited sharks. Thresher sharks are managed 
under the pelagic sharks group, which includes both common and bigeye 
thresher sharks. One way that the HMS Management Division controls and 
monitors this commercial harvest is by requiring U.S. commercial 
Atlantic HMS fishermen who fish for or sell common thresher sharks to 
have a Federal Atlantic Directed or Incidental shark limited access 
permit. These permits are administered under a limited access program, 
and the HMS Management Division is no longer issuing new shark permits. 
As of October 2015, 224 U.S. fishermen are permitted to target sharks 
managed by the HMS Management Division in the Atlantic Ocean and Gulf 
of Mexico, and an additional 275 fishermen are permitted to land sharks 
incidentally (NMFS, 2015). Under a directed shark permit, there is no 
directed numeric retention limit for pelagic sharks, subject to quota 
limitations. An incidental permit allows fishers to keep up to a total 
of 16 pelagic or small coastal sharks (all species combined) per vessel 
per trip. Authorized gear types include: Pelagic or bottom longline, 
gillnet, rod and reel, handline, or bandit gear. There are no 
restrictions on the types of hooks that may be used to catch common 
thresher sharks, and there is no commercial minimum size limit. The 
annual quota for pelagic sharks (other than blue sharks or porbeagle 
sharks) is currently 488 mt dressed weight. In addition to permitting 
and trip limit requirements, logbook reporting or carrying an observer 
onboard may be required for selected commercial fishermen. The head may 
be removed and the shark may be gutted and bled, but the shark cannot 
be filleted or cut into pieces while onboard the vessel and all fins, 
including the tail, must remain naturally attached to the carcass 
through offloading.
    In addition to Federal regulations, individual state fishery 
management agencies have authority for managing fishing activity in 
state waters, which usually extends from 0-3 nmi (5.6 km) off the coast 
in most cases, and 0-9 nmi (16.7 km) off Texas and the Gulf coast of 
Florida. Federally permitted shark fishermen along the Atlantic coast 
and in the Gulf of Mexico and Caribbean are required to follow Federal 
regulations in all waters, including state waters. To aid in 
enforcement and reduce confusion among fishermen, in 2010, the Atlantic 
States Marine Fisheries Commission, which regulates fisheries in state 
waters from Maine to Florida, implemented a Coastal Shark Fishery 
Management Plan that mostly mirrors the Federal regulations for sharks, 
including common thresher sharks.
    Overall, regulations to control for overutilization of common 
threshers in U.S. Atlantic commercial fisheries, including quotas and 
trip limits, are seemingly adequate, as evidenced by stable CPUE trends 
for the species since the 1990s, which corresponds with the 
implementation of management measures for pelagic sharks under the U.S. 
HMS FMP. From 2009 through 2014, commercial landings of common thresher 
sharks have ranged from approximately 15 mt dw to 53 mt dw, and the 
population has seemingly stabilized under existing regulatory 
mechanisms in this region.
    In other parts of the common thresher shark's range, the ERA team 
noted that effective international regulations specific to common 
thresher sharks are lacking, particularly in the Mediterranean. Despite 
several laws and regulatory mechanisms within the region (e.g., EU Ban 
on driftnet fishing in EU waters, ICCAT ban on driftnets for large 
pelagics in the Mediterranean (Rec. 2003-04), and General Fisheries 
Commission of the Mediterranean (GFCM) ban on use of driftnets in the 
Mediterranean), recent investigations show common thresher sharks are 
being increasingly targeted in the Alboran Sea by an illegal large-
scale swordfish driftnet fleet based primarily in Morocco. For example, 
Tudela et al. (2005) monitored 369 fishing operations made by the 
driftnet fleet between December 2002 and September 2003 and estimated a 
total of 4,791 common threshers caught over the 8-month sampling 
period. When extrapolated to 12-months, catches of common thresher 
sharks are estimated at about 7000-8000 individuals in the Alboran Sea 
alone. This suggests that regulatory mechanisms are not adequate in 
this region to control for overutilization as a result of intensive 
fishing pressure. However, some recent regulations may help to curb 
fishing pressure in the region. For example, in 2013, the European 
Parliament passed a regulation prohibiting the removal of shark fins by 
all vessels in EU waters and by all EU-registered vessels operating 
anywhere in the world. Many individual European countries have also 
implemented measures to stop the practice of finning and conserve shark 
populations. For example, in 2009, Spain enacted national legislation 
(Orden ARM/2689/2009) that includes specific measures prohibiting 
Spanish fishing vessels from catching, transshipping, landing and 
marketing of sharks of the Family Alopiidae (all three Alopias spp.) in 
all fisheries. This includes territorial waters of Spain and in other 
EU countries with which there is a fisheries agreement, and in areas 
that can be accessed by private agreement or contract lease of fishing 
vessels. This regulation went into effect in 2010. Given that Spain 
accounts for approximately 7.3 percent of the global shark catch (Lack 
and Sant, 2011) and was the largest exporter of fins in 2008, this 
prohibition has likely decreased total fishing mortality on the 
Atlantic population of thresher sharks. This is potentially evidenced 
by the fact that total EU catches of common threshers dropped 
precipitously by approximately 65 percent from 2009 to 2010, and have 
continued to decline since. Thus, this prohibition may be responsible 
for the significant decline in thresher landings by the EU reported to 
ICCAT since 2010, and may significantly reduce fishing pressure on 
common thresher sharks. In addition, the ERA team agreed that 
overutilization of the species in the Mediterranean, which is a small 
portion of the species' global range, does not necessarily constitute a 
high risk of extinction for the global population, now or in the 
foreseeable future.
    In Indian Ocean waters, the main regulatory body is the IOTC, which 
has management measures in place specifically for thresher sharks that 
prohibit the landing of all Alopias species. Specifically, in 2010, the 
IOTC passed recommendation 10-05 to prohibit the retention, 
transshipment, landing, storing, or offering for sale any part of 
carcass of thresher sharks of the family Alopiidae. The IOTC also 
requires contracting parties (CPCs) to annually report shark catch data 
and provide statistics by species for a select number of sharks, 
including thresher

[[Page 18994]]

sharks (Resolutions 05/05, 11/04, 08/04, 10/03, 10/02). The IOTC also 
developed additional shark conservation and management measures that 
aim to further reduce shark waste and encourage the live release of 
sharks, especially juveniles or pregnant females, caught incidentally 
(and not used for food or other purposes) in fisheries for tunas and 
tuna-like species. However, it is unclear how effective these measures 
have been. For example, in a recent status report, the IOTC's Working 
Party on Ecosystems and Bycatch noted that the International Plan of 
Action for sharks was adopted in 2000, which requires each CPC to 
develop a National Plan of Action (NPOA) for sharks; however, despite 
the time that has elapsed since then, very few CPCs have developed 
NPOAs for sharks, or even carried out assessments to determine whether 
the development of a plan is prudent. Currently, only 12 of the 35 CPCs 
have developed NPOAs for sharks (IOTC, 2014). Additionally, although 
the IOTC is the only RFMO that has specific regulations for all 
thresher species, the IOTC itself acknowledges that species retention 
bans may not be adequate for species that have high bycatch-related 
mortality rates. Overall, however, common threshers in particular do 
not appear to be caught in large numbers by fisheries in the Indian 
Ocean, likely a result of the species' more coastal, temperate 
distribution in areas where high seas longline fisheries operations are 
not as concentrated. In fact, it is quite possible that common thresher 
sharks do not occur in equatorial or tropical waters of the Indian 
Ocean at all (Romanov, 2015). Thus, while regulatory mechanisms to 
control overutilization may be problematic for more prevalent bycatch 
species in this region, inadequate regulations in the Indian Ocean are 
potentially less problematic for the common thresher shark.
    On the U.S. West Coast, recreational fisheries primarily occur in 
non-federal waters (0-3 nmi off the coast) and are managed by the 
states of Washington, Oregon, and California, with inter-state 
coordination facilitated through the Pacific States Marine Fisheries 
Commission. Common thresher sharks may be retained recreationally, 
except in Washington State, where any fishing for Alopias spp. is 
prohibited. California recreational regulations impose a two-fish bag 
limit on thresher sharks. This is cumulative for multi-day trips and 
most anglers seldom fill bag limits. Upon a thorough review of recent 
California Recreational Fishery Survey data, estimates of recreational 
thresher shark catches were not causing cumulative landings to exceed 
the precautionary harvest guideline of 340 t. Further, an analysis of 
bag limits showed that few anglers actually caught and filled their 
legal limits. Finally, and as previously described, a recent stock 
assessment (Teo et al., in prep) confirmed that removal levels of 
common thresher as a result of recreational fisheries are presently 
sustainable and not contributing to the overutilization of the species. 
Thus, it appears that recreational fisheries management of the U.S. 
West Coast population of thresher shark is precautionary, and ensures 
that cumulative catches (recreational + commercial) do not exceed the 
harvest guideline (i.e., 340 mt) nor the maximum sustainable yield 
(MSY) (i.e., 806 mt) for the species.
    In the U.S. Atlantic, an HMS permit (either Angling or Charter/
Headboat) is required for recreational fishing for sharks in Federal 
waters. Common thresher sharks may be retained recreationally using 
authorized fishing gear, including rod and reel and handline. There are 
no restrictions on the types of hooks that may be used to catch 
Atlantic sharks on these gear types. Common thresher sharks that are 
kept must have a minimum size of 54 inches (4.5 feet; 137 cm) FL. 
Sharks that are under the minimum size must be released, and only one 
shark, which could be a common thresher shark, may be kept per vessel 
per trip (note, there are exceptions to the retention limit and size 
limit for Atlantic sharpnose, bonnethead, and smoothhound sharks). 
Since 2008, recreational fishermen have been required to land all 
sharks with their head, fins, and tail naturally attached. Thus, there 
are some management measures in place to regulate recreational catches 
of common thresher sharks, including bag and size limits. As described 
previously, an estimated 17,834 common thresher sharks were caught in 
the rod and reef fishery in the U.S. Northwest Atlantic from 2004-2013, 
with approximately 70 percent retained. Additionally, size limits for 
common thresher sharks imposed by the various states under the ASMFC 
may not be helpful for reducing recreational fishing pressure because 
the size limit (137 cm FL) is significantly lower than the reported 
size of maturity in the Northwest Atlantic, and thus, allows for 
sexually immature juveniles to be caught and landed. However, 
recreational fisheries, and in particular tournaments, may have their 
own size limits that are larger than 137 cm FL because they typically 
tend to target the largest sharks. Despite the increases in popularity 
and targeting of common thresher sharks in recreational fisheries in 
the Northeast United States, standardized tournament data that account 
for changes in effort show increasing relative abundance of common 
thresher sharks in recent years. This information, combined with a 
stable CPUE trend from commercial fisheries, indicates that the 
population is stable and removals via recreational fisheries are likely 
sustainable.
    In addition to commercial and recreational fishing regulations, the 
United States has implemented a couple of significant laws for the 
conservation and management of sharks: the Shark Finning Prohibition 
Act and the Shark Conservation Act. The Shark Finning Prohibition Act 
was enacted in December 2000 and implemented by final rule on February 
11, 2002 (67 FR 6194), and prohibited any person under U.S. 
jurisdiction from: (i) Engaging in the finning of sharks; (ii) 
possessing shark fins aboard a fishing vessel without the corresponding 
carcass; and (iii) landing shark fins without the corresponding 
carcass. It also implemented a five percent fin to carcass ratio, 
creating a rebuttable presumption that fins landed from a fishing 
vessel or found on board a fishing vessel were taken, held, or landed 
in violation of the Act if the total weight of fins landed or found on 
board the vessel exceeded five percent of the total weight of carcasses 
landed or found on board the vessel. The Shark Conservation Act was 
signed into law on January 4, 2011, and, with a limited exception for 
smooth dogfish (Mustelus canis), prohibits any person from removing 
shark fins at sea, or possessing, transferring, or landing shark fins 
unless they are naturally attached to the corresponding carcass.
    After the passage of the Shark Finning Prohibition Act, U.S. 
exports of dried shark fins significantly dropped, which was expected. 
In 2011, with the passage of the U.S. Shark Conservation Act, exports 
of dried shark fins dropped again, by 58 percent, to 15 mt, the second 
lowest export amount since 2001. This is in contrast to the price per 
kg of shark fin, which was at its highest price of ~$100/kg, and 
suggests that existing regulations have likely been effective at 
discouraging fishing for sharks solely for the purpose of the fin 
trade. Thus, although the international shark fin trade is likely a 
driving force behind the overutilization of many global shark species, 
the U.S. participation in this trade appears to be diminishing. In 
2012, the value of fins also decreased, suggesting that the

[[Page 18995]]

worldwide demand for fins may be on a decline. For example, a decrease 
in U.S. fin prices coincided with the implementation of fin bans in 
various U.S. states in 2012 and 2013, and U.S. shark fin exports have 
continued on a declining trend. However, it should be noted that the 
continued decline is also likely a result of the waning global demand 
for shark fins altogether. Similarly, many U.S. states, especially on 
the West Coast, and U.S. Flag Pacific Island Territories have also 
passed fin bans and trade regulations, subsequently decreasing the 
United States' contribution to the fin trade. For example, after the 
State of Hawaii prohibited finning in its waters and required shark 
fins to be landed with their corresponding carcasses in the state in 
2000, the shark fin exports from the United States into Hong Kong 
declined significantly in 2001 (54 percent decrease, from 374 to 171 t) 
as Hawaii could therefore no longer be used as a fin trading center for 
the international fisheries operating and finning in the Central 
Pacific (Clarke et al., 2007). As described previously, landings of 
thresher sharks declined since 2000 in both American Samoa and Hawaii, 
presumably due to the implementation of shark finning regulations. 
Thus, these regulations are likely conferring a conservation benefit 
for thresher sharks.
    Internationally, the RFMOs that cover the Atlantic, Indian and 
Pacific Oceans, including ICCAT, IOTC, the Western and Central Pacific 
Fisheries Commission (WCPFC), and the Inter-American Tropical Tuna 
Commission (IATTC), require the full utilization of any retained 
catches of sharks, with a regulation that onboard fins cannot weigh 
more than five percent of the weight of the sharks (i.e., the five 
percent fin to carcass ratio). These regulations are aimed at curbing 
the practice of shark finning, but do not prohibit the fishing of 
sharks. In addition, these regulations may not be as effective in 
stopping finning of sharks compared to those that require fins to be 
naturally attached, as a recent study found many shark species, 
including the common thresher shark, to have an average wet-fin-to-
round-mass ratio of less than five percent (Biery and Pauly, 2012). In 
other words, fishing vessels operating in these RFMO convention areas 
may be able to land more shark fins than bodies and still pass 
inspection. However, these RFMOs do encourage the release of live 
sharks, especially juveniles and pregnant females that are caught 
incidentally and are not used for food and/or subsistence in fisheries, 
and request the submission of data related to catches of sharks, down 
to the species level where possible.
    While the ERA team initially expressed some concern regarding 
finning of common thresher sharks for the international shark fin 
trade, they noted that the situation appears to be improving due to 
current regulations (e.g., increasing number of finning bans) and 
trends (e.g., waning demand for shark fins), and may not be as severe a 
threat to common thresher sharks compared to other species, as some 
evidence suggests that thresher shark fins are not preferred or ``first 
choice'' among some traders (Rose, 1996; FAO, 2002; Gilman et al., 
2007; Clarke pers. comm. 2015). Additionally, unlike bigeye and pelagic 
thresher shark fins, common thresher shark fins have been rarely 
identified as present in several genetic tests of fins throughout 
various portions of the species' range. Also, as discussed above (with 
further details in Young et al., 2015), finning bans have been 
implemented by a number of countries, as well as by nine RFMOs. These 
finning bans range from requiring fins remain attached to the body to 
allowing fishermen to remove shark fins provided that the weight of the 
fins does not exceed five percent of the total weight of shark 
carcasses landed or found onboard. These regulations are aimed at 
stopping the practice of killing and disposing of shark carcasses at 
sea and only retaining the fins. Although they do not prohibit shark 
fishing, they work to decrease the number of sharks killed solely for 
the international shark fin trade, with some more effective than 
others.
    In addition to these finning bans, there has been a recent push to 
decrease the demand of shark fins, especially for shark fin soup. For 
example, in a recent report from WildAid, Whitcraft et al. (2014) 
reported the following regarding the declining demand for shark fins: 
An 82 percent decline in sales reported by shark fin vendors in 
Guangzhou, China and a decrease in prices (47 percent retail and 57 
percent wholesale) over the past 2 years; 85 percent of Chinese 
consumers surveyed online said they gave up shark fin soup within the 
past 3 years, and two-thirds of these respondents cited awareness 
campaigns as a reason for ending their shark fin consumption; 43 
percent of consumers responded that much of the shark fin in the market 
is fake; 24 airlines, 3 shipping lines, and 5 hotel groups have banned 
shark fin from their operations; there has been an 80 percent decline 
from 2007 levels in prices paid to fishermen in Tanjung Luar and Lombok 
in Indonesia and a decline of 19 percent since 2002-2003 in Central 
Maluku, Southeastern Maluku and East Nusa Tenggara; and of 20 Beijing 
restaurant representatives interviewed, 19 reported a significant 
decline in shark fin consumption. Thus, given that thresher fins are 
not among the most prized in the international shark fin trade (and, in 
fact, are considered of low value to some traders), combined with a 
lack of evidence of common thresher fins in several prominent markets, 
the extent of utilization on common thresher sharks for this trade was 
not viewed as significant enough to decrease the species' abundance to 
the point where it may be at risk of extinction due to environmental 
variation, anthropogenic perturbations, or depensatory processes. 
Additionally, as the supply of shark fins continues to decline (as 
demonstrated by the increase in finning bans and other regulations) and 
demand for shark fins also continues to decline (as demonstrated by 
decreases in prices of shark fin food products), so should the threat 
of finning and illegal harvest. Finally, and as previously discussed 
(refer back to the Overutilization for commercial, recreational, 
scientific, or educational purposes section), although there has been a 
recent shift in demand from shark fins to shark meat, we have no 
evidence to suggest that the species is experiencing increased 
mortality in fisheries as a result of this shift in the international 
market.
    Based on the above review of regulatory measures (in addition to 
the regulations described in Young et al., 2015), the ERA team 
concluded that these existing regulations are not inadequate such that 
they contribute significantly to the species' risk of extinction 
throughout its global range. In fact, the team noted that some areas of 
the species' range do have adequate measures in place to prevent 
overutilization, such as in the Northeast Pacific and Northwest 
Atlantic, where U.S. fishery management measures are helping to monitor 
the catch of common thresher and prevent any further population 
declines. Thus, these U.S. conservation and management measures (as 
previously summarized with additional details in Young et al., 2015) 
are adequate and do not contribute to the extinction risk of the common 
thresher shark by increasing demographic risks (e.g., further abundance 
declines) or the threat of overutilization (e.g., unsustainable catch 
rates) currently and in the foreseeable future. Although regulations 
specific to common thresher sharks are lacking in other parts of its 
range, fishery

[[Page 18996]]

interactions are rare (with the exception of the Mediterranean) and 
thus the effects of the current regulatory measures do not appear to be 
significantly increasing the species' risk of extinction. This species 
appears to be naturally rare in many fisheries throughout its global 
range, and overutilization of the species is not considered a 
significant threat (see Overutilization for Commercial, Recreational, 
Scientific or Educational Purpose section discussed earlier in this 
notice). Therefore, based on the best available information, we find 
that the threat of inadequate regulatory mechanisms is not likely 
contributing to the species' risk of extinction throughout its global 
range; however, we recognize that improvements are needed in the 
monitoring and reporting of fishery interactions of this species.

Other Natural or Manmade Factors Affecting Its Continued Existence

    As previously described, the ERA team assessed the effects of 
climate change as a potential threat to common thresher sharks; 
however, since most of the studied impacts from climate change are 
habitat-focused, the threat of climate change is addressed in the 
Present or Threatened Destruction, Modification, or Curtailment of its 
Habitat or Range section of this finding. Other threats that fall under 
Factor E (ESA section 4(a)(1)(E)), including pollution and potential 
threats to important prey species, are addressed in the status review 
report (Young et al., 2015), but were not identified as threats that 
rose to the level of increasing the species' risk of extinction.

Overall Risk Summary

    Guided by the results from the demographic risk analysis and 
threats assessment, the ERA team members used their informed 
professional judgment to make an overall extinction risk determination 
for the common thresher shark now and in the foreseeable future. The 
ERA team concluded that the common thresher shark currently has a low 
risk of extinction. However, due to the lack of abundance trends and 
catch data for a large portion of the species' range (e.g., Western and 
Central Pacific and Indian Oceans), as well as potentially significant 
declines observed in a small portion of the range (e.g., 
Mediterranean), the ERA team expressed some uncertainty by placing some 
likelihood points in the ``moderate risk'' and ``high risk'' categories 
as well. Likelihood points attributed to the overall level of 
extinction risk categories were as follows: Low Risk (52.5/70), 
Moderate Risk (14.5/70), High Risk (3/70). The ERA team reiterated that 
in most areas (with the exception of the Mediterranean), common 
thresher abundance trends are stable, increasing, or not discernable. 
There is also no evidence to suggest depensatory processes are 
currently at work. The species is found globally, throughout its 
historical range, appears to be well-adapted, and is not limited by 
habitat. The team noted that the only available stock assessment of 
common thresher is from the eastern North Pacific. The stock assessment 
(Teo et al., in prep) shows that although common threshers experienced 
a significant historical decline in the 1980s, the species has 
recovered to more than 90 percent of virgin, pre-fished levels. As 
discussed previously, there were flaws in the other studies cited 
within the status review report, including the fact that most of these 
studies are not species-specific, as well as questionable species 
identification within the datasets (as only recently has more attention 
been paid to accurately identifying thresher sharks down to species). 
Some of these studies have also been criticized for a number of other 
issues, including relying on fisheries logbook data, variation in 
locations between surveys and differences in data sources (e.g., 
fishery-independent data vs. fishery-dependent data), and not 
accounting for other various factors that may have affected the 
outcomes. After considering the flaws within the datasets, as well as 
conducting separate analyses of available and arguably more reliable 
observer data, the ERA team found the results do not demonstrate that 
the common thresher shark is at risk of extinction due to its current 
abundance. Throughout the species' range, observations of its abundance 
are variable, with reports of increasing, decreasing, and stable or no 
trends. The species is also rare in fisheries data in a large portion 
of its range (Western and Central Pacific, Indian, and South Atlantic 
Oceans), either due to lack of reporting or because the species is 
simply not present in common fishing grounds (or not susceptible to 
fishing gear, see Ecological Risk Assessment results). As the main 
threat that the ERA team identified was overutilization due to 
fisheries (with references to historical overutilization), the absence 
of the species in fisheries data in a large portion of its range 
suggests that this threat is either being minimized by existing 
regulations or is not significantly contributing to the extinction risk 
of the species at this time (as the abundance data do not indicate that 
the species has been fished to near extinction).
    The available information indicates that most of the observed 
declines occurred in the 1980s, before any significant management 
regulations. Since then, current regulatory measures in some parts of 
the common thresher shark's range are minimizing the threat of 
overutilization. For example, the recovery of the common thresher 
population on the U.S. West Coast is largely attributed to the 
conservative management regulations implemented for the California 
swordfish/shark gillnet fishery. Additionally, the comprehensive 
science-based management and enforceable and effective regulatory 
structure within the U.S. Northwest Atlantic will help monitor and 
prevent further declines of common thresher sharks while in these 
waters, and the implementation of Spain's regulation on the prohibition 
of landing or selling all Alopias spp. will provide increased 
protection for common thresher sharks throughout the entire Atlantic 
Ocean into the foreseeable future. In the rest of the species' range, 
rare fisheries interactions seem to imply that the species' more 
coastal and temperate distribution may buffer the species from exposure 
to intensive fishing pressure by industrial high seas fisheries, which 
concentrate the majority of fishing effort in more tropical waters. In 
addition, existing management measures (such as RFMO recommendations, 
national shark fishing measures, and shark fin bans) may be effective 
at minimizing overutilization of the species, with trends that are 
moving toward more restrictive trade and decreased demand in shark fin 
products, which indicate a decreased likelihood of extinction of the 
global population in the foreseeable future. Thus, given the best 
available information, the ERA concluded that over the next 30 years, 
it is unlikely that the common thresher shark will have a high risk of 
extinction throughout its global range, due to trends in its abundance, 
productivity, spatial structure, or diversity or influenced by 
stochastic or depensatory processes.

Significant Portion of Its Range

    If we find that the common thresher shark is not in danger of 
extinction now or in the foreseeable future throughout its range, under 
the Significant Portion of its Range (SPR) Policy, we must go on to 
evaluate whether the species is in danger of extinction, or likely to 
become so in the foreseeable future, in a ``significant portion of its 
range'' (79 FR 37578; July 1, 2014).

[[Page 18997]]

    The SPR Policy explains that it is necessary to fully evaluate a 
particular portion for potential listing under the ``significant 
portion of its range'' authority only if substantial information 
indicates that the members of the species in a particular area are 
likely both to meet the test for biological significance and to be 
currently endangered or threatened in that area. Making this 
preliminary determination triggers a need for further review, but does 
not prejudge whether the portion actually meets these standards such 
that the species should be listed. To identify only those portions that 
warrant further consideration, we will determine whether there is 
substantial information indicating that (1) the portions may be 
significant and (2) the species may be in danger of extinction in those 
portions or likely to become so within the foreseeable future. We 
emphasize that answering these questions in the affirmative is not a 
determination that the species is endangered or threatened throughout a 
significant portion of its range--rather, it is a step in determining 
whether a more detailed analysis of the issue is required (79 FR 37578, 
at 37586; July 1, 2014).
    Thus, the preliminary determination that a portion may be both 
significant and endangered or threatened merely requires NMFS to engage 
in a more detailed analysis to determine whether the standards are 
actually met (79 FR 37578, at 37587). Unless both standards are met, 
listing is not warranted. The SPR policy further explains that, 
depending on the particular facts of each situation, NMFS may find it 
is more efficient to address the significance issue first, but in other 
cases it will make more sense to examine the status of the species in 
the potentially significant portions first. Whichever question is asked 
first, an affirmative answer is required to proceed to the second 
question. Id. ``[I]f we determine that a portion of the range is not 
`significant,' we will not need to determine whether the species is 
endangered or threatened there; if we determine that the species is not 
endangered or threatened in a portion of its range, we will not need to 
determine if that portion is `significant' '' Id. Thus, if the answer 
to the first question is negative--whether that regards the 
significance question or the status question--then the analysis 
concludes and listing is not warranted.
    As defined in the SPR Policy, a portion of a species' range is 
``significant'' ``if the species is not currently endangered or 
threatened throughout its range, but the portion's contribution to the 
viability of the species is so important that, without the members in 
that portion, the species would be in danger of extinction, or likely 
to become so in the foreseeable future, throughout all of its range'' 
(79 FR 37578, at 37609). For purposes of the SPR Policy, ``[t]he range 
of a species is considered to be the general geographical area within 
which that species can be found at the time FWS or NMFS makes any 
particular status determination. This range includes those areas used 
throughout all or part of the species' life cycle, even if they are not 
used regularly (e.g., seasonal habitats). Lost historical range is 
relevant to the analysis of the status of the species, but it cannot 
constitute a significant portion of a species' range'' Id.
    Applying the SPR policy to the common thresher shark, we first 
evaluated whether there is substantial information indicating that the 
species may be threatened or endangered in any portion of its range. 
After a review of the best available information, the ERA team 
concluded, and we agree, that the Mediterranean region likely has more 
concentrated threats than other regions of the common thresher's range, 
placing the species at an increased risk of extinction within this 
portion. However, in determining whether this portion of the species' 
range also meets the ``significance'' test under the SPR Policy, the 
ERA team concluded that the Mediterranean represents a small portion of 
the global range of the common thresher shark, and the loss of that 
portion would not result in the remainder of the species being 
endangered or threatened, particularly given the fact that there is no 
evidence to suggest the species makes trans-Atlantic migrations, and 
thus that other portions of the species' global population would be at 
risk from threats in the Mediterranean region. In particular, we did 
not find substantial evidence to indicate that the loss of this portion 
would result in a level of abundance for the remainder of the species 
to be so low or variable, that it would cause the species to be at a 
moderate or high risk of extinction due to environmental variation, 
anthropogenic perturbations, or depensatory processes. We also could 
not find any substantial evidence to suggest that the loss of the 
Mediterranean portion of its range would isolate the species to the 
point where the remaining populations would be at risk of extinction 
from demographic processes. We also found no evidence to suggest that 
the loss of genetic diversity from this portion would result in the 
remaining population lacking enough genetic diversity to allow for 
adaptations to changing environmental conditions. Although there is 
preliminary evidence of possible genetic partitioning between ocean 
basins, this was based on one study with a limited sample size (see 
Trejo, 2005_ENREF_224). Since common thresher sharks are globally 
distributed and highly mobile, we did not find that the loss of the 
Mediterranean portion would severely fragment and isolate the common 
thresher population to the point where individuals would be precluded 
from moving to suitable habitats or have an increased vulnerability to 
threats. Areas exhibiting source-sink dynamics, which could affect the 
survival of the species, were not evident in any part of the common 
thresher shark range. There is also no evidence that the Mediterranean 
portion of the range encompasses aspects that are important to specific 
life history events that other portions do not, where loss of the 
former portion would severely impact the growth, reproduction, or 
survival of the entire species. There is also little to no information 
regarding nursery grounds or other important habitats utilized by the 
species that could be considered limiting factors for the species' 
survival. In fact, we found evidence that there are likely reproductive 
grounds and nursery areas in all three major ocean basins. In other 
words, the viability of the species does not appear to depend on the 
productivity of the population or the environmental characteristics in 
the Mediterranean portion of the range. Overall, we did not find any 
evidence to suggest that this specific portion of the species' range 
has increased importance over any other with respect to the species' 
survival. As such, the Mediterranean region does not meet the 
significance criteria under the SPR policy. We could not identify any 
other portions of the common thresher shark range in which the species 
is in danger of extinction, or likely to become so in the foreseeable 
future, and thus our SPR analysis ends.

Final Determination

    Section 4(b)(1) of the ESA requires that NMFS make listing 
determinations based solely on the best scientific and commercial data 
available after conducting a review of the status of the species and 
taking into account those efforts, if any, being made by any state or 
foreign nation, or political subdivisions thereof, to protect and 
conserve the species. We have independently reviewed the best available 
scientific and commercial

[[Page 18998]]

information, including the petition, public comments submitted on the 
90-day finding (80 FR 11379; March 3, 2015), the status review report 
(Young et al., 2015), and other published and unpublished information, 
and we have consulted with species experts and individuals familiar 
with common thresher sharks. We considered each of the Section 4(a)(1) 
factors to determine whether it contributed significantly to the 
extinction risk of the species on its own. We also considered the 
combination of those factors to determine whether they collectively 
contributed significantly to the extinction risk of the species. As 
previously explained, we could not identify any portion of the species' 
range that met both criteria of the SPR policy. Although the 
Mediterranean region was identified as a portion of the range in which 
the common thresher has a higher risk of extinction due to concentrated 
threats, we could not identify this portion as ``significant.'' 
Additionally, we could not identify any other portion of the species' 
range in which the species is currently in danger of extinction or 
likely to become so in the foreseeable future. Therefore, our 
determination set forth below is based on a synthesis and integration 
of the foregoing information, factors and considerations, and their 
effects on the status of the species throughout its entire range.
    We conclude that the common thresher shark is not presently in 
danger of extinction, nor is it likely to become so in the foreseeable 
future, throughout all of its range. We summarize the factors 
supporting this conclusion as follows: (1) The species is broadly 
distributed over a large geographic range, with no barrier to 
dispersal; (2) there is no evidence of a range contraction and there is 
no evidence of habitat loss or destruction; (3) while the species 
possesses life history characteristics that increase its vulnerability 
to harvest, it has been found to be less susceptible to pelagic 
longline fisheries compared to other shark species (based on results 
from Ecological Risk Assessments), decreasing the chance of substantial 
fishing mortality from this fishery that operates throughout its range; 
(4) the best available information indicates that abundance is variable 
across the species' range, with reports of localized population 
declines but also evidence of stable and/or increasing abundance 
estimates; (5) based on the ERA team's assessment, while the current 
population size has likely declined from historical numbers, it is 
sufficient to maintain population viability into the foreseeable 
future; (6) the main threat to the species is fishery-related mortality 
from global fisheries; however, information on harvest rates is 
inconclusive due to poor species discrimination and significant 
uncertainties in the data, with the best available information 
indicating low utilization of the species (rare in tropical fisheries 
records in both the Western and Central Pacific and Indian Oceans as 
well as the South Atlantic, and rarely identified as present in several 
genetic tests of shark fins from markets throughout its range); (7) 
there is no evidence that disease or predation is contributing to 
increasing the risk of extinction of the species; (8) existing 
regulatory mechanisms throughout a large portion of the species' range 
appear effective in addressing the most important threats to the 
species (harvest); (9) there is no evidence that other natural or 
manmade factors are contributing to increasing the risk of extinction 
of the species; and, (10) while the global population has likely 
declined from historical numbers, there is no evidence that the species 
is currently suffering from depensatory processes (such as reduced 
likelihood of finding a mate or mate choice or diminished fertilization 
and recruitment success) or is at risk of extinction due to 
environmental variation or anthropogenic perturbations. Finally, and as 
previously described in the SPR analysis above, we determined that the 
species is not threatened or endangered in a significant portion of its 
range.
    Based on these findings, we conclude that the common thresher shark 
is not currently in danger of extinction throughout all or a 
significant portion of its range, nor is it likely to become so within 
the foreseeable future. Accordingly, the common thresher shark does not 
meet the definition of a threatened or endangered species, and thus, 
the common thresher shark does not warrant listing as threatened or 
endangered at this time.

Bigeye Thresher Shark (Alopias superciliosus)

Species Description

    The bigeye thresher shark (Alopias superciliosus) has a broad head, 
moderately long and bulbous snout, curved yet broad-tipped pectoral 
fins, distinctive grooves on the head above the gills, and large teeth. 
The first dorsal-fin midbase is closer to the pelvic-fin bases than to 
the pectoral-fin bases. The caudal tip is broad with a wide terminal 
lobe. While some of the above characteristics may be shared by other 
thresher shark species, diagnostic features separating this species 
from the other two thresher shark species (common and pelagic thresher) 
are their extremely large eyes, which extend onto the dorsal surface of 
the head, and the prominent notches that run dorso-lateral from behind 
the eyes to behind the gills. The body can be purplish grey or grey-
brown on the upper surface and sides, with grey to white coloring on 
its underside; however, unlike the common thresher, the light color of 
the abdomen does not extend over the pectoral fins and there is no 
white dot on the upper pectoral fin tips like those often seen in 
common threshers (Compagno, 2001).

Current Distribution

    The bigeye thresher shark is a large, highly migratory oceanic and 
coastal species of shark found throughout the world in tropical and 
temperate seas. In the western Atlantic (including the Gulf of Mexico), 
bigeye threshers can be found off the Atlantic coast of the United 
States (from New York to Florida), and in the Gulf of Mexico off 
Florida, Mississippi and Texas. They can also be found in Mexico (from 
Veracruz to Yucatan), Bahamas, Cuba, Venezuela, as well as central and 
southern Brazil. In the eastern Atlantic, bigeye threshers are found 
from Portugal to the Western Cape of South Africa, including the 
western and central Mediterranean Sea. In the Indian Ocean, bigeye 
threshers are found in South Africa (Eastern Cape and KwaZulu-Natal), 
Madagascar, Arabian Sea (Somalia), Gulf of Aden, Maldives, and Sri 
Lanka. In the Pacific Ocean, from west to east, bigeye threshers are 
known from southern Japan (including Okinawa), Taiwan (Province of 
China), Vietnam, between the Northern Mariana Islands and Wake Island, 
down to the northwestern coast of Australia and New Zealand, as well as 
American Samoa. Moving to the Central Pacific, bigeye threshers are 
known from the waters surrounding Wake, Marshall, Howland and Baker, 
Palmyra, Johnston, Hawaiian Islands, Line Islands, and between 
Marquesas and Galapagos Islands. Finally, in the Eastern Pacific, 
bigeye threshers occur from Canada to Mexico (Gulf of California) and 
west of Galapagos Islands (Ecuador). They are also possibly found off 
Peru and northern Chile (Compagno, 2001; Ebert et al., 2014).

Habitat Use and Movement

    Bigeye thresher sharks are found in a diverse spectrum of 
locations, including in coastal waters over continental shelves, on the 
high seas in the epipelagic zone far from land, in deep

[[Page 18999]]

waters near the bottom on continental slopes, and sometimes in shallow 
inshore waters. They are an epipelagic, neritic, and epibenthic shark, 
ranging from the surface and in the intertidal to at least 500 m deep, 
and have even been recorded as deep as 723 m (Nakano et al., 2003), but 
mostly occur in depths below 100 m (Compagno, 2001). Bigeye threshers 
are known to endure colder water and remain longer in deeper waters 
than many other pelagic sharks (Gruber and Compagno, 1981; Fernandez-
Carvalho et al., 2015). Like common threshers, bigeye thresher sharks 
are also known to make daily diel vertical migrations, spending most of 
their day below the thermocline, and most of the night in the mixed 
layer and upper thermocline (Nakano et al., 2003; Weng and Block, 2004; 
Kohin et al., 2006; Stevens et al., 2009; Musyl et al., 2011). In the 
Marshall Islands, Cao et al. (2011) identified a preferred optimum 
swimming depth of 240-360 m, water temperature of 10-16 [deg]C, 
salinity of 34.5-34.7 ppt and dissolved oxygen range of 3.0-4.0 ml/l 
for bigeye threshers. Nakano et al. (2003) recorded the deepest dive to 
date in the Eastern Tropical Pacific, extending the known depth 
distribution for bigeye thresher to 723 m.
    In the Atlantic, mark/recapture data (number tagged = 400 and 
number recaptured = 12) from the NMFS CSTP between 1963 and 2013 showed 
that the range of movement for the bigeye thresher was much larger than 
for the common thresher (Kohler, 1998; Kohler and Turner, 2001; NMFS, 
unpublished data), with a maximum straight-line distance travelled of 
2,067 nmi (3,828 km; NMFS, unpublished data). This transatlantic 
movement was from a shark tagged in 1984 by a NMFS shark biologist 565 
nmi (1046 km) southwest of the Cape Verde Islands off the west coast of 
Africa and recaptured in 1994 by a commercial longliner 19 nmi (35 km) 
off the Venezuelan coast (NMFS, unpublished data), confirming that this 
species is highly migratory.

Diet

    Bigeye threshers have larger teeth than common threshers and feed 
on a wider variety of prey, including small to medium sized pelagic 
fishes (e.g., lancetfishes, herring, mackerel and small billfishes), 
bottom fishes (e.g., hake) and cephalopods (e.g., squids). Thus, the 
bigeye thresher appears to be an opportunistic feeder, foraging on 
diverse species covering a broad range of habitats, whereas niche 
separation is more apparent for common threshers (Preti et al. 2008). 
The arrangement of the eyes, with keyhole-shaped orbits extending onto 
the dorsal surface of the head, suggest that this species has a dorsal/
vertical binocular field of vision (unlike other threshers), which may 
be related to fixating on prey and striking them with its tail from 
below (FAO, 2015). Based on a study at the NMFS SWFSC, the top five 
prey species, in order, are barracudinas, Pacific hake, Pacific saury, 
Pacific mackerel, and northern anchovy. At least eight cephalopod 
species were also observed, although most species were found in only a 
few stomachs (Preti et al., 2008).

Reproduction

    The bigeye thresher has the slowest growth rate and is the least 
productive compared to the other Alopias species. It reaches maturity 
at a later age than the common thresher, about 10 years for males and 
13 years for females. In terms of size, females attain maturity 
generally around 332-355 cm TL while males reach maturity at smaller 
sizes (generally around 270-288 cm TL) (see Table 2 in Young et al., 
2015). Like other thresher species, the reproductive mode of bigeye 
thresher is aplacental viviparity with oophagy; however, bigeye 
threshers usually bear only two pups per litter--one per uterus 
(although cases of up to four embryos may occur), resulting in an 
extremely low fecundity. The gestation period may be 12 months long, 
but remains uncertain due to a lack of birthing seasonality data (Liu 
et al., 1998). However, there have been some observations and 
hypotheses regarding potential birthing seasons and nursery areas of 
bigeye thresher sharks from various parts of its range, including 
summer, fall, and winter in the Florida Straits. Another nursery for 
this species may exist in nearshore Cuban waters, as many small 
juveniles and females with full-term litters have been observed there 
(Guitart, 1975 cited in Camhi et al., 2008). Moreno and Mor[oacute]n 
(1992) concluded that birth occurs over a protracted period from autumn 
to winter in the Strait of Gibraltar. More recently, Fernandez-Carvalho 
et al. (2015) observed the presence of large embryos (closer to the 
size at birth) in October/November in the northeast Atlantic and in 
March in the Southwest Atlantic, which seems to suggest that birth may 
be taking place during late summer and autumn in both hemispheres. This 
corroborates what has been previously suggested for both regions, 
particularly by Moreno and Mor[oacute]n (1992) for the Northeast, that 
a nursery area for this species exists off the southwestern Iberian 
Peninsula based on the records of several pregnant females. In fact, 
Fernandez-Carvalho et al. (2015) hypothesize that such an area not only 
exists, but possibly extends farther south, into the tropical Northeast 
Atlantic and equatorial waters closer to the African continent. This 
may be validated by the fact that smaller and mainly juvenile specimens 
tended to be captured in the tropical Northeast and equatorial waters, 
as well as pregnant females both in mid- and late-term stages. Another 
cluster of pregnant females was recorded in the Southwest Atlantic, 
some close to the Rio Grande Rise and a few inside the Uruguayan EEZ, 
suggesting these areas may also be nurseries for this species in the 
South Atlantic. This was previously suggested in a study by Amorim et 
al. (1998), who also reported the presence of pregnant females in this 
area. In contrast, a different reproduction and birth seasonality may 
exist in the Pacific Ocean, where Matsunaga and Yokawa (2013) reported 
that neonates (<80 cm pre-caudal length) were caught mainly during 
winter and spring in an area between 10 and 15 [deg]N.

Size and Growth

    Bigeye threshers have a maximum estimated age of about 20 years, 
and can grow to a maximum total length of 504 cm (TL) depending on sex 
and geographic location. Growth rates are also different depending on 
geographic location. Male bigeye thresher sharks are thought to grow 
slightly faster than females (with a growth coefficient, k, of 0.088/
year for males and 0.092/year for females in the Northwest Pacific and 
0.18/year for males and 0.06/year for females in the eastern Atlantic) 
but reach a smaller asymptotic size (206 cm FL for males versus 293 cm 
FL for females) (Liu et al., 1998; Fernandez-Carvalho et al., 2011). 
Using life history parameters from the eastern central Atlantic, 
Cort[eacute]s et al. (2012) estimated productivity of the bigeye 
thresher shark, determined as intrinsic rate of population increase 
(r), to be 0.009 per year (median). Overall, the best available data 
indicate that the bigeye thresher shark is a long-lived species (at 
least 20 years) and can be characterized as having low productivity 
(based on the Food and Agriculture Organization of the United Nations 
(FAO) productivity indices for exploited fish species, where r < 0.14 
is considered low productivity), making them generally vulnerable to 
depletion and potentially slow to recover from overexploitation.

Current Status

    Bigeye thresher sharks can be found worldwide, with no present 
indication of a range contraction. Although they

[[Page 19000]]

are generally not targeted, they are caught as bycatch in many global 
fisheries, including bottom and pelagic longline tuna and swordfish 
fisheries, purse seine fisheries, coastal gillnet fisheries, and 
artisanal fisheries. Bigeye thresher sharks are more commonly utilized 
for their meat than fins, as they are a preferred species for human 
consumption (although not as preferred as the common thresher); 
however, they are also valuable as incidental catch for the 
international shark fin trade.
    In 2009, the IUCN considered the bigeye thresher shark to be 
Vulnerable globally, based on an assessment by Amorim et al. (2009) and 
its own criteria (A2bd), and placed the species on its ``Red List.'' As 
noted previously, under criteria A2bd, a species may be classified as 
Vulnerable when its ``observed, estimated, inferred or suspected'' 
population size is reduced by 30 percent or more over the last 10 
years, or over a 3-generation period, whichever is the longer, and 
where the causes of the reduction may not have ceased or may not be 
understood or may not be reversible, based on an index of abundance 
appropriate to the taxon and/or the actual or potential levels of 
exploitation. The IUCN justification for the categorization is based on 
the bigeye thresher's suspected declining populations as result of a 
combination of slow life history characteristics (hence low capacity to 
recover from moderate levels of exploitation), and high levels of 
largely unmanaged and unreported mortality in target and bycatch 
fisheries. As a note, the IUCN classification for the bigeye thresher 
shark alone does not provide the rationale for a listing recommendation 
under the ESA, but the classification and the sources of information 
that the classification is based upon are evaluated in light of the 
standards on extinction risk and impacts or threats to the species.

Distinct Population Segment Analysis

    The petition to list the bigeye thresher shark requested NMFS to 
list it throughout its range, or alternatively, as DPSs should NMFS 
find they exist. The ERA team was asked to examine the best available 
data to determine whether DPSs may exist for this species. The 
petition, itself, did not provide any information regarding potential 
DPSs of bigeye thresher shark, aside from requesting that NMFS consider 
using the regions/populations as outlined and delimited in the petition 
(i.e., Northwest and Western Central Atlantic, Southwest Atlantic, 
Mediterranean Sea and Eastern Atlantic, Indo-West Pacific, and Eastern 
Central Pacific). The petition did not otherwise provide support to 
identify any DPSs of bigeye thresher shark. As previously noted, to 
meet the definition of a DPS, a population must be both discrete from 
other populations of the species and significant to the species as a 
whole (61 FR 4722; February 7, 1996). The petition did not provide 
biological evidence to support the existence of any ``subpopulations'' 
nor did the petition propose any boundaries for DPSs. Additionally, the 
petition did not describe in any detail the ways in which different 
management relating to international governmental boundaries may 
delineate the species into boundaries aligning with the suggested 
regions/populations. Specific gaps in management or intergovernmental 
boundaries were not described as they relate to any of the suggested 
regions/populations. In our review of the best available data, we were 
also unable to find information to define any DPSs as discrete on 
biological grounds. We found only two preliminary studies to suggest 
population structure of the bigeye thresher shark. Trejo (2005) 
examined mitochondrial control region DNA, which demonstrated 
significant population structure between most pairwise comparisons, but 
the sample sizes were extremely low, and thus the results could not be 
interpreted with confidence. The data results support shallow 
population structure between Indo-Pacific and Atlantic populations, but 
not among populations spanning the entire Indo-Pacific Ocean (Trejo, 
2005). In a genetic analysis by Naylor et al. (2012), little difference 
was seen among nine specimens spanning much of the global distribution 
of the species. Based on the preliminary nature of these data, and low 
sample size throughout the studies, these results cannot be relied upon 
to divide the bigeye thresher shark into any discrete populations. In 
our review of the best available data, we were also unable to find 
information to define any DPSs as discrete based on any other physical, 
physiological, ecological, or behavioral factors or based on 
differences in control of exploitation, management of habitat, 
conservation status, or regulatory mechanisms across any international 
governmental boundaries that would be significant in light of potential 
threats to the species. Thus, we concluded that the best available 
information does not indicate that any population segment of the bigeye 
thresher shark would qualify as a DPS under the DPS policy. As such, we 
conducted the extinction risk analysis on the global bigeye thresher 
shark population.

Assessment of Extinction Risk

    Please refer back to the Assessment of Extinction Risk section for 
the common thresher for statutory definitions and methods of the 
extinction risk assessment. In terms of determining a reasonable 
foreseeable future timeframe for the bigeye thresher, the ERA team 
first considered the life history of the species. Longevity of the 
bigeye thresher is estimated to be about 25 years. Generation time, 
which is defined as the time it takes, on average, for a sexually 
mature female bigeye thresher shark to be replaced by offspring with 
the same spawning capacity, is estimated to be approximately 17.8 
years. As a late-maturing species (like the common thresher), with 
relatively slow growth rates and low productivity, it would likely take 
more than a generation time for any conservative management action to 
be realized and reflected in population abundance indices. As 
previously described, this is supported by the fact that we have a 
well-documented example of how these species respond to intense fishing 
pressure, and the time required for the initial implementation of 
regulatory measures to be reflected in population abundance indices 
(refer back to the common thresher Assessment of Extinction Risk 
section for more details). Thus, given that the bigeye thresher has 
lower productivity than the common thresher, the ERA team assumed that 
the time required to observe changes in abundance indices would be 
longer, and would also similarly comport with 3 generation times (i.e., 
50 years). The ERA team then discussed whether they could confidently 
predict the impact of threats on the species out to 50 years and agreed 
that since the main threats to the species were likely fisheries and 
the regulatory measures that manage these fisheries, they had the 
background knowledge and expertise to confidently predict the impact of 
these threats on the biological status of the species within this 
timeframe. For the foregoing reasons, the ERA team concluded, and we 
agree, that a biologically reasonable foreseeable future timeframe 
would be 50 years for the bigeye thresher.

Evaluation of Demographic Risks

Abundance

    Currently, there is a lack of reliable species-specific global 
population size estimates, population assessments, and trends in 
abundance for the bigeye thresher shark. As previously noted, using a 
thresher complex or other thresher species as a proxy for bigeye 
thresher abundance could be erroneous because of the differences in the 
species'

[[Page 19001]]

distributions as well as the proportions they make up in commercial 
catches. In most areas showing overall declines in Alopiids, it is 
uncertain which thresher species the declines are more likely 
attributable to, although most declines are likely attributable to 
either the bigeye or pelagic thresher rather than common threshers, 
with the exception of the Mediterranean. Additionally, there are also 
long-term misidentification issues between thresher sharks, which means 
historical data regarding thresher catch is likely not entirely 
accurate. The ERA team expressed some concern regarding the bigeye 
thresher shark's global abundance, particularly given that the species 
likely experienced localized population declines over the past few 
decades. Given the lack of data, and the fact that most of the 
available information is not specific to bigeye thresher, the extent of 
the declines and current status of the global population are unclear. 
However, some information, including species-specific analyses of 
standardized observer data from the Northwest Atlantic and Hawaii, 
provide some insight into the current abundance levels of the species.
    Bigeye thresher shark populations have likely exhibited historical 
declines in abundance relative to virgin biomass levels, but 
information regarding the magnitude of these declines is poor. In areas 
where more recent indicators of abundance for bigeye thresher are 
available (i.e., standardized CPUE trends), abundance trends are highly 
variable. In the Northwest Atlantic, it is likely that the bigeye 
thresher population suffered a significant historical decline (refer 
back to the discussion of Baum et al. (2003) and Cort[eacute]s (2007) 
in the common thresher Demographic Risk Assessment--Abundance section); 
however, the ERA team questioned the magnitude of these declines, 
noting several issues with the available information, including the 
following: The data used were not species-specific, the time series 
ended in 2006, and the data were based on fisheries logbooks rather 
than observer data. The ERA team determined that observer data is 
likely more representative for bycatch species; thus, in order to 
determine species-specific abundance trends of bigeye thresher in the 
Northwest Atlantic, the ERA team analyzed the available species-
specific observer data from the U.S. Northwest Atlantic Pelagic 
Longline Fishery from 1992-2013. From this analysis, the ERA team 
determined that although the population of bigeye thresher shark in 
this area suffered a historical decline, the population has likely 
stabilized since 1990.
    In the Western and Central Pacific, where bigeye threshers are most 
commonly observed and likely most abundant, trends in abundance are 
variable. As described earlier in the common thresher Abundance 
section, much of the fisheries data from this region are for the 
thresher complex (all three Alopias spp.), thus making it difficult to 
discern abundance trends for any one species in particular. In order to 
glean species-specific abundance trends for bigeye thresher, the ERA 
team conducted an analysis of species-specific observer data from the 
Hawaii-based pelagic longline fishery, which indicates that abundance 
of bigeye thresher has been relatively stable since 1994, and even 
potentially increasing in recent years. In contrast, fisheries data 
from the rest of the Western and Central Pacific region suggest 
thresher abundance may be on a decline, particularly in the last few 
years (Rice et al., 2015). However, the latter data from the rest of 
the Western and Central Pacific is not specific to bigeye thresher, and 
rather analyzes the thresher complex (all three Alopias spp.). As such, 
interpreting these data is difficult, particularly since the second 
most common species reported is the general ``thresher shark'' 
category. Given that the bigeye thresher is typically the dominant 
thresher species in catch records from this region combined with its 
more tropical distribution, the ERA team made the assumption that the 
trends from the Western and Central Pacific are likely reflective of 
bigeye thresher. However, even given this assumption, the ERA team 
determined, and we agree, that the potential population decline in this 
region in the last few years, combined with a stable and potentially 
increasing abundance trend of bigeye thresher in the Central Pacific 
since 1994, indicates that the potential population decline of bigeye 
thresher is not Pacific-wide. Thus, the best available information 
indicates that the species' current level of abundance in the Western 
and Central Pacific is spatially variable, but not likely so low such 
that it places the species at a high risk of extinction throughout its 
global range, now or in the foreseeable future.
    Abundance information from other portions of the species' range is 
relatively poor and unreliable or lacking altogether. In areas where 
data are lacking (e.g., South Atlantic, Indian Ocean) it was difficult 
to discern if the population is stable or in decline. In a recent 
proposal developed by Sri Lanka to list all three thresher species 
under CITES Appendix II, a population decline of 83 percent was 
inferred for the Indian Ocean based on a study conducted in the Eastern 
and Central Pacific (Ward and Myers, 2005), because there is currently 
no confirmed stock separation between the Indian and Pacific Ocean 
stocks of the species. However, as previously described in this 
finding, the ERA team identified several caveats regarding the Ward and 
Myers (2005) study, including differences in survey locations as well 
as data types used (e.g., fishery-independent vs. fishery-dependent) 
and seriously questioned the conclusions regarding the magnitude of 
decline for the thresher complex in this region. However, given the 
high fishing pressure in the Indian Ocean, coupled with the species' 
high bycatch-related mortality rates and low productivity (IOTC, 2014), 
the ERA team concluded that it is likely the species is experiencing 
some level of population decline in this region that may be similar to 
declines in other portions of the species' range; nevertheless, we do 
not have enough information to determine the magnitude of this decline 
and whether this decline is significantly contributing to the 
extinction risk of the global population.
    In the South Atlantic, standardized CPUE data indicate that bigeye 
thresher abundance may have declined only slightly from 1978 to 2006 
(Mourato et al., 2008); however, the available CPUE time series ended 
in 2006 and best available information indicates that the main fishery 
catching bigeye threshers (the Brazilian Santos longline fishery) 
underwent several operational changes, including a shift in effort to 
more temperate waters, which may have reduced fishing pressure on 
bigeye thresher in this portion of its range. We could not find any 
other reliable abundance indices that indicate bigeye thresher has 
experienced a significant population decline in the Southwest Atlantic 
region.
    Overall, there is no evidence to suggest that present abundance 
levels are so low, such that depensatory processes are at work. As 
previously noted, although it is likely that the bigeye thresher shark 
has experienced declines of varying magnitudes throughout its range due 
to fishing mortality, recent relative abundance data included in the 
status review report (Young et al., 2015) suggest that abundance trends 
are highly variable throughout the species' global range, with 
populations increasing, stable, slightly declining, or showing no clear 
trend. We noted that bigeye threshers are still captured regularly 
throughout their range and the range does not

[[Page 19002]]

appear to have contracted. Thus, based on the best available 
information, we conclude that the current abundance of bigeye thresher 
throughout its range is not contributing significantly to the species' 
risk of extinction, such that the species has a high risk of extinction 
throughout its global range, now or in the foreseeable future.

Growth Rate/Productivity

    Similar to abundance, the ERA team expressed some concern regarding 
the effect of the bigeye thresher shark's growth rate and productivity 
on its risk of extinction. Bigeye thresher sharks exhibit life-history 
traits and population parameters that are on the low end of the 
spectrum among other shark species. The estimated growth coefficients 
confirm that the bigeye thresher is generally a slow-growing species. 
Relative to other thresher species, the bigeye thresher shark is the 
least fecund and productive, with a low intrinsic rate of population 
increase (r = 0.009 year-1; Cort[eacute]s et al., 2012). 
These demographic parameters place bigeye thresher shark towards the 
slower growing sharks along the ``fast-slow'' continuum of population 
parameters calculated for 38 species of sharks (see Appendix 2 of 
Cort[eacute]s (2002)), which means this species generally has a low 
potential to recover from exploitation. In addition, based on several 
Ecological Risk Assessments, bigeye threshers have been found to be the 
most susceptible to pelagic longline fisheries in the Atlantic and 
Indian Oceans when compared to other shark species. Based on the best 
available information, including the fact that most species of 
elasmobranchs require many years to mature and have relatively low 
fecundity compared to teleosts, these life history characteristics 
could pose a risk to this species in combination with threats that 
reduce its abundance, such as overutilization.

Spatial Structure/Connectivity

    Like the common thresher, habitat characteristics that are 
important to the bigeye thresher are unknown, as are nursery areas. 
There is currently no evidence of female philopatry, the species is 
highly mobile, and there is little known about specific migration 
routes. It is also unknown if there are source-sink dynamics at work 
that may affect population growth or species' decline. Thus, based on 
the best available information, there is insufficient information to 
support the conclusion that spatial structure and connectivity pose 
significant risks to this species.

Diversity

    Similar to the common thresher, the ERA team concluded, and we 
agree, that the current level of information regarding the bigeye 
thresher shark's diversity is either unavailable or unknown, such that 
the contribution of this factor to the extinction risk of the species 
cannot be determined at this time. Currently, there is no evidence to 
suggest the species is at risk due to a substantial change or loss of 
variation in genetic characteristics or gene flow among populations.

Summary of Factors Affecting the Bigeye Thresher Shark

    As described previously, section 4(a)(1) of the ESA and NMFS 
implementing regulations (50 CFR 424.11(c)) state that we must 
determine whether a species is endangered or threatened because of any 
one or a combination of the following factors: The present or 
threatened destruction, modification, or curtailment of its habitat or 
range; overutilization for commercial, recreational, scientific, or 
educational purposes; disease or predation; the inadequacy of existing 
regulatory mechanisms; or other natural or manmade factors affecting 
its continued existence. The ERA team evaluated whether and the extent 
to which each of the foregoing factors contributed to the overall 
extinction risk of the global bigeye thresher shark population. This 
section briefly summarizes the ERA team's findings and our conclusions 
regarding threats to the common thresher shark. More details can be 
found in the status review report (Young et al., 2015).

The Present or Threatened Destruction, Modification, or Curtailment of 
Its Habitat or Range

    The ERA team did not identify habitat destruction as a potential 
threat to the bigeye thresher shark. As described earlier (see Species 
Description--Movement and Habitat Use section) the bigeye thresher 
shark is a large, highly migratory oceanic and coastal species of shark 
found throughout the world in tropical and temperate seas (Compagno, 
1984). Bigeye thresher sharks are found in a diverse spectrum of 
locations, including in coastal waters over continental shelves, on the 
high seas in the epipelagic zone far from land, in deep waters near the 
bottom on continental slopes, and sometimes in shallow inshore waters. 
They range from the surface and in the intertidal to at least 500 m 
deep, and have even been recorded as deep as 723 m (Nakano et al., 
2003), but mostly occur in depths below 100 m (Compagno, 2001); 
however, little else is known regarding specific habitat preferences or 
characteristics.
    As previously described, the MSA requires NMFS to identify and 
describe EFH in FMPs, minimize the adverse effects of fishing on EFH, 
and identify actions to encourage the conservation and enhancement of 
EFH in the U.S. EEZ. Results from the two previously described NMFS-
funded cooperative survey programs indicate the importance of coastal 
waters off the Atlantic east coast, from Maine to the Florida Keys, 
central Gulf of Mexico and localized areas off of Puerto Rico and the 
U.S. Virgin Islands (NMFS, 2009). As a side note, insufficient data are 
available to differentiate EFH by size classes in the Atlantic for the 
bigeye thresher shark; therefore, EFH is the same for all life stages. 
Since bigeye thresher shark EFH is defined as the water column or 
attributes of the water column, NMFS determined that there are minimal 
or no cumulative anticipated impacts to the EFH from gear used in U.S. 
HMS and non-HMS fisheries, basing its finding on an examination of 
published literature and anecdotal evidence (NMFS, 2006).
    The bigeye thresher population off California and Oregon appears to 
be predominantly adult males (71 percent of observed catches are mature 
males), which range north to Oregon, and immature females, which 
primarily occur south of Monterey Bay and in the Southern California 
Bight. Essential Fish Habitat is described for two age classes: Late 
juveniles/subadults and adults. Neonates/early juveniles (~90 to 115 cm 
FL, 0 to 2 and 3 year olds) are not known to occur in the U.S. West 
Coast EEZ, thus EFH is not defined for this size class. For late 
juveniles/subadults (>115 cm FL and <155 cm FL males and <189 cm FL 
females), EFH is described as coastal and oceanic waters in epi- and 
mesopelagic zones from the U.S.-Mexico border north to 37[deg] N. 
latitude off Davenport, California, South of 34[deg] N. latitude from 
the 100 fm (183 m) isobath to the 2,000 fm (3,568 m) isobaths and north 
of 34[deg] N. from the 800 fm (1,463 m) isobath out to the 2,200 fm 
(4,023 m) isobath. For adults (>154 cm FL males and >188 cm FL females) 
EFH is described as coastal and oceanic waters in epi-and mesopelagic 
zones from the U.S.-Mexico border north to 45[deg] N. latitude off 
Cascade Head, Oregon. In southern California EFH is south of 34[deg] N. 
latitude from the 100 fm (183 m) isobath out to the 2,000 fm (3,568 m) 
isobath and North of 34[deg] N. latitude from the 800 fm (1,463 m) 
isobath out to the outer EEZ boundary.

[[Page 19003]]

In the U.S. Western Pacific, including Hawaii, American Samoa, Guam, 
and the Commonwealth of the Northern Mariana Islands, EFH for bigeye 
thresher is described identically to common thresher (refer back to the 
common thresher The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range section of this finding).
    Likewise, bigeye thresher shark habitat in other parts of its range 
is assumed to be similar to that in the Northwest Atlantic and Gulf of 
Mexico, comprised of open ocean environments occurring over broad 
geographic ranges and characterized primarily by the water column 
attributes. As such, large-scale impacts, such as global climate 
change, that affect ocean temperatures, currents, and potentially food 
chain dynamics, may pose a threat to this species. Studies on the 
impacts of climate change specific to thresher sharks have not been 
conducted; however, there are a couple of studies on other pelagic 
shark species that occur in the range of the bigeye thresher shark 
(refer back to the common thresher The Present or Threatened 
Destruction, Modification, or Curtailment of Its Habitat or Range 
section for a summary of relevant climate change studies in which 
pelagic sharks have variable vulnerability to the effects of climate 
change). However, like the common thresher, the bigeye thresher shark 
is highly mobile throughout its range; and, although there is very 
little information on habitat use and pupping and nursery areas, there 
is no evidence to suggest its access to suitable habitat is restricted. 
Additionally, bigeye threshers are likely more confined by temperature 
and prey distributions than a particular habitat type. The highly 
migratory nature of bigeye threshers gives them the ability to shift 
their range or distribution to remain in an environment conducive to 
their physiological and ecological needs. Thus, it is very unlikely 
that the loss or degradation of any particular habitat type would have 
a substantial effect on the global bigeye thresher population. Further, 
there is currently no evidence to suggest a range contraction based on 
habitat degradation for the bigeye thresher shark. As a result, the ERA 
team concluded, and we agree, that the effect that habitat destruction, 
modification, or curtailment is having on the species' extinction risk 
is low. Therefore, based on the best available information, we conclude 
that current evidence does not indicate that there exists a present or 
threatened destruction, modification, or curtailment of the bigeye 
thresher shark's habitat or range.

Overutilization for Commercial, Recreational, Scientific or Educational 
Purposes

    Like the common thresher, the bigeye thresher is also considered a 
valuable bycatch species, which, when combined with its high at-vessel 
mortality rates and low productivity, makes this species more 
susceptible to overutilization. The ERA team assessed three different 
factors that may contribute to the overutilization of the bigeye 
thresher shark: Bycatch in commercial fisheries (including at-vessel 
and post-release mortality rates), recreational fisheries, and the 
global shark trade (including the trade of both bigeye thresher fins 
and meat). Similar to common thresher sharks, bigeye thresher sharks 
are caught as bycatch in many global fisheries, including bottom and 
pelagic longline fisheries, purse seine fisheries, coastal gillnet 
fisheries, and artisanal fisheries; however, as a primarily pelagic and 
tropical species (in contrast to the common thresher's more coastal and 
temperate distribution), the bigeye thresher shark is relatively common 
in the catches of tropical fisheries, particularly in the Western and 
Central Pacific and Indian Oceans. It is also relatively common in 
catches of fisheries operating in the Northwest and South Atlantic. 
Though it is generally not a target species in commercial fisheries, 
the bigeye thresher shark is valued for both its meat and fins, and is 
therefore valued as incidental catch for the international shark trade 
(Clarke et al., 2006a; Dent and Clarke, 2015).
    As noted previously in the Evaluation of Demographic Risks--
Abundance section, there is very little information on the historical 
abundance, catch, and trends of bigeye thresher sharks, with the 
exception of U.S. data from the Northwest Atlantic and Central Pacific 
(i.e., Hawaii). As described previously, although more countries and 
RFMOs are working towards better reporting of fish catches down to 
species level, catches of bigeye threshers have gone and continue to go 
unrecorded in many countries. Additionally, many catch records that do 
include thresher sharks do not differentiate between the Alopias 
species or shark species in general, and if they do, they are often 
plagued by species misidentifications. These numbers are also likely 
under-reported in catch records, as many records do not account for 
discards or they reflect dressed weights instead of live weights. Thus, 
the lack of catch data for bigeye thresher sharks makes it difficult to 
estimate rates of fishing mortality or conduct detailed quantitative 
analyses of the effects of fishing on bigeye thresher populations.
    On the U.S. West Coast, utilization of bigeye thresher shark is 
likely minimal. Bigeye threshers sometimes co-occur with common 
threshers as incidental catch, but they are generally more prevalent 
offshore, especially north of Point Conception. The first reported 
catch within the U.S. West Coast EEZ occurred in 1963 when a bigeye 
thresher was taken in a set gillnet in southern California. Although it 
is now a regular incidental species in the drift net fishery (NMFS, 
2009), it is estimated that bigeye threshers comprise approximately 
only nine percent of the total thresher catch. Overall, bigeye thresher 
represents a minor component of U.S. West Coast fisheries; individuals 
taken within the management area are thought to be on the edges of 
their habitat ranges, and they are presumably not overexploited, at 
least locally (PFMC, 2003). Additionally, regulations to control for 
overutilization of common threshers in this region (described 
previously) would also confer benefits to the bigeye thresher shark, 
which is evidenced by the similar trajectories of West Coast commercial 
landings of both species.
    Farther south in the Eastern Pacific, the level of utilization of 
bigeye thresher is unclear, as there is currently very little 
information regarding the status of bigeye thresher in the Eastern 
Pacific. Bigeye threshers are known bycatch in purse-seine and longline 
fisheries operating in this region. In 2005, bigeye thresher 
represented the most incidentally caught shark species in the Korean 
longline fishery operating in the Eastern Pacific (between 1[deg]48' S. 
~7[deg]00' S. and 142[deg]00' ~149[deg]13' W.), comprising 12.8 percent 
of the total shark catch (Kim et al., 2006). The bigeye thresher is 
also the most prevalent thresher species caught as bycatch in purse-
seine fisheries operating in the Eastern Pacific. As previously 
described, thresher sharks (Alopias spp.) collectively represented 
approximately three percent of the species observed during the Shark 
Characteristics Sampling Program, with bigeye threshers comprising one 
percent of the catch, and unidentified threshers representing 0.7 
percent. Thresher bycatch in this fishery increased from 9 mt in 2010 
to 17 mt in 2011, and has remained stable between 10-11 mt since.
    Bigeye threshers are also reported in fisheries records from the 
principal port of Manta, Ecuador; however, they comprise a minor 
portion of the total shark catch and even the total thresher

[[Page 19004]]

catch. In fact, the pelagic thresher is the dominant thresher species 
landed in Ecuador, comprising up to 92 percent of thresher shark 
landings (Reardon et al., 2009), and representing 36 percent of the 
total shark catch. In contrast, the bigeye thresher comprises 
approximately 3 percent of the total shark catch in Ecuador (Amorim et 
al., 2009). Thus, while Carr et al. (2013) reported that bigeye 
threshers and blue sharks comprised 87 percent of shark fins in a 
seizure of illegal fins from the Galapagos Marine Reserve, given that 
64 percent of the thresher sharks from this catch had their heads 
removed, and genetic testing was not conducted to identify to species, 
there is some uncertainty as to whether all of the sharks were actually 
bigeye thresher. It is possible that some of the thresher sharks 
illegally taken were misidentified pelagic threshers. Thus, while 
bigeye thresher sharks are somewhat prevalent as bycatch in various 
fisheries in the Eastern Pacific Ocean, they seemingly comprise a 
relatively small portion of the total shark catch in several areas. 
Therefore, we conclude that overutilization is not likely occurring in 
this portion of the species' range, such that the species is 
experiencing an increased risk of extinction throughout its global 
range.
    In the Western and Central Pacific, bigeye threshers are regularly 
caught as bycatch in longline fisheries throughout the region. Longline 
fishing effort in this region has steadily increased since 1995 
primarily in the South Pacific, and nearly half the effort occurs in 
tropical and equatorial waters where bigeye threshers have shown the 
highest CPUEs (Matsunaga & Yokawa, 2013; Rice et al., 2015). Several 
analyses of fisheries data are available from the Western and Central 
Pacific; however, as previously mentioned, most of the information 
available is for the thresher complex, with the exception of observer 
data from the Hawaii-based pelagic longline fishery. Bigeye thresher 
sharks are the third most frequently caught elasmobranch in Hawaii tuna 
fisheries and the most commonly encountered thresher species in the 
observer data. The Hawaii-based longline fishery has observed an 
increase in the number of bigeye threshers caught as bycatch on tuna 
targeted trips. While participation, number of hooks, and number of 
tuna targeted trips have been slowly increasing since 2010 (PIFSC, 
2014), standardized CPUE derived from observer data indicates that 
abundance of bigeye thresher has been relatively stable since 1994, 
with a potentially substantial increase in recent years. Based on this 
information, the ERA team concluded, and we agree, that the bigeye 
thresher shark population appears relatively stable in this region of 
the Central Pacific Ocean.
    The bigeye thresher shark appears to be an important species in 
other longline fisheries of the Western and Central Pacific as well. 
Some reliable fisheries data from Japanese longline observer data 
indicate that bigeye thresher was the second most commonly caught shark 
species from 1992-2006, comprising 10.9 percent of the total shark 
catch (Matsunaga and Yokawa, 2013). Catch estimates indicate that 
removals have been stable over the last decade, and some analyses 
indicate slight increases in catch rates of thresher sharks in certain 
areas, although no clear temporal trend was detected (Clarke, 2011; 
Lawson, 2011). The bigeye thresher is also an important species in 
Taiwanese longline fisheries targeting tuna, comprising approximately 
five percent of the total shark catch (Liu and Tsai, 2011). Although 
catches of bigeye threshers have increased over time in Taiwanese 
longline fisheries, information regarding corresponding effort is not 
available to discern abundance trends. As previously discussed, bigeye 
thresher appears to be a common bycatch species in RMI longline 
fisheries, with 1,636 bigeye thresher sharks caught from 2005-2009 
(Bromhead et al. 2012); however, we could not discern any abundance 
trends from these data.
    As described previously in the common thresher Overutilization for 
Commercial, Recreational, Scientific or Educational Purposes section, 
the most recent standardized CPUE data from 2002-2014 for the Western 
and Central Pacific based on data holdings of the SPC, show a 
decreasing trend for the thresher complex from 2011-2013 (Rice et al., 
2015). While the last 3 years of both the standardized and nominal 
thresher CPUEs show a decline, the standardized CPUE from the thresher 
complex is difficult to interpret, as the second most commonly reported 
thresher species is the general ``thresher shark'' category. 
Additionally, while it appears the thresher shark complex is declining 
sharply at the last data point, this is based on relatively few data, 
which may not be robust and likely exaggerates the trend in the last 
year. In terms of biological indicators, the majority of observed 
thresher sharks occurred in a region of the Central Pacific just south 
of Hawaii, where the lengths of both male and female sharks were 
relatively stable throughout the time period. Overall, despite 
increasing fishing pressure over the past 20 years, focused 
predominantly in tropical areas where all life stages of bigeye 
thresher would likely occur (including potential nursery areas), recent 
available abundance indices have not shown any significant or ongoing 
population decline that would be cause for concern. Based on this 
information, the ERA team did not deem the declining trend in the last 
3 years to be so significant to conclude that overutilization is 
occurring throughout the entirety of the Western and Central Pacific. 
The ERA team emphasized, and we agree, that the present level of 
fishing pressure on bigeye thresher in this region is highly variable, 
both spatially and temporally, as evidenced by increasing trends in 
Hawaiian fisheries compared to slightly declining trends for the rest 
of the Western and Central Pacific. Thus, based on the best available 
information, current levels of bigeye thresher mortality in commercial 
fisheries are not likely contributing to overutilization of the species 
throughout the entirety of the Western and Central Pacific, such that 
the species has a high risk of extinction throughout its global range, 
now or in the foreseeable future.
    In the Northwest Atlantic, the bigeye thresher is a common bycatch 
species in the U.S. pelagic longline fishery, with relatively high 
post-capture mortality rates. As previously discussed (see the common 
thresher Overutilization section), fisheries data from the Northwest 
Atlantic show a significant historical decline in the thresher 
population (common and bigeye threshers combined), likely due to 
exploitation of the species. While these data are not species-specific, 
the bigeye thresher is thought to be the more common of the two 
species. For example, observer data from 1992-2005 recorded 627 bigeye 
threshers, representing 81 percent of the identified thresher catch (in 
contrast to only 148 common thresher sharks recorded over the same time 
period, representing 19 percent of the identified thresher catch). This 
does not include the 1,067 thresher sharks that were not identified to 
species level (Baum and Blanchard, 2010). Nonetheless, despite the 
historical decline of thresher sharks in the Northwest Atlantic, the 
ERA team conducted a species-specific analysis using observer data from 
1992-2013 and found no obvious change in the population trend over time 
for the bigeye thresher shark. This analysis indicates that the 
population in this region has likely stabilized since 1990. While we 
acknowledge that fishing pressure on thresher sharks began over two 
decades prior to the start of this

[[Page 19005]]

time series (i.e., estimated historical declines are not from virgin 
biomass and the stabilization of the bigeye thresher population is 
therefore at a diminished abundance), existing regulations in this 
portion of the species' range appear to be minimizing this threat (see 
Inadequacy of Existing Regulatory Mechanisms section below for more 
details). Therefore, the ERA team concluded, and we agree, that 
overutilization in this portion of the species' range is not likely 
significantly contributing to a high risk of extinction for the species 
throughout its global range, now or in the foreseeable future.
    As previously noted, fisheries data for thresher sharks in the 
Northeast Atlantic and Mediterranean are scarce and unreliable due to 
the mixing of both thresher species in the records. The bigeye thresher 
has been poorly documented in the Mediterranean and is considered 
scarce or rare (Amorim et al., 2009); most of the available information 
from this region is for the common thresher. In fact, the bigeye 
thresher is often referred to as ``False Thresher'' in this region as a 
result of a perceived low local value (Cavanagh and Gibson, 2007). 
Although available data on catch trends for this species are lacking in 
the region, an increasing number of new records in recent years from 
the eastern Mediterranean (sometimes multiple captures) demonstrate 
that this species is widely distributed to the east of Malta, occurring 
in the waters off Israel (Levantine basin), in the Aegean Sea off 
Turkey and southern Greece, and off southern Crete. Evidence from 
offshore pelagic fisheries in southern Sicily and Malta indicate that 
bigeye thresher is caught in unknown numbers each year, but routinely 
discarded at sea (Cavanagh and Gibson, 2007). However, due to the lack 
of information regarding bigeye thresher catch trends, it is difficult 
to determine the status of bigeye thresher in the Mediterranean, and 
whether the species' scarce abundance in this region is a result of 
population declines due to fishing pressure or its natural rarity, or 
both.
    In the South Atlantic, bigeye thresher sharks are caught as bycatch 
in various longline fisheries, including those of Brazil, Uruguay, 
Taiwan, Japan, Venezuela, and Portugal, where they have shown to have 
high bycatch-related mortality rates. However, as previously noted, 
there is little information on the catch rates or trends in abundance 
of thresher sharks in the South Atlantic, with some countries still 
failing to collect or report shark data. Based on observer data from 
1994-2000, bigeye thresher represented only 2.2 percent of the total 
shark catch in the Venezuelan pelagic longline fishery; however, 
without corresponding effort data, discernable temporal trends are 
unavailable. Similarly, low CPUE rates were observed in Uruguayan 
longline fisheries despite high fishing pressure from 2001 to 2005; 
however, with such a short time series, temporal trends were also not 
discernable from this fishery. The only fishery for which a temporal 
trend is available is from the prominent Brazilian Santos and Guaruja 
tuna longline fishery that operates in the Southwest Atlantic. 
Standardized CPUE of bigeye thresher from this fishery showed a slight 
decline from 1978 to 2006, with bigeye threshers disappearing from the 
catch altogether in 2006. However, a shift in the distribution of 
fishing effort also occurred in 2006, moving from the equatorial 
Atlantic between 7[deg] N. and 5[deg] S. to around 20[deg] S. Thus, the 
disappearance of bigeye threshers from Brazilian longline catch can 
likely be attributed to the shift of fishing effort into more temperate 
waters, where the species is less prevalent. Given the high fishing 
pressure in this portion of the range, with evidence of high bycatch-
related mortality and slight declines in CPUE, overutilization is 
potentially negatively affecting the species in this part of its range. 
However, with only a slight decline in CPUE over the past several 
decades, and a geographical shift in effort of the Brazilian longline 
fleet to more temperate latitudes, fishing pressure on bigeye thresher 
may be on a decline in this part of its range and is likely not 
contributing to overutilization of the species such that it places the 
species at a high risk of extinction throughout its global range, now 
or in the foreseeable future.
    Overall, according to an ERA conducted in 2008 by the ICCAT 
Standing Committee on Research and Statistics for shark and ray species 
typically taken in Atlantic pelagic longline fisheries, Atlantic bigeye 
thresher sharks were identified as one of the least productive and most 
vulnerable sharks of the species examined. In addition, other more 
recent ERAs also found that the bigeye thresher's combination of low 
productivity and high susceptibility to pelagic longline gear places 
the species at a high risk of overexploitation (Cort[eacute]s et al. 
2010; Cort[eacute]s et al., 2012). The bigeye thresher's vulnerability 
to Atlantic fisheries is further confirmed by Gallagher et al. (2014) 
who found bigeye thresher emerged as one of the most vulnerable to 
longline bycatch mortality, as a result of the species' combined low 
fecundity and productivity, moderate age of maturity ranking, and low 
mean survival rate when caught (around 48 percent). However, despite 
the species' vulnerability to pelagic longline fisheries in the 
Atlantic, there is no evidence to suggest that the Atlantic bigeye 
thresher population has declined so significantly such that the 
species' global persistence is presently in question.
    The bigeye thresher shark has been reported in the catches of 
several fisheries operating in the Indian Ocean. While there are no 
abundance trends for bigeye thresher in the Indian Ocean, the IOTC 
acknowledges, and the ERA team agreed, that bycatch rates and 
associated mortality of bigeye thresher shark are likely high in Indian 
Ocean longline fisheries. Landings data reported to the IOTC are 
reported for the thresher complex and not identified to species, thus 
it is difficult to interpret this information with respect to bigeye 
thresher. However, given the bigeye thresher's high hooking mortality 
rate, the intensive fishing pressure in this region may be contributing 
to the overutilization of the species in the Indian Ocean. We note that 
this threat may also be exacerbated by the species' relatively high 
vulnerability to fisheries due to its slow growth and low productivity. 
Thus, in the absence of any trend data, we concluded conservatively 
that overutilization in the form of bycatch-related fishing mortality 
is likely contributing to population declines and increasing this 
species' risk of extinction in the Indian Ocean in the foreseeable 
future, although there are significant uncertainties. However, it 
should also be noted that longline fishing effort in the Indian Ocean 
appears to be declining as well as shifting to more temperate waters 
(Ardill et al., 2011) where bigeye threshers are less prevalent, which 
could potentially reduce fishing pressure on the species. Overall, 
based on the best available information, the ERA team agreed that 
overutilization of bigeye thresher in the form of indirect and direct 
fishing pressure is likely occurring in the Indian Ocean, but also 
noted that overutilization of the species in one particular region does 
not necessarily equate to a high risk of extinction to the global 
population, now or in the foreseeable future.
    The ERA team did not identify recreational fisheries as a threat to 
the bigeye thresher shark throughout its range. Although common 
threshers comprise an important aspect of the recreational fishery in 
southern

[[Page 19006]]

California, it is not known whether bigeye threshers enter the 
California recreational fishery on any regular basis, but presumably 
only few are taken. Further, there are no records of bigeye threshers 
from the recreational fishery off Oregon or Washington (NMFS, 2007), 
and in fact, a strict prohibition on recreational fishing of all 
thresher species was implemented in Washington State in 2013. Farther 
west in Hawaii, there were no catch records of bigeye thresher in the 
Hawaii recreational survey from 2003-2014 (Pers. comm. with NMFS 
Fisheries Statistics Division, October 14, 2015). In the Northwest 
Atlantic, data are generally extremely sparse for this species in U.S. 
recreational fisheries. Since prohibition of this species was 
implemented in 1999, there has been no observed recreational harvest of 
this species, with the exception of years 2002 and 2006, in which 
expanded survey estimates (which are highly unreliable due to large 
associated variances) estimated that 65 and 42 bigeye thresher sharks 
were caught and harvested, respectively (NMFS 2012; 2014). In fact, in 
most years of recreational data, dating back to 1981 and combining 
information from the Large Pelagics Survey and general Marine 
Recreational Information Program survey, bigeye threshers are typically 
not observed, with only 5 years showing bigeye threshers either landed 
or released alive throughout the Northwest Atlantic and Gulf of Mexico 
(Pers. comm. from NMFS, Fisheries Statistics Division, October 14, 
2015). We could not find any additional information on bigeye thresher 
in recreational fisheries outside of the United States. Thus, based on 
the best available information, we conclude that recreational fisheries 
are not currently a threat to the bigeye thresher shark, such that it 
places the species at an increased risk of extinction throughout its 
global range.
    Finally, the ERA team assessed the threat of the shark trade to the 
global extinction risk of the bigeye thresher. As previously described, 
the thresher complex has been reported as comprising approximately 2.3 
percent of the shark fin trade; however, the proportion of bigeye 
thresher in the fin trade is unknown. As discussed previously in the 
common thresher assessment, based on genetic analyses of fins in 
markets of major shark fin exporting countries throughout the range of 
the species, including Taiwan, Indonesia, and UAE, bigeye thresher fins 
have commonly been identified as present. In fact, bigeye thresher fins 
comprised approximately 7 percent of fins in numerous markets across 
Indonesia, which is one of the largest shark catching nations in the 
world. However, overall, the ERA team concluded that thresher sharks as 
a whole represent a relatively small portion of the fin trade, and the 
situation regarding the fin trade may be improving, as evidenced by a 
decline in both price and demand for fins. In fact, landings of 
thresher sharks in particular have declined in both Hawaii and American 
Samoa, which has been attributed to regulations prohibiting shark 
finning in the United States. Additionally, and as previously noted, 
thresher sharks were not historically identified as ``preferred'' or 
``first choice'' species for fins, with some traders considering 
thresher fins to be of low quality and value (Rose, 1996; FAO, 2002; 
Clarke, pers. comm. 2015). Furthermore, recent studies suggest that due 
to a waning interest in fins, the shark fin market is declining, and a 
surge in the trade of shark meat has occurred in recent years (Dent and 
Clarke, 2015; Eriksson and Clarke, 2015). However, as previously 
discussed in the common thresher Overutilization for Commercial, 
Recreational, Scientific or Educational Purposes section, it is 
unlikely that this shift in the shark trade would create new markets or 
increased demand for thresher species. This is particularly true for 
the bigeye thresher because it is not as highly regarded for human 
consumption due to the lower quality of the meat (Vannuccini, 1999). 
Therefore, based on the best available information, the ERA team 
concluded, and we agree, that although the bigeye thresher shark is 
likely more prevalent in the shark fin trade relative to the common 
thresher, finning for the shark fin trade is not a threat contributing 
to the overutilization of the species to the point that it 
significantly increases the species' risk of extinction throughout its 
global range, now or in the foreseeable future.

Disease or Predation

    The ERA team did not identify disease or predation as potential 
threats to the bigeye thresher shark, as they did not find evidence to 
suggest that either is presently contributing significantly to the 
species' risk of extinction. Like common thresher sharks, bigeye 
thresher sharks likely carry a range of parasites, including external 
copepods and cestodes. As previously described, nine species of 
copepods, genus Nemesis, parasitize thresher sharks. These parasites 
attach themselves to gill filaments, and can cause tissue damage which 
can then impair respiration in the segments of the gills (Benz and 
Adamson, 1999). The known parasite fauna of the bigeye thresher and 
associated references are reviewed in Gruber and Compagno (1981) and 
detailed in the status review report (see Young et al., 2015); however, 
the magnitude of impact these parasites may have on the health of 
bigeye thresher shark is unknown, but likely minimal.
    Predation is also not thought to be a factor influencing bigeye 
thresher numbers, as the bigeye thresher is a large shark with limited 
numbers of predators during all life stages. While they may be preyed 
upon by mako sharks, white sharks, killer whales, and even large sea 
lions, there is no information to suggest that this level of 
opportunistic predation is affecting bigeye thresher populations. 
Therefore, based on the best available information, the ERA team 
concluded, and we agree, that neither disease nor predation is 
currently placing the species in danger of extinction throughout its 
global range, now or in the foreseeable future.

Inadequacy of Existing Regulatory Mechanisms

    The ERA team evaluated existing regulatory mechanisms to determine 
whether they may be inadequate to address threats to the bigeye 
thresher shark. Existing regulatory mechanisms may include Federal, 
state, and international regulations for commercial and recreational 
fisheries, as well as the international shark trade. Below is a brief 
description and evaluation of current and relevant domestic and 
international management measures that may affect the bigeye thresher 
shark. Since many of the broader regulatory mechanisms that may affect 
sharks in general were already discussed in the common thresher 
Inadequacy of Existing Regulatory Mechanisms section of this finding 
(e.g., U.S. regulations to conserve and manage shark species), the 
following will only cover the existing regulatory mechanisms specific 
to bigeye thresher, and in the regions where overutilization was deemed 
a potential threat to the species or in regions that were not addressed 
in the common thresher assessment (e.g., Caribbean). More information 
on these domestic and international management measures can be found in 
the status review report (Young et al., 2015) and other recent status 
reviews of other shark species (Miller et al., 2013; 2014).
    In the Northwest Atlantic, in addition to all of the previously 
described regulatory mechanisms regarding U.S. HMS fisheries for 
pelagic sharks, the U.S. FMP for Atlantic Tunas, Swordfish,

[[Page 19007]]

and Sharks implemented a specific measure in 1999 that effectively 
prohibited retention of bigeye thresher sharks, among several other 
pelagic shark species. The designation of bigeye thresher shark as a 
prohibited species was a precautionary measure to ensure that directed 
fisheries and/or markets did not develop. However, we recognize that 
bigeye threshers are still incidentally caught as bycatch on pelagic 
longlines and in gillnets in the Northwest Atlantic, and have 
relatively high bycatch-related mortality rates. For example, since the 
prohibition on bigeye threshers came into effect in 2000, approximately 
1,493 lb, dressed weight (677 kg) of bigeye thresher were landed in the 
Atlantic (NMFS, 2012; 2014) despite its prohibited status, although 
this equates to few sharks based on average weight. Further, the United 
States reported that bigeye thresher represented one of the largest 
amounts of dead discards in the Atlantic commercial fleet, reporting a 
total of 46 mt in 2009 and 27 mt in 2010 (NOAA, 2010 and 2011 Reports 
to ICCAT). However, in the most recent available report to ICCAT, 
bigeye thresher sharks were not listed among the largest amounts of 
dead discards. In fact, in 2012 and 2013, NMFS reported prohibited 
shark interactions of bigeye thresher to ICCAT, with a total of 38 and 
33 mt of bigeye threshers caught as bycatch, respectively, with more 
than half released alive (NMFS, 2013; 2014). Therefore, these bycatch 
numbers are down significantly from earlier reports of hundreds of 
thresher sharks caught as bycatch in the late 1980s and early 1990s 
(NMFS 2009 Report to ICCAT), which was prior to management regulations. 
Although we recognize that bigeye threshers are still caught and 
discarded in these fisheries, the ERA team determined that current 
levels may be sustainable, as evidenced by a continuing stable CPUE 
trend based on observer data, which accounts for bycatch-related 
mortality. In fact, as previously discussed, recent standardized CPUE 
data for the bigeye thresher shark suggest the population has 
stabilized since the 1990s, which corresponds to the advent of pelagic 
shark species management as well as species-specific management 
measures for the bigeye thresher.
    In addition, the HMS Management Division recently published an 
amendment to the Consolidated HMS FMP that specifically addresses 
Atlantic HMS fishery management measures in the U.S. Caribbean 
territories (77 FR 59842; Oct. 1, 2012). Due to substantial differences 
between some segments of the U.S. Caribbean HMS fisheries and the HMS 
fisheries that occur off the mainland of the United States (including 
permit possession, vessel size, availability of processing and cold 
storage facilities, trip lengths, profit margins, and local consumption 
of catches), the HMS Management Division implemented measures to better 
manage the traditional small-scale commercial HMS fishing fleet in the 
U.S. Caribbean Region. Among other things, this rule created an HMS 
Commercial Caribbean Small Boat (CCSB) permit, which: Allows fishing 
for and sales of big-eye, albacore, yellowfin, and skipjack tunas, 
Atlantic swordfish, and Atlantic sharks within local U.S. Caribbean 
market; collects HMS landings data through cooperation with NMFS and 
existing territorial government programs; authorizes specific gears; is 
restricted to vessels less than or equal to 45 feet (13.7 m) length 
overall; and may not be held in combination with any other Atlantic HMS 
vessel permits. However, at this time, fishermen who hold the CCSB 
permit are prohibited from retaining Atlantic sharks, and are 
restricted to fishing with only rod and reel, handline, and bandit gear 
under the permit. Both the CCSB and Atlantic HMS regulations will help 
protect bigeye thresher sharks while in the Northwest Atlantic Ocean, 
Gulf of Mexico, and Caribbean Sea.
    In addition to U.S. regulatory mechanisms, there are also 
international regulatory mechanisms specific to bigeye thresher in the 
Atlantic Ocean. In 2009, ICCAT adopted Recommendation 09-07, which 
prohibits the retention of bigeye threshers caught in association with 
ICCAT-managed fisheries. Each Contracting Party to ICCAT is responsible 
for implementing this recommendation, and currently there are 
approximately 47 contracting parties (including the United States, the 
EU, Brazil, Venezuela, Senegal, Mauritania, and many other Central 
American and West African countries). The ICCAT Recommendation 09-07 
includes a special exception for a Mexican small-scale coastal fishery 
with a catch of less than 110 fish. Based on the nominal catch data 
from ICCAT, it appears that catches of bigeye thresher sharks by ICCAT 
vessels have been on a decline since the implementation of this 
measure. Prior to Recommendation 09-07, average reported bigeye 
thresher catch was approximately 82 mt per year (range: 0 to 185 mt; 
1993-2009). In 2014, only fleets operating under U.S., Brazil, and 
Trinidad and Tobago flags reported catches of bigeye thresher sharks 
(total = 25 mt). These declining numbers reported by ICCAT vessels may 
be a reflection of the efficacy of Recommendation 09-07 for reducing 
the number of landed bigeye thresher sharks, as well as the previously 
described regulation implemented by Spain, a main thresher catching 
country in the Atlantic, that prohibits the landing and sale of any 
thresher species. Although these retention bans do not address bycatch-
related mortality, they likely provide some benefit to the bigeye 
thresher shark, particularly given that the species was historically 
retained as bycatch in ICCAT fisheries. Therefore, although the bigeye 
thresher has relatively high vulnerability (susceptibility and 
productivity) to ICCAT fisheries, regulations prohibiting the retention 
of bigeye thresher sharks help to minimize the threat of 
overutilization of this species within the Atlantic Ocean.
    In the Western and Central Pacific, the Western and Central Pacific 
Fisheries Commission (WCPFC) is the main regulatory body for the 
management of sharks. Unlike ICCAT and IOTC, the WCPFC has no 
regulatory measures specific for the conservation of thresher sharks. 
However, thresher sharks are designated as ``key shark species'' in the 
WCPFC area, which means they are nominated for the purposes of either 
data provision and/or assessment. Thresher sharks were nominated for 
assessment and are thus included in the WCPFC's Shark Research Plan. 
Additionally, the WCPFC has implemented a number of conservation 
management measures (CMMs), that, although have variable implementation 
rates by the WCPFC members (CCMs), likely confer some conservation 
benefits for bigeye thresher, including reporting requirements and a 
five percent fin to carcass ratio (CMM 2010-07). As previously 
discussed in the common thresher Inadequacy of Existing Regulatory 
Mechanisms section of this finding, we note a number of issues 
regarding the five percent fin to carcass ratio. However, in a recent 
study of longline fisheries (Rice et al. 2015), the percentage of key 
shark species that were finned reduced from 2010 to 2013, with the last 
year of the study showing an increase in finning and a decrease in the 
number of sharks retained. The decrease in finning from 2010 to 2013 
corresponded with an increase in retention, which would be the 
expectation if fishers were beginning to retain the carcass to adhere 
to CMM 2010-07 (the five percent fin to carcass rule) (Rice et al. 
2015). However, this could also be due to the growing demand for shark 
meat and a waning

[[Page 19008]]

interest in shark fins, as discussed earlier (see Dent and Clarke 
(2015) and Eriksson and Clarke (2015) for more details). Despite the 
increase in finning of key shark species in the last year of the Rice 
et al. (2015) study, the fate of thresher sharks in longline gear shows 
a declining trend in the number of threshers finned since 2007 in the 
Western and Central Pacific Ocean. This may be indicative of the 
efficacy of conservation measures in this region, although this remains 
uncertain. More recently, however, the WCPFC also adopted CMM 2014-05 
(effective July 2015) that requires each national fleet to ban the use 
of wire trace as branch lines or leaders and shark lines, which has 
been shown to significantly reduce shark bycatch in the first place.
    As previously noted, inadequate regulatory mechanisms to control 
for overutilization of thresher species were noted as problematic 
throughout the Indian Ocean. The IOTC is the only RFMO that has 
specific regulations for all three thresher species. In 2010, the IOTC 
implemented Resolution 12/09 on the conservation of thresher species, 
which prohibits retaining on board, transhipping, landing, storing, 
selling or offering for sale any part or whole carcass of thresher 
sharks of all the species of the family Alopiidae. However, despite the 
prohibition on landings of Alopias spp., reported landings of 
unidentified thresher species have continued through 2012, indicating 
that regulations in the Indian Ocean may not be fully implemented or 
enforced. In fact, thresher sharks were marketed in local markets up 
until at least early 2011 despite IOTC Resolution 12/09. However, the 
IOTC reported 0 mt of bigeye thresher in their most recent catch 
estimates for 2013 and 2014 (IOTC, 2015), which may indicate that CPCs 
are beginning to adhere to the retention ban. Nevertheless, the IOTC 
itself acknowledges that its own retention ban for thresher sharks may 
not be adequate for the bigeye thresher shark due to its high bycatch-
related mortality rates, low productivity, as well as high rates of 
illegal fishing and the reluctance of CPCs to adequately report 
discards in the Indian Ocean. However, as of 2015, the IOTC recommended 
that the retention ban remain in place, as it likely confers some 
conservation benefit (albeit limited) to bigeye thresher. Thus, due to 
the high fishing pressure in this region, combined with likely 
ineffective implementation and enforcement of regulations, the IOTC's 
main regulation to conserve thresher species may be ineffective (IOTC, 
2014). Like the WCPFC, the IOTC also prohibits fins onboard that weigh 
more than five percent of the weight of sharks to curb the practice of 
shark finning. As previously noted, these regulations do not prohibit 
the fishing of sharks and there are a number of issues related to the 
five percent fin to carcass ratio. However, unlike the WCPFC, we have 
no information regarding the trend of finning of thresher sharks to 
determine whether these regulations have had any effect on the fate of 
thresher sharks in Indian Ocean longline fisheries. Thus, the ERA team 
concluded, and we agree, that regulatory mechanisms are likely 
inadequate to control for potential overutilization of bigeye thresher 
shark in the Indian Ocean. However, as previously noted, due to a lack 
of abundance estimates and catch records for bigeye thresher in this 
region, the magnitude of population decline in the Indian Ocean could 
not be determined. Further, the ERA team also concluded that 
overutilization and inadequate existing regulatory mechanisms in one 
portion of the species' range does not automatically place the species 
at a high risk of extinction globally, now or in the foreseeable 
future.
    Although inadequate regulations to control for overutilization via 
the shark fin trade were an initial concern to the ERA team, as the 
bigeye thresher was identified to species in several genetic tests of 
fins in various portions of its range, and seemed to comprise a large 
portion of fins in markets across Indonesia (one of the largest shark 
catching countries in the world), we note that overall, thresher fins 
do not make up a large portion of the shark fin trade (~2.3 percent) 
relative to other species, such as blue, mako, and hammerhead sharks. 
Additionally, the reported 2.3 percent is for the thresher complex and 
likely includes a large number of pelagic thresher sharks, given their 
range and distribution overlaps with bigeye thresher, they comprise a 
significant component of thresher fins identified in the aforementioned 
genetic studies, and they comprise the majority of thresher catches in 
some areas. As noted previously, thresher shark fins are also not 
considered highly valued or ``first choice'' among some traders. 
Finally, and as previously discussed, the situation regarding the fin 
trade appears to be improving in some areas (refer back to common 
thresher--Overutilization for Commercial, Recreational, Scientific, and 
Educational Purposes section), with an overall decline in the global 
fin trade occurring in recent years. For example, a decrease in 
landings of thresher sharks was reported in Hawaii and American Samoa, 
which has been attributed to regulations that prohibit shark finning in 
the United States, and may also be indicative of the efficacy of these 
regulations. Further, several RFMOs, countries and local governments 
have enacted both shark finning and species-specific retention bans 
that likely confer some benefit to bigeye thresher sharks by reducing 
the number of sharks retained solely for their fins. We note these 
retention and finning bans may not be effective in some areas, such as 
the Indian Ocean; however, they may be more effective in other portions 
of the species' range. For example, the fate of thresher sharks as 
``finned'' in the Western and Central Pacific has been on a decline 
since 2007. Additionally, since the implementation of ICCAT 
Recommendation 09-07 on the conservation of thresher sharks, as well as 
Spain's national retention ban for all thresher species, reported 
landings of bigeye thresher to ICCAT have significantly declined. This 
indicates that at least in some portions of the species' range, 
regulations may be adequate in their intended purpose. Overall, 
although bigeye thresher shark fins are somewhat prevalent in the shark 
fin trade, the effect of the shark fin trade (from both legal and 
illegal harvest) on their extinction risk was not viewed as a 
significant threat. Additionally, as both the supply and demand for 
shark fins continue to decrease (as demonstrated by the increase in 
finning regulations and decrease in shark fin consumption and price, 
respectively), so should the threat of finning and illegal harvest. 
While an increase in the demand for shark meat is apparent in recent 
years, we have no evidence to suggest that the bigeye thresher will 
experience new or increased demand as a result of this shift in the 
market (refer back to the common thresher Overutilization for 
Commercial, Recreational, Scientific, or Educational Purposes section 
for more details), particularly since bigeye thresher meat is not 
highly regarded as food due to its lower quality.
    Based on the above review of regulatory measures (in addition to 
the regulations described in Young et al., 2015), the ERA team 
concluded that these existing regulations are adequate and do not 
contribute to the species' extinction risk throughout its range, now or 
in the foreseeable future. The team noted that some areas of the 
species' range do have adequate measures in place to prevent 
overutilization, such as in the Northwest Atlantic where U.S. fishery

[[Page 19009]]

management measures are helping to monitor the catch of bigeye 
threshers, preventing any further population declines. These U.S. 
conservation and management measures (as previously summarized) are 
viewed as adequate in decreasing the extinction risk to the bigeye 
thresher shark in this portion of its range by minimizing demographic 
risks (preventing further abundance declines) and the threat of 
overutilization (strictly prohibiting bigeye threshers in both 
commercial and recreational fisheries) currently and in the foreseeable 
future. Likewise, U.S. management regulations for the Hawaii-based 
pelagic longline fishery are also likely adequate in reducing impacts 
to the bigeye thresher, as evidenced by a stable and possibly 
increasing abundance trend of the species in this region of the Central 
Pacific. Although regulations specific to bigeye thresher sharks are 
lacking in other parts of its range, it is unclear whether 
overutilization presents a significant threat to the species in these 
regions (see Overutilization for Commercial, Recreational, Scientific 
or Educational Purposes section discussed earlier in this notice), and 
thus it is difficult to determine whether the inadequacy of current 
regulatory measures is placing the species at an increased risk of 
extinction throughout its global range. Overall, implementation and 
enforcement of regulatory mechanisms is variable throughout the range 
of the bigeye thresher. We recognize the mere existence of regulatory 
mechanisms does not necessarily equate to their effectiveness in 
achieving their intended purpose. Issues related to community 
awareness, compliance, enforcement, regional priorities, and complex 
political climates within many countries in which thresher sharks occur 
can limit the effectiveness of well-intended statutes and legislation. 
However, based on the best available information, we find that although 
improvements are needed in the monitoring and reporting of fishery 
interactions of this species, the threat of inadequate existing 
regulatory mechanisms is not likely causing the species to have a high 
risk of extinction throughout its global range, now or in the 
foreseeable future.

Other Natural or Manmade Threats

    As previously described, the ERA team assessed the effects of 
climate change as a potential threat to bigeye thresher sharks; 
however, since most of the studied impacts from climate change are 
habitat-focused, the threat of climate change is addressed in the 
Present or Threatened Destruction, Modification, or Curtailment of its 
Habitat or Range section of this finding. Other threats that fall under 
Factor E (ESA section 4(a)(1)(E)), including pollution and potential 
threats to important prey species are addressed in the status review 
report (Young et al., 2015), but were not identified as threats that 
rose to the level of increasing the species' risk of extinction.

Overall Risk Summary

    Guided by the results from the demographic risk analysis and 
threats assessment, the ERA team members used their informed 
professional judgment to make an overall extinction risk determination 
for the bigeye thresher shark now and in the foreseeable future. The 
ERA team concluded that the bigeye thresher shark is currently at a low 
risk of extinction. However, due to a lack of abundance trends and 
catch data for a large portion of the species' range, the ERA team 
expressed uncertainty by spreading their likelihood points across all 
categories. Likelihood points attributed to the overall level of 
extinction risk categories were as follows: Low Risk (34.5/70), 
Moderate Risk (30.5/70), High Risk (5/70). The ERA team reiterated that 
across the species' range, regional abundance trends are highly 
variable, with no clear trend for the global population. There is also 
no evidence to suggest depensatory processes are currently at work. The 
species is found globally, throughout its historical range, appears to 
be well-adapted, and is not limited by habitat. Although the global 
abundance of bigeye thresher shark is highly uncertain, none of the 
available regional studies that reported recent standardized CPUEs 
(Northwest Atlantic, South Atlantic, Hawaii, Western and Central 
Pacific), and give some insight into the species' current abundance, 
show a significant or continuing decline such that demographic risks 
are significantly contributing to the species' risk of extinction. 
Based on most recent fisheries data, the ERA team concluded that at 
least some populations of bigeye thresher are not overutilized and 
current fishing pressure and associated mortality on these populations 
may be sustainable. We recognize that the bigeye thresher's tropical 
distribution may increase the species' exposure to many high seas 
industrial fisheries operations throughout its range, particularly 
where fishing pressure is likely highest within the Indo-Pacific. This 
is evidenced by the fact that the species is commonly observed or 
caught throughout this portion of its range (including where 
regulations may be inadequate--which may increase the impact of this 
potential threat on its contribution to the extinction risk of the 
species) and is present in several genetic tests of shark fins 
throughout its range, indicating that the species is utilized to some 
degree in the shark fin trade. We recognize that the bigeye thresher 
may be experiencing some degree of population decline in the Western 
and Central Pacific and Indian Oceans; however, the magnitude of 
decline in the Western and Central Pacific was considered to be 
``slight'' in recent years, with a conservative assumption that the 
available CPUE and landings data (which are reported for the thresher 
complex (all three Alopias spp.)) are indeed reflective of trends in 
bigeye thresher. Additionally, the potential decline in the Indian 
Ocean is considered to be highly uncertain given that fisheries data 
(including nominal and standardized CPUE trends) are largely lacking 
from this portion of the species' range, with landings data also pooled 
for all thresher species. However, the ERA team agreed that the 
potential declines of bigeye thresher in these portions of its range 
are not likely to be so severe such that they place the species at a 
high risk of extinction throughout its global range, now or in the 
foreseeable future.
    The available information indicates that most of the observed 
declines occurred historically, before any significant management 
regulations were in place. Since then, current regulatory measures in 
some parts of the bigeye thresher range are reducing the threat of 
overutilization, and likely preventing further abundance declines in 
these portions in the foreseeable future. Therefore, the ERA team 
concluded that at least some populations are not suffering from 
overutilization and are well managed, thus decreasing the likelihood of 
extinction of the global population. The ERA team acknowledged that 
given the species' low productivity and high bycatch-related mortality 
rates, it is generally more vulnerable to unsustainable levels of 
exploitation. However, given the best available information, the ERA 
team concluded that over the next 50 years, it is unlikely that the 
bigeye thresher shark has a high risk of extinction throughout its 
global range, now or in the foreseeable future, due to current trends 
in its abundance, productivity, spatial structure, or diversity or 
influenced by depensatory processes, effects of environmental 
stochasticity, or catastrophic events.

Significant Portion of Its Range

    If we find that the bigeye thresher is not in danger of extinction 
now or in the

[[Page 19010]]

foreseeable future throughout all of its range, we must go on to 
evaluate whether the species is in danger of extinction, or likely to 
become so in the foreseeable future, in a ``significant portion of its 
range'' (79 FR 37578; July 1, 2014). Please refer back to the common 
thresher Significant Portion of Its Range section of this finding for 
detailed information regarding the SPR Policy and process.
    Applying the SPR policy to the bigeye thresher shark, we first 
evaluated whether there is substantial information indicating that the 
species may be threatened or endangered in any portion of its range. 
After a review of the best available information, the ERA team 
concluded, and we agree, that the Indian Ocean likely has more 
concentrated threats than other portions of the bigeye thresher's range 
due to the intensive fishing pressure in this region, combined with the 
species' high rates of bycatch-related mortality and low productivity. 
However, with virtually no information regarding abundance trends or 
catch data of bigeye thresher from this region, we cannot conclude that 
the species is in danger of extinction or likely to become so in the 
foreseeable future in this portion of its range. Even if the bigeye 
thresher was in danger of extinction in the Indian Ocean (or likely to 
become so in the foreseeable future), the ERA team concluded that the 
loss of the Indian Ocean population of bigeye thresher would not result 
in the remainder of the species being endangered or threatened. In 
particular, we did not find substantial evidence to indicate that the 
loss of this portion would result in a level of abundance for the 
remainder of the species to be so low or variable, that it would cause 
the species to be at a moderate or high risk of extinction due to 
environmental variation, anthropogenic perturbations, or depensatory 
processes. Bigeye thresher sharks are highly mobile, globally 
distributed, and have no known barriers to migration. Although there is 
preliminary evidence of possible genetic partitioning between ocean 
basins, this was based on one study with a limited sample size (see 
Trejo, 2005_ENREF_224). Thus, there is no substantial evidence to 
suggest that the loss of the Indian Ocean portion of its range would 
severely fragment and isolate the species to the point where the 
remaining populations would be at risk of extinction from demographic 
processes. In fact, we found no information that would suggest that the 
remaining populations could not repopulate the lost portion, and, if 
for some reason the species could not repopulate the lost portion, it 
would still not constitute a significant risk of extinction to the 
remaining populations. We did not find substantial evidence to indicate 
that the loss of genetic diversity from one portion (such as loss of 
the Indian Ocean population) would result in the remaining population 
lacking enough genetic diversity to allow for adaptations to changing 
environmental conditions. Additionally, areas exhibiting source-sink 
dynamics, which could affect the survival of the species, were not 
evident in any part of the bigeye thresher shark range. There is also 
no evidence of a portion that encompasses aspects that are important to 
specific life history events but another portion that does not, where 
loss of the former portion would severely impact the growth, 
reproduction, or survival of the entire species. There is also limited 
information regarding nursery grounds or other important habitats 
utilized by the species that could be considered limiting factors for 
the species' survival. In fact, we found evidence that there are likely 
reproductive grounds and nursery areas in all three major ocean basins. 
In other words, the viability of the species does not appear to depend 
on the productivity of the population or the environmental 
characteristics in any one portion. Overall, we did not find any 
evidence to suggest that any specific portion of the species' range had 
increased importance over any other with respect to the species' 
survival. As such, we did not identify any portions of the bigeye 
thresher range, including the Indian Ocean, that meet both criteria 
under the SPR Policy (i.e., the portion is biologically significant and 
the species may be in danger of extinction in that portion, or likely 
to become so within the foreseeable).

Final Determination

    Section 4(b)(1) of the ESA requires that NMFS make listing 
determinations based solely on the best scientific and commercial data 
available after conducting a review of the status of the species and 
taking into account those efforts, if any, being made by any state or 
foreign nation, or political subdivisions thereof, to protect and 
conserve the species. We have independently reviewed the best available 
scientific and commercial information, including the petition, public 
comments submitted on the 90-day finding (80 FR 48061; August 11, 
2015), the status review report (Young et al., 2015), and other 
published and unpublished information, and have consulted with species 
experts and individuals familiar with bigeye thresher sharks. We 
considered each of the ESA Section 4(a)(1) factors to determine whether 
it presented an extinction risk to the species on its own. We also 
considered the combination of those factors to determine whether they 
collectively contributed to the extinction of the species. As 
previously explained, no portion of the species' range is considered 
significant, so we concluded that the species is not threatened or 
endangered in a significant portion of its range. Therefore, our 
determination set forth below is based on a synthesis and integration 
of the foregoing information, factors and considerations, and their 
effects on the status of the species throughout its entire range.
    We conclude that the bigeye thresher shark is not presently in 
danger of extinction, nor is it likely to become so in the foreseeable 
future, throughout all of its range. We summarize the factors 
supporting this conclusion as follows: (1) The species is broadly 
distributed over a large geographic range, with no barrier to 
dispersal; (2) its current range is indistinguishable from its 
historical range and there is no evidence of habitat loss or 
destruction; (3) while the species possesses life history 
characteristics that increase its vulnerability to harvest, and has 
been found to be more susceptible to pelagic longline fisheries 
compared to other shark species (based on results from Ecological Risk 
Assessments), the species is still regularly encountered in fisheries 
and appears sustainable in some portions of its range despite decades 
of fishing pressure; (4) the best available information indicates that 
abundance is variable across the species' range, with reports of 
localized population declines but also evidence of stable and/or 
increasing abundance estimates; (5) based on the ERA team's assessment, 
while the current population size has likely declined from historical 
numbers, it is sufficient to maintain population viability into the 
foreseeable future; (6) there is no evidence that disease or predation 
is contributing to an increased risk of extinction of the species; (7) 
existing regulatory mechanisms to address the most important threats to 
the species (harvest) are not inadequate throughout its range, such 
that they contribute significantly to the species' risk of extinction 
globally; (8) there is no evidence that other natural or manmade 
factors are contributing to an increased risk of extinction of the 
species; and (9) while the global population has likely declined from 
historical numbers, there is no evidence that the species is

[[Page 19011]]

currently suffering from depensatory processes (such as reduced 
likelihood of finding a mate or mate choice or diminished fertilization 
and recruitment success) or is at risk of extinction due to 
environmental variation or anthropogenic perturbations.
    Based on these findings, we conclude that the bigeye thresher shark 
is not currently in danger of extinction throughout all or a 
significant portion of its range, nor is it likely to become so within 
the foreseeable future. Accordingly, the bigeye thresher shark does not 
meet the definition of a threatened or endangered species, and thus, 
the bigeye thresher shark does not warrant listing as threatened or 
endangered at this time.

References

    A complete list of all references cited herein is available upon 
request (see FOR FURTHER INFORMATION CONTACT).

Authority

    The authority for this action is the Endangered Species Act of 
1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: March 28, 2016.
Samuel D. Rauch III,
Deputy Assistant Administrator for Regulatory Programs, National Marine 
Fisheries Service.
[FR Doc. 2016-07440 Filed 3-31-16; 8:45 am]
 BILLING CODE 3510-22-P