[Federal Register Volume 82, Number 36 (Friday, February 24, 2017)]
[Notices]
[Pages 11540-11558]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-03644]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[Docket No. 150901797-7177-02]
RIN 0648-XE163


Endangered and Threatened Wildlife and Plants; Notice of 12-Month 
Finding on a Petition To List Thorny Skate 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; 12-month finding and availability of status review 
document.

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SUMMARY: We, NMFS, have completed a comprehensive status review under 
the Endangered Species Act (ESA) for thorny skate (Amblyraja radiata) 
in response to a petition to list this species. Based on the best 
scientific and commercial information available, including the status 
review report, and taking into account ongoing efforts to protect this 
species, we have determined that the listing of a Northwest Atlantic 
(NWA) distinct population segment (DPS) or a U.S. DPS is not warranted 
at this time. While the petition only sought the listing of one of two 
alternative DPSs, we exercised our discretion to consider whether the 
listing of the species at the taxonomic level is warranted. We conclude 
that thorny skate is not currently in danger of extinction throughout 
all or a significant portion of its range or likely to become so in the 
foreseeable future.

DATES: This finding was made on February 24, 2017.

ADDRESSES: The status review document for thorny skate is available 
electronically at: www.nmfs.noaa.gov/pr/species/notwarranted.htm. You 
may also obtain a copy by submitting a request to the Protected 
Resources Division, NMFS GARFO, 55 Great Republic Drive, Gloucester, MA 
01930, Attention: Thorny Skate 12-month Finding.

FOR FURTHER INFORMATION CONTACT: Kim Damon-Randall, NMFS Greater 
Atlantic Regional Fisheries Office, 978-282-8485; or Marta Nammack, 
NMFS Office of Protected Resources, 301-427-8469.

SUPPLEMENTARY INFORMATION:

Background

    We received a petition, dated May 28, 2015, from Animal Welfare 
Institute (AWI) and Defenders of Wildlife (DW) requesting that we list 
a ``Northwest Atlantic DPS'' of thorny skate as threatened or 
endangered under the ESA, or, as an alternative, a ``U.S. DPS'' as 
threatened or endangered. The petition also requests we designate 
critical habitat for thorny skate. In response to this petition, we 
published a ``positive'' 90-finding on October 26, 2015 (80 FR 65175), 
in which we concluded that the petition presented substantial 
scientific and commercial information indicating that listing under the 
ESA may be warranted, and a review of the status of the species was 
initiated.
    We then performed a detailed review and determined that the best 
available scientific and commercial information does not support a 
listing. The resulting status review report included an in-depth review 
of the available scientific literature, an analysis of the five ESA 
section 4(a)(1) factors (16 U.S.C. 1533(a)(1)(A)-(E)), and an 
assessment of extinction risk. The status review report was 
independently peer reviewed by external experts. This listing 
determination is based on the status

[[Page 11541]]

review report, along with other published and unpublished information.

Listing Species Under the ESA

    We are responsible for determining whether the thorny skate is 
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). Under the 
joint DPS policy, we consider the following 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 species or subspecies to 
which it belongs.
    Section 3 of the ESA further defines an endangered species as ``any 
species which is in danger of extinction throughout all or a 
significant portion of its range'' and a threatened species as one 
``which is likely to become an endangered species within the 
foreseeable future throughout all or a significant portion of its 
range.'' Thus, we interpret an ``endangered species'' to be one that is 
presently in danger of extinction. A ``threatened species,'' on the 
other hand, is not presently in danger of extinction, but is likely to 
become so in the foreseeable future (that is, at a later time). In 
other words, the primary statutory difference between a threatened and 
endangered species is the timing of when a species may be in danger of 
extinction, either presently (endangered) or in the foreseeable future 
(threatened). Section 4(a)(1) of the ESA 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. 
(16 U.S.C. 1533(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 domestic 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

    The status review report for thorny skate is composed of two 
components: (1) A scientific literature review and analysis of the five 
ESA section 4(a)(1) factors and (2) an assessment of the extinction 
risk. A biologist in NMFS' Greater Atlantic Region, working in 
cooperation with NMFS Northeast Fisheries Science Center (NEFSC), 
completed the first component, undertaking a scientific review of the 
life history and ecology, distribution and abundance, and an analysis 
of the ESA section 4(a)(1) factors. The Extinction Risk Assessment 
(ERA) was compiled by a biologist in NMFS' Greater Atlantic Region. The 
ERA was informed by invited workshop participants who based their 
individual expert opinions on the information contained in the 
scientific literature review. The workshop participants were comprised 
of a fisheries management specialist from NMFS' Highly Migratory 
Species Management Division, two research fishery biologists from NMFS' 
Northeast Fisheries Science Center, an elasmobranch expert from Sharks 
International, a fisheries manager from the New England Fishery 
Management Council, and a research director from the New England 
Aquarium. The workshop participants had expertise in elasmobranch 
biology and ecology, population dynamics, fisheries management, climate 
change and/or stock assessment science. The workshop participants 
reviewed the information from the scientific literature review. The 
status review report for thorny skate (NMFS 2017) compiles the best 
available information on the status of the 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, focusing primarily on threats related to the 
five statutory factors set forth above. We prepared this report to 
summarize the workshop participants' professional judgments of the 
extinction risk facing thorny skate. The workshop participants made no 
recommendations as to the listing status of the species, nor does the 
status review report. The status review report is available 
electronically at the Web site listed in ADDRESSES.
    The status review report underwent 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 government, academic, and scientific communities, with 
expertise in elasmobranch biology, conservation and management, and 
specific knowledge of thorny skates. The peer reviewers were asked to 
evaluate the adequacy, quality, and completeness of the data considered 
and whether uncertainties in these data were identified and 
characterized in the status review report, as well as to evaluate the 
findings made in the ``Assessment of Extinction Risk'' section of the 
report. They were also asked to specifically identify any information 
missing or lacking justification, or whether information was applied 
incorrectly in reaching conclusions. We addressed all peer reviewer 
comments prior to finalizing the status review report. Comments 
received are posted online at www.cio.noaa.gov/services_programs/prplans/ID365.html.
    We subsequently reviewed the status review report, the cited 
references, and the peer review comments, and we concluded that the 
status review report, upon which this listing determination is based, 
provides the best available scientific and commercial information on 
thorny skate. Much of the information discussed below on thorny skate 
biology, genetic diversity, 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 and 
Significant Portion of its Range (SPR) policies in making the listing 
determination.

Distribution and Habitat Use

    The thorny skate belongs to the family Rajidae, genus Amblyraja, 
and species radiata. The thorny skate is a widely distributed boreal 
species, spanning both sides of the Atlantic. In the western North 
Atlantic, it ranges from western

[[Page 11542]]

Greenland to South Carolina. In the eastern North Atlantic, it ranges 
from the Barents Sea southward to the southwestern coasts of Ireland 
and England, including Iceland (Bigelow and Schroeder, 1953). Found 
over a wide variety of substrates including sand, broken shell, gravel, 
pebbles and soft mud, the thorny skate ranges over depths from 18 to 
1400 m (COSEWIC 2012).
    Despite its generalist nature, some habitat preferences exist. 
There is some evidence that the species prefers complex hard bottom 
habitat instead of sand or mud. Scott (1982) reported that catch rates 
of thorny skate were highest on coarser grained sediment, and catch 
rates diminished as grain size decreased on the Scotian Shelf. Also, 
more skates are caught by longlines in bottom areas that are considered 
categorized as rough versus those considered smooth (Sosebee et al., in 
prep).
    Generally, thorny skate appear to prefer deeper waters within their 
range, although the specific depth varies by location and may be 
impacted by other factors including temperature. Survey data from the 
inshore waters in the Gulf of Maine stratified by depth indicate catch 
by trawl survey gear increases sharply in depths greater than 40 meters 
(m), and peaks at around 95 m. Most individuals are caught between 70 m 
and the upper depth limit for the survey, 120 m (Sosebee et al., in 
prep). Generally, within U.S. waters, they range from a depth of 141 to 
300 m in spring and 31 to 500 m in fall, with the majority of both 
spring and fall captures between 141 to 300 m (Packer et al., 2003). 
Previous studies found thorny skate most abundant between 111 m and 366 
m throughout the U.S. range (McEachran and Musick 1975). In Canadian 
waters from the Labrador Shelf to the Grand Banks, 88 percent of thorny 
skate are found between 30 and 350 m (COSEWIC 2012). In the Gulf of St. 
Lawrence, thorny skate have been found to be increasingly concentrated 
in depths below 100 m since the early 1990s, with the majority of fish 
greater than 33 centimeters (cm) in length found around 200 m (Swain 
and Benoit 2006). Fish smaller than 33 cm concentrate in shallower 
waters around 100 m in the Gulf of St. Lawrence. In Norway, thorny 
skate show a preference for even deeper waters, being more concentrated 
between 600 and 650 m (Williams et al., 2008). Within the Barents Sea, 
average catch is highest between 100 and 200 m but thorny skates are 
captured all the way to 800 m (Dolgov et al., 2005a). Together, this 
information demonstrates that thorny skate occur in a wide range of 
depths throughout their range, but are most likely to occur in deeper 
waters.
    Thorny skate have been caught at temperatures ranging from -1.4 to 
14 [deg]Celsius (C) (McEachran and Musick 1975); however, they have a 
more narrow thermal range than most sympatric species (Hogan et al., 
2013). In the U.S. waters of the inshore Gulf of Maine, surveys catch 
nearly twice as many skates at 2.5 [deg]C as between 4.5 and 9.5 
[deg]C, with catch rates dropping off sharply for temperatures warmer 
than 10 [deg]C (Sosebee et al., in prep). Generally, in U.S. waters 
during spring, adult thorny skate were found at temperatures between 2 
and 13 [deg]C, with the majority between 4 and 7 [deg]C. During the 
fall, they were found over a temperature range of 3 and 13 [deg]C, with 
the majority found between 5-8 [deg]C (Packer et al., 2003). 
Preliminary tagging results are available from a 2016 Gulf of Maine 
study with data from 23 thorny skate with pop-up satellite archival 
transmitting (PSAT) tags. The daily (min/max) temperature records from 
all PSAT-tagged skates indicated that thorny skate occurred in 
temperatures of 4.5-10.5 [deg]C from November to August and have a 
broad temperature tolerance (J. Kneebone, pers. comm.). On the Grand 
Banks, catches of thorny skate are generally highest between 3 and 5 
[deg]C, although catch has concentrated on the warmer edge of the Bank 
since the 1990s (Colbourne and Kulka 2004). A similar concentration on 
the edge of the banks has been observed in the Gulf of St Lawrence, 
correlating with temperatures between 2 and 4 [deg]C (Swain and Benoit, 
2006). Few thorny skates were caught where temperature was <0 [deg]C. 
The available information consistently demonstrates that thorny skate 
are most likely to occur in areas with cooler water temperatures (0 to 
14 [deg]C).
    Seasonal migrations have been noted on the Scotian Shelf and the 
Grand Banks, but are not well understood (NEFSC 2003). Within the Gulf 
of St. Lawrence, skates move into deeper waters in November and 
December and into shallower waters in April and May, with peak numbers 
present there in late summer and fall (Clay 1991; Darbyson and Benoit 
2003). A change in spring and fall distributions results in higher 
density and concentration of biomass in deeper waters during the 
spring, corresponding with areas of warmer temperature in Canadian 
waters (Kulka and Miri 2003). These may be examples of skates seeking 
out their preferred temperature range.
    Few data are available regarding thorny skates' preferred salinity, 
although catch is highest between 32 and 35 practical salinity units 
(PSU) (COSEWIC, 2012). In U.S. waters during the spring, they are 
primarily caught at salinities of 33-34 PSU and in the fall at 
salinities of 32-35 parts per thousand (ppt), with more than 60 percent 
at 33 ppt (Packer et al., 2003). In the Barents Sea, thorny skate are 
caught at a much larger range of salinities than other species (Dolgov 
et al., 2004a).
    Thorny skates eat a varied diet, with smaller skates consuming 
copepods, krill, polychaete worms and amphipods, and larger skates 
eating other fish and larger crustaceans including shrimp and crabs 
(Skjaeraasen and Bergstad 2000; Dolgov 2002). Thorny skate are 
opportunistic feeders; important fish prey species can include cod, 
capelin, and redfish (Pedersen 1995; Dolgov 2002). Within the Gulf of 
Maine, fish make up the majority of the thorny skate diet (Link and 
Sosebee 2011).
    Overall, thorny skate are considered a habitat generalist, found 
over a wide variety of substrates, depths and temperatures. Thorny 
skate vary widely in depth preferences over the range of the species 
(Dolgov et al., 2005a; COSEWIC 2012; Sosebee et al., in prep), likely 
indicating an ability to seek out ideal temperatures.

Life History

    Thorny skate, like other skate, ray and shark species, are 
relatively slow-growing, late to mature and have low fecundity when 
compared to bony fishes. An oviparous (egg-laying) species, they 
reproduce year-round (Kneebone et al., 2007), although more females 
contain mature egg capsules in the summer (Collette and Klein-MacPhee 
2002). In the Gulf of Maine, average egg capsule size is largest in 
October (Sulikowski et al., 2005a). Mature females are estimated to 
produce an average of 40.5 eggs per year, with a hatching success of 38 
percent (COSEWIC 2012). Others have estimated up to 56 eggs per year, 
slightly higher than similar species (McPhie and Campana 2009). 
Incubation time is long and, depending on temperature (low water 
temperatures slow development), is estimated to take from 2.5-3 years 
after deposit (Berestovskii 1994).
    Lifespan for the species is difficult to estimate, due to the slow 
growth of the species and limited number of maximum-sized fish 
available for aging. A limited number of maximum-sized fish may result 
from fishing and natural mortality or from differential capture rates 
for different sized skates. Individuals estimated to be up to 16 years 
of age using vertebral and caudal thorn aging have been observed from 
the Gulf of Maine (Sulikowski et al., 2005b)

[[Page 11543]]

and from Greenland (Gallagher et al., 2006), respectively. Long-term 
tagging indicated these fish may live at least 20 years in Canadian 
waters (Templeman 1984) and further vertebral aging confirmed with 
radiocarbon bomb dating methodology indicated a maximum age of at least 
28 years for individuals caught off the Scotian Shelf (McPhie and 
Campana 2009). Theoretical longevity was estimated at up to 39 years, 
much longer compared to other native skates (McPhie and Campana 2009).
    Total length and length at reproductive maturity vary widely over 
the species' range. Maximum length and length at maturity (L50) 
decrease with increases in latitude. Maximum lengths range from 90 cm 
on the Labrador Shelf to 100-110 cm in the Gulf of Maine (COSEWIC 
2012). The smallest L50s were reported farthest north, with female L50 
reported at 44-47 cm, and male L50 at 44-50 cm reported for skates 
caught around Baffin Island on the Labrador Shelf (Templeman 1987). In 
the Gulf of Maine, L50 for females occurred at approximately 11 years 
and 87.5 cm; for males, L50 was reached at 10.9 years and 85.6 cm 
(Sulikowski et al., 2005b). A later study on the eastern Scotian Shelf 
(midway between these populations) noted that female skates could show 
signs of maturity anywhere from 39.0-74.5 cm and males between 51.0-
78.0 cm (McPhie and Campana 2009). The reasons behind variation in 
total length and length at maturity are unknown but may stem from 
environmental or genetic factors.
    Age at maturity was estimated to be 11 years for females and 10.9 
years for males. Size and age at maturity for thorny skate were greater 
and also demonstrated more variability than for sympatric skate species 
(Sosebee 2005; McPhie and Campana, 2009). Size and maturity were not 
found to correlate with depth (Templeman 1987).
    Overall, thorny skates were found to have the highest potential 
reproductive rate and predicted population increase when compared to 
sympatric skate species (McPhie and Campana 2009); this may indicate a 
greater ability to recover from fishing for thorny skate than for 
similar species. Reproductive rate is still considered low overall 
compared to teleost species.

Population Structure

    Tagging data from both sides of the Atlantic show thorny skates 
remaining in or returning to the same area with 85 percent of 
individuals traveling less than 120 kilometers (km) from their tagging 
locations (Templeman 1984; Walker et al., 1997). In both studies, 13 
percent of individuals traveled longer distances between 180 and 445 
km. Preliminary study results from a 2016 study in the Gulf of Maine 
recovered data from five thorny skates tagged with PSATs in the 
vicinity of Cashes Ledge. The tag results indicated movements of 3-26 
km at 100 days post-tagging (J. Kneebone, pers.comm). Three thorny 
skates tagged offshore in the Gulf of Maine near the Hague line 
exhibited movements of 3.5-6.5 km over 100 days post-tagging. In the 
western Gulf of Maine (Massachusetts Bay), data from 13 PSAT-tagged 
skates indicated distance traveled of 2-30 km over 100-day (n=12) and 
200-day (n=1) tag deployment periods (J. Kneebone, pers. comm.). 
Collectively, these preliminary data corroborate previously published 
data and further demonstrate that thorny skates exhibit limited 
movements in the Gulf of Maine. However, some thorny skates off the 
coast of Newfoundland were observed to travel rapidly, with several 
individuals moving up to 200 km within a few months (Templeman 1984).
    Conventional tagging data have several limitations when it comes to 
accurately monitoring movement for this species, including that all 
returns are produced from commercial fishing gear. First, these data 
rely on recaptures and reporting (commercial/recreational fishermen or 
surveys may report catch of a tagged fish) and the information obtained 
is generally limited to the location where the fish was recaptured in 
relation to where it was originally tagged. Second, the information 
from conventional tagging is limited by the small number of thorny 
skates tagged and recaptured. Return rates in the western Atlantic were 
14 percent (Templeman 1984) and 25 percent in the eastern Atlantic 
(Walker et al., 1997). The prosecution of fisheries in relatively 
shallow waters compared to the depth range of the species limits 
returns and therefore, data, because there are fewer opportunities for 
recapture. A particularly low rate of return of five percent was 
observed for skates tagged offshore (Templeman 1984), making it 
difficult to understand offshore movements. However, based on the 
available information, thorny skates are capable of occasional long 
distance movements, and this may be sufficient to promote reproductive 
mixing across the species' range.
    Comparisons with sympatric skate species suggest that the thorny 
skate has one of the highest levels of haplotype and nucleotide genetic 
diversity when compared to other western Atlantic skate species, 
although this can be skewed by some individuals (Coulson et al., 2011). 
Haplotype and nucleotide diversity are useful metrics for assessing 
species genetic diversity because they can be influenced by factors 
such as the size and age of a population and degree of connectivity 
between populations. High genetic diversity was also detected in 
studies that examined additional genetic markers (Chevolot et al., 
2007, Lynghammar et al., 2014). Overall, barcode gap analysis (an 
analytical tool wherein the barcoding gap is the difference between 
interspecific and intraspecific genetic distance within a group of 
organisms) indicates the genetic distance within the thorny skate 
species is low compared to the average genetic distance within other 
species in the skate family (0.93 v. 3.9 percent, Lynghammar et al., 
2014). This means that, within the skate species sampled, thorny skates 
are genetically more similar to each other, suggesting greater gene 
flow across their range, than all of the other skate species in this 
study.
    Distribution of genetic diversity did not mirror geographic 
distribution in the thorny skate, with the center of the range having 
the highest genetic diversity (Lynghammar et al., 2014). Highest 
diversity in one study occurred between two adjacent sites in the 
eastern Atlantic, and when these were removed, there was no significant 
difference in genetic diversity between remaining sites (Chevolot et 
al., 2007). Thorny skates captured in Iceland had the highest levels of 
diversity with fourteen different haplotypes present; thorny skates 
from the eastern and western Atlantic sites had significantly lower 
levels with three haplotypes each. The distribution of specific genetic 
haplotypes and the depth range of the species likely indicate gene flow 
across the range of the species (Chevolot et al., 2007) and indicate 
that there are not isolated populations, as there is no significant gap 
in distribution across the species' range (COSEWIC 2012).
    Comparisons of haplotype frequencies between the Northwest and 
Northeast Atlantic alone indicated that there was a statistically 
significant difference between haplotype frequencies of thorny skates 
in these two areas; however, when samples from Greenland were included, 
the differences in haplotype frequencies among thorny skates from these 
locations were not statistically significant (Lynghammar et al., 2014). 
Additionally, Greenland represented a higher number of genetic 
haplotypes than either the Northwest or Northeast Atlantic, confirming 
previous results and suggesting that genetic mixing is occurring in the 
center of the species' range (Lynghammar et al., 2014).

[[Page 11544]]

    Further work comparing individuals of different sizes from two 
sites in the Gulf of Maine and two sites in Canadian waters found no 
significant genetic differences (Tsang et al., 2008). Comparison of 
``late maturing'' skates collected mostly north of Newfoundland and 
``early maturing'' skates collected within Canadian waters south of 
Newfoundland also showed no significant genetic differences (Lynghammar 
et al., 2014).
    In summary, current information indicates thorny skates in the 
Northwestern Atlantic comprise a single stock, despite the differences 
in length and length at maturity. Some genetic differentiation is 
present between the Northwest Atlantic and Northeast Atlantic, but the 
center of the range appears to have genetic mixing between these two 
areas. This is likely made possible by the depth range of the species, 
which allows for continuous distribution as there are no known barriers 
to migration.

Abundance and Trends

    The best available information regarding population abundance and 
trends is provided by independent trawl surveys within different 
regions of the species' range. Trawl surveys underestimate thorny skate 
abundance, however, because skates are able to escape capture by 
sliding under the foot rope of trawl gear (Templeman 1984). Capture 
efficiency varies widely with the configuration of the gear and size of 
the fish, as well as area (COSEWIC 2012), making it difficult to 
compare results or pool surveys. In addition, surveys are generally 
conducted to support fisheries management and are designed for other 
(commercial) species and thus may not be optimal for estimating skate 
abundance. In Europe, the areas surveyed do not always overlap with 
areas of known thorny skate abundance, particularly in deeper waters 
(Templeman 1984; Walker and Hislop 1998). Across the species' range, 
available data vary widely in survey gear, timing of surveys, and time 
series, making comparisons between different areas difficult (COSEWIC 
2012).
    Trawl surveys are limited in the types of bottom they can survey. 
For trawls, catch efficiency increases with the smoothness of the 
bottom. The roughest bottoms may be avoided by survey operators to 
prevent gear hang-ups. The increase in number and length of skates 
caught by longline surveys, particularly on rough bottom (Sosebee et 
al., in prep), confirms that trawl gear underestimates total abundance 
and biomass of thorny skates (Dolgov et al., 2005b) because rough 
bottom areas are not as efficiently surveyed with trawl gear.
    The utility of trawl survey data to provide information on the 
thorny skate is thus limited in two ways: By location, missing an 
unknown portion of the species' preferred habitat; and by catch 
efficiency, underestimating the number of skates in surveyed areas. 
Trawl survey data, therefore, are an index and represent a minimum 
estimate of overall thorny skate abundance. Trends are still evident 
from these data but should be viewed with the sampling caveats 
described above, given the lack of information collected beyond the 
survey areas and the unknown proportion of individuals in un-trawlable 
habitat (see Davies and Jonsen 2011).

United States Waters

Northeast Fisheries Science Center Surveys

    In U.S. waters, the relative abundance of the thorny skate is 
measured via NEFSC bottom trawl surveys. The NEFSC trawl survey has 
been conducted in the autumn from the Gulf of Maine to Southern New 
England since 1963 as a method of measuring abundance of groundfish for 
fishery management purposes. A spring survey was started in 1968. The 
autumn surveys provide a longer time series and are used for stock 
assessment purposes.
    Numbers and catch-per-unit-effort (CPUE; abundance or biomass per 
tow) of thorny skates caught by this survey have declined over time. 
After reaching a peak during the 1970s with 5.3 kilogram (kg) per tow 
(2.9 fish per tow) during the spring survey and 5.9 kg per tow (1.8 
fish per tow) in the autumn survey, catch has declined to less than 
five percent of these maximum levels, with the average current CPUE 
from 2013-2015 being 0.17 kg/tow (Sosebee et al., in prep). Average 
length decreased from a high of 63 cm in 1971 to a low of 23 cm in 
2003, but has been stable from 2014-2015 at 40-50 cm. From 1963 to 
2015, minimum swept-area abundance and biomass estimates decreased from 
a high of 10.9 million individuals and 36,393 metric tons (mt) in the 
1966 autumn survey to a low of 518,900 individuals (mean length = 19 
cm) and 365 mt in autumn 2012 and 485,000 individuals (mean length = 30 
cm) and 499 mt in autumn 2013. Spring survey numbers have followed a 
similar trend. Despite the decline from 1970s levels, recent data 
demonstrate increased capture. Survey estimates from 2014-2015 have 
increased from previous lows, with estimates of 865,000 individuals and 
1,264 mt in spring 2015 and 628,000 individuals and 844 mt in autumn 
2015.
    It is important to note that the low efficiency of the gear in 
capturing skate for these surveys (as described above) indicates 
minimum abundance and biomass in the survey area, and true abundance 
and biomass are higher than numbers reflect. Historical survey efforts 
also likely underestimated thorny skate abundance and biomass. Edwards 
(1968) estimates the catch efficiency of thorny skates in the NEFSC 
trawl survey at 0.1. Using this value, the 2015 autumn survey 
represents an estimated 8,440 mt and 6 million fish within U.S. waters 
surveyed by NEFSC (Sosebee et al., in prep).

State Surveys

    Additional surveys in shallow water show similar patterns regarding 
trends of thorny skate biomass and abundance, or fluctuations without 
trend. The Massachusetts Division of Marine Fisheries (MADMF) surveys 
inshore state waters in spring and autumn. Catch of thorny skates is 
variable in this survey (1978 to 2015) but demonstrates an overall 
decreasing trend in thorny skate biomass and abundance. The spring 
index had stabilized around the median of 0.07 kg/tow throughout the 
2000s, but has since declined, and none were caught in 2013. The autumn 
index has generally been below the median of 0.14 kg/tow since 1994. 
Average length of fish in this survey is variable but tends toward 
smaller fish (Sosebee et al., in prep).
    The Maine-New Hampshire Inshore Trawl Survey was established in 
2000. This survey is stratified by depth and demonstrates low abundance 
of thorny skates in the inshore area with little trend over the time 
series (Sosebee et al., in prep).
    The Atlantic States Marine Fisheries Commission shrimp survey 
samples deeper offshore waters within the Gulf of Maine. A decreasing 
trend is evident here in both abundance and biomass of skate for the 
duration of the time series (1985-2015); however, recent survey results 
show stable biomass estimates from 2009-2015. Although average length 
has varied considerably over the time series (1985-2015), in general it 
shows a stable trend (Sosebee et al., in prep).
    Overall, NEFSC bottom trawl surveys indicate that thorny skates are 
most abundant in the Gulf of Maine and Georges Bank offshore strata 
regions, with very few fish caught in inshore (<27 m depth), Southern 
New England, or MA regions (NEFSC 2007, Sosebee et al., in prep). More 
recent surveys (2007-2009) show a broadening of thorny skate

[[Page 11545]]

distribution into deeper water but also a concentration in the western 
Gulf of Maine (Sosebee et al., in prep).

Canadian Waters

    Where data are available, a decrease in abundance has been observed 
since the 1970s in Canadian waters; however, recent data indicate an 
increasing or stable trend in Canadian waters. The thorny skate is 
widely distributed and is the most common skate species in Canadian 
waters. The amount of decrease varies widely between different regions, 
varying from 30 percent on the Southern Labrador Shelf to more than 80 
percent on the Scotian Shelf between 1977 and 2010 (COSEWIC 2012). Over 
the same time period, the average individual weight of commercially 
targeted demersal fish on the Scotian Shelf declined from 41-51 percent 
with the larger decline being on the eastern portion of the shelf 
(Zwanenburg 2000). Most Canadian areas saw a decline in abundance of 
thorny skates between 50-60 percent during this time period (COSEWIC 
2012).
    From 1990 to 2011, survey abundance has been mostly stable on the 
Southern Labrador Shelf and Northern Gulf of St. Lawrence, and has 
increased 61 percent on the Grand Banks (COSEWIC 2012). More recent 
information is available for the Grand Banks region, where a fishery 
persists for skates. Biomass in some Northwest Atlantic Fisheries 
Organization (NAFO) subdivisions has been increasing, but overall 
abundance and biomass remains at low levels, averaging 33,500 tons (t) 
(30,391 mt) from 1993 to 2012 (DFO 2013). Biomass of thorny skates 
overall on the Grand Banks has been stable since 2006 (Simpson et al., 
2016, Nogueira et al., 2015).
    Overall declines in abundance have been higher for larger thorny 
skates (COSEWIC 2012). In Canadian waters around Newfoundland, 
mortality for the smallest thorny skates has declined since the 1970s, 
while mortality has increased for older juveniles and adults in the 
Gulf of St. Lawrence (Swain et al., 2013). Fishing effort in the area 
has declined over the same period; suggesting natural mortality factors 
(not attributable to fishing) are responsible for this change in 
mortality rates. On the Grand Banks, average length has increased since 
the 1990s (Nogueira et al., 2015). Recruitment rate has also increased 
in the Southern Gulf of St. Lawrence since the 1970s (Benoit and Swain 
2011).
    Despite the overall downward trend in abundance of thorny skates 
within Canadian waters throughout the entire time series, recent (mid 
to late 1990s to 2012) trends for abundance, biomass, average length, 
and recruitment rate have been stable and increasing and thorny skates 
remain numerous. Estimated minimum abundance for Canada in 2010 was 
more than 188 million individuals, with recent increases in abundance 
of 61 percent on the Grand Banks (COSEWIC 2012). The true number is 
likely much higher because of the limitations of sampling gear and 
sampling locations and depth (as discussed above). Approximately 30-40 
percent of the species' range lies within Canadian waters (COSEWIC 
2012).

Northeast Atlantic

    The thorny skate is widely distributed and is the most common skate 
species in the Northeast Atlantic. Within the Barents Sea, the 
population abundance was estimated to average 143 million fish and the 
biomass 95,000 mt during the period 1998 through 2001 (Dolgov et al., 
2005a). In Norway, their numbers fluctuated without trend between 1992 
and 2005. They remain the most widely occurring skate species with a 
mean catch rate in Norwegian waters of 55.2 per km\2\ (Williams et al., 
2008). While not directly comparable given differences in tow length 
and capture efficiency of different gears, this is relatively high when 
compared to capture rates in Canada and the United States. In Iceland 
and East Greenland, population estimates are not available, but 
abundance in groundfish surveys has remained stable since 2000. Area 
occupied has likewise remained stable, averaging 50 percent from 2000-
2014 (International Council for the Exploration of the Sea (ICES) 
2015).
    In the North Sea off the coast of Scotland, thorny skates comprise 
eighty percent of the total skate biomass (Walker and Heeseen 1996; 
Piet et al., 2009). Biomass was estimated to be greater than 100,000 t 
(90,718 mt) during the early 1980s (Sparholt and Vinther 1991). 
Abundance of thorny skates in the area increased greatly when comparing 
the 1906-1909 and 1990-1995 time periods, despite the overall decrease 
in landings of skates and rays in this region over the same time period 
(Walker and Hislop 1998). Abundance decreased (1977-2015) but is 
comparable to the abundances observed during the early 1970s (ICES 
2015). Recent abundance estimates of thorny skates in the Northeast 
Atlantic have been stable (ICES 2015).

Area Occupied in the Northwest Atlantic

    Some evidence suggests a contraction of the thorny skate's range 
over time. In Canadian waters, area occupied has remained stable 
through much of the species' range. Populations off Labrador, north of 
Newfoundland and on the St. Pierre Bank have all remained stable. Areas 
south of Newfoundland and St. Pierre Bank have experienced a decline in 
area occupied. On the Grand Banks, area occupied has decreased 
approximately 50 percent from a high of almost 60,000 km\2\ to 
approximately 30,000 km\2\ in 2010 (COSEWIC 2012). It appears fish in 
this area have been avoiding colder waters present on the top of the 
Bank, instead moving towards the warmer edge (Kulka and Miri 2003). In 
the Southern Gulf of St. Lawrence, the area occupied has decreased from 
about 55,000 km\2\ in the mid-1970s to approximately 20,000 km\2\ in 
2010. Meanwhile, within the Northern Gulf of St. Lawrence, the area 
occupied has doubled from 42,300 km\2\ from 1991-1993 to 90,400 km\2\ 
from 2008-2010 (COSEWIC 2012). This supports the conclusion that the 
range of the thorny skate is shifting within the Gulf of St. Lawrence.
    On the Scotian Shelf, area occupancy has declined steadily over the 
time series, by 58 percent since 1970-1972, and 66 percent since 1974-
1976 (when it occupied 150,000 km\2\). The decline ceased in 2000, and 
skate in this area now occupy approximately 50,000 km\2\. There is a 
strong correlation in this location between area occupied and abundance 
(Shackell et al., 2005), indicating that remaining skates are using the 
most suitable habitat. Thorny skate occupancy has also declined on the 
Canadian side of Georges Bank by about 40 percent. Overall, area 
occupied for all areas surveyed off Canada (averages for 2007-2009) is 
approximately 290,000 km\2\, about 90,000 km\2\ less than in the 1970s. 
Most of the decline occurred prior to 1991 with the largest decrease on 
the Scotian Shelf (COSEWIC 2012).
    Within the United States, NEFSC bottom trawl surveys show an 
approximately 75 percent decrease in number of total tows containing 
skate from 1965 to 2008. There is an upward trend in the number of 
positive tows since 2008. There are several distribution indicators of 
possible contractions or expansions in distribution, such as positive 
tows, the Gini index (a measure indicating deviation from equal spatial 
distribution), and design-weighted area of occupancy, which takes into 
account

[[Page 11546]]

the area swept by the tows and the proportion of positive tows. 
Multiple estimates of biomass and abundance versus area also show a 
moderate increase in concentration of fish (Sosebee et al., in prep).
    An example of this is the design-weighted area of occupancy from 
the spring and fall NEFSC surveys, which incorporate a stratified 
random survey design (Kulka 2012). This index takes into account the 
area swept by the tows and the proportion of positive tows (Swain et 
al., 2012). The calculation is the proportion of positive tows within a 
stratum multiplied by the area of that stratum and summed over the 
stock area. For the thorny skate, the design-weighted area of occupancy 
declined over time, from a high of almost 85,800 km\2\ in the mid-1970s 
to 14,000-17,000 km\2\ in 2008. Area occupied has increased recently, 
but concentrations of thorny skates remain within the Gulf of Maine 
(Sosebee et al., in prep).
    Abundance of the thorny skate has declined since the highs of the 
1970s. The areas of greatest decline have been along the southern 
portion of their range, including U.S. waters and Canadian waters of 
the Scotian shelf. Abundance has declined by up to 80 or 95 percent in 
these areas (COSEWIC 2012), although recent surveys show the number of 
thorny skates in these areas are stable or slightly increasing (Sosebee 
et al., in prep; COSEWIC 2012). In more northern parts of the range, 
decline in abundance has been closer to 60 percent on average and 
recent surveys show the number of thorny skates in these areas is 
increasing or stable (ICES 2015).
    Biomass has also decreased, in part due to decreased abundance but 
also due to high average adult mortality. Recent biomass estimates 
indicate stabilization (at low levels) or increasing trends in some 
regions (COSEWIC 2012; Sosebee et al., in prep). Thorny skates remain 
numerous throughout the greater portion of their range, numbering in 
the hundreds of millions (COSEWIC 2012). Due to low catchability, the 
species may be even more numerous than estimates predict. Area occupied 
has declined by approximately half since the 1970s; however, some 
expansion of area occupied has been observed recently and current 
estimates have demonstrated an upward trend in recent years (COSEWIC 
2012; ICES 2015).

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 of any species of vertebrate fish or wildlife which 
interbreeds when mature.'' The term ``distinct population segment'' is 
not recognized in the scientific literature and is not defined in the 
ESA or its implementing regulations. Therefore, the Services adopted a 
joint policy for recognizing DPSs under the ESA (DPS Policy; 61 FR 
4722) on February 7, 1996. Congress has instructed the Secretaries of 
Interior and Commerce to exercise this authority with regard to DPSs `` 
* * * . . . sparingly and only when biological evidence indicates such 
an action is warranted.'' The DPS Policy requires the consideration of 
two elements when evaluating whether a vertebrate population segment 
qualifies as a DPS under the ESA: (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 species or subspecies to which it belongs.
    A population segment of a vertebrate species may be discrete if it 
satisfies either one of the following conditions: (1) It is markedly 
separated from other populations of the same taxon (an organism or 
group of organisms) as a result of physical, ecological, or behavioral 
factors. Quantitative measures of genetic or morphological 
discontinuity may provide evidence of this separation; or (2) it is 
delimited by international governmental boundaries within which 
differences in control of exploitation, management of habitat, 
conservation status, or regulatory mechanisms exist that are 
significant in light of section 4(a)(1)(D) of the ESA (e.g., inadequate 
regulatory mechanisms). If a population segment is found to be discrete 
under one or both of the above conditions, its biological and 
ecological significance to the taxon to which it belongs is evaluated. 
This consideration may include, but is not limited to: (1) Persistence 
of the discrete population segment in an ecological setting unusual or 
unique for the taxon; (2) evidence that loss of the discrete population 
segment would result in a significant gap in the range of a taxon; (3) 
evidence that the discrete population segment represents the only 
surviving natural occurrence of a taxon that may be more abundant 
elsewhere as an introduced population outside its historical range; or 
(4) evidence that the discrete population segment differs markedly from 
other population segments of the species in its genetic 
characteristics.
    The petition from AWI and DW requested that we list a ``Northwest 
Atlantic DPS'' of the thorny skate as threatened or endangered under 
the ESA, or, as an alternative, a ``United States DPS'' as threatened 
or endangered under the ESA.
    In May 2016, we convened an ERA workshop with thorny skate experts. 
The workshop participants provided individual expert opinions regarding 
the available information to assess whether there are any thorny skate 
population segments that satisfy the DPS criteria of both discreteness 
and significance. Data relevant to the discreteness question included 
physical, ecological, behavioral, tagging, and genetic data. As 
described above, the thorny skate is widely distributed across the 
Northern Atlantic, without any significant known gaps or barriers in 
the species range (COSEWIC 2012) or between the Northwest and Northeast 
Atlantic. Likewise, populations are considered contiguous between the 
United States and Canada.
    Conventional tagging data suggest that individual movement is 
limited (Templeman 1984; Walker et al., 1997); however, tagging studies 
to date have been small and relied upon recapture of individuals by 
fishing operations. There is a lack of information regarding species' 
movements in deeper water. However, the long distance movements of some 
tagged individuals (hundreds of kilometers) suggest that occasional 
long distance movements by some individuals may be sufficient to 
promote reproductive mixing across the species' range (Templeman 1984; 
Chevolot et al., 2007). Connectivity between areas is also supported by 
high areas of genetic diversity in the center of the range (Lynghammar 
et al., 2014). There are no physical barriers to thorny skate 
migration, and migratory pathways appear to be present between all 
ocean basins (i.e., connected areas of appropriate habitat). 
Collectively, this information indicates that thorny skates are one 
contiguous population.
    As highlighted in the DPS Policy, quantitative measures of 
morphological discontinuity or differentiation can serve as evidence of 
marked separation of populations. No genetic difference was detected 
between thorny skates caught within Canadian versus U.S. waters (Tsang 
et al., 2008). Best available genetic information (Lynghammar et al., 
2014) suggests a significant amount of genetic diversity between 
populations in the Northwest and Northeast extremes; however, no 
significant difference is found when individuals from the center of the 
range are included, which indicates genetic mixing is occurring in the 
center of the range (Lynghammar et al., 2014). The center of the 
species' range around Iceland and Greenland contains the highest amount 
of genetic diversity,

[[Page 11547]]

with the edges of the species' range in the Northwest and Northeast 
Atlantic both having lower levels of diversity. We do not know if the 
diversity is in neutral genetic markers or is indicative of adaptation. 
It should be noted that Lynghammar et al. (2014) was not specifically 
targeting thorny skates; therefore, improved sampling for thorny skates 
is suggested for future research. However, this study represents the 
best available scientific information on thorny skate genetics.
    In summary, current information indicates thorny skates in the 
North Atlantic comprise a single species, despite the differences in 
age and length at maturity. Some genetic differentiation is present 
between the Northwest Atlantic and Northeast Atlantic, but the center 
of the range bridges genetic diversity between these two areas, 
indicating that there is mixing and gene flow across the range. This is 
likely made possible by the continuous distribution and depth range of 
the species, as there are no known physical barriers to migration. 
Morphological differences in thorny skate populations are limited to 
body size and age at maturity. Comparisons of individuals of different 
sizes from two sites in the Gulf of Maine and two sites in Canadian 
waters found no significant genetic differences (Tsang et al., 2008). 
Comparison of ``late maturing'' skates collected mostly north of 
Newfoundland and ``early maturing'' skates collected within Canadian 
waters south of Newfoundland also found no significant genetic 
differences (Lynghammar et al., 2014).
    Thorny skates are habitat generalists. None of the populations 
appear to occur in an ecological setting unusual or unique for the 
taxon. Thorny skates are well distributed throughout the Atlantic; 
there is no population that represents the only surviving natural 
occurrence of the taxon. Thorny skates do not exist as an introduced 
population outside their historical range.
    A population can be determined to be discrete if it is delimited by 
international governmental boundaries within which differences in 
control of exploitation, management of habitat, conservation status, or 
regulatory mechanisms exist that are significant in light of section 
4(a)(1)(D) of the ESA. A directed fishery for thorny skates is 
permitted in the central portion of the species' range comprising the 
area of the Grand Banks in Canadian waters, as well as Iceland and 
Greenland. Landings of thorny skates are prohibited in the extreme 
western (U.S.) and eastern (U.K. eastward) portions of the species' 
range. In most shallow water areas across the species' range, thorny 
skates undergo some form of fishing mortality because they are a common 
bycatch species. There are some differences in management in the 
Northwestern Atlantic (by the Northwest Atlantic Fisheries Organization 
(NAFO) and the Northeastern Atlantic (by ICES). In 2004, the NAFO 
Fisheries Commission set a total allowable catch (TAC) of 13,500 mt for 
2005-2009 in Division 3 LNO. This TAC was lowered by NAFO to 12,000 mt 
for 2010-2011, and to 8,500 mt for 2012. The TAC was further reduced to 
7,000 mt for 2013, 2014, 2015 (Simpson et al., 2016). In the 
Northeastern Atlantic there is a prohibition against landing thorny 
skates from European Union waters in the Barents Sea and east of the 
United Kingdom (ICES 2015). A very small fishery exists in Iceland and 
off East Greenland, where survey numbers have remained stable since 
2000 (ICES 2015). With populations within the Northeast Atlantic 
currently considered stable (ICES 2015), existing regulatory measures 
appear sufficient to control fishing mortality within this region. 
Iceland reported 1,625 mt of thorny skate landings in 2014. A 2016 EU 
regulation prohibits thorny skate landing for EU waters of ICES 
divisions IIa, IIIa and VIId and ICES subarea IV Subareas II and IV and 
Division IIIa (Norwegian Sea, North Sea, Skagerrak, and Kattegat), 
based on ICES advice that a precautionary approach dictates no targeted 
fishing and measures to reduce bycatch. ICES advice for this species 
west of the UK is currently pending.
    Within U.S. waters, thorny skates are managed under the Magnuson-
Stevens Fishery Conservation and Management Act (MSA). Landings of 
thorny skates within U.S. waters were unregulated until 2003 when the 
New England Fishery Management Council (NEFMC) established a Fishery 
Management Plan (FMP) for the skate complex. In 2003, the stock was 
deemed ``overfished'' and a landing prohibition was put in place, 
requiring all catch of thorny skates to be discarded at sea. Compliance 
with the prohibition against landing thorny and other skates is 
examined via port sampling. While thorny skates are still considered 
overfished within the United States, overfishing is no longer occurring 
(NEFMC 2009), indicating that fishery management measures are 
successfully controlling fishing mortality in those waters.
    Under the Fisheries Act, Canadian fisheries may take thorny skates 
as bycatch in other fisheries, and a small directed fishery still 
operates on the Grand Banks. Available information suggests that catch 
is well below the total allowable catch limits as set by NAFO and 
Canada, indicating fishing mortality is controlled (Simpson et al., 
2016). The Scotian shelf has been closed to directed fishery for skates 
(thorny and winter) since the early 2000s. In addition to compliance 
with catch limits, thorny skate abundance has been stable on the Grand 
Banks and the rest of Canada, yet still below historical levels 
(COSEWIC 2012). Therefore, existing regulatory measures appear 
sufficient to control fishing mortality.
    Throughout its range, thorny skates cross international 
governmental boundaries. There are regulatory mechanisms in place 
across the species' range with respect to conserving and recovering the 
thorny skate. While there are regulatory differences in different parts 
of its range, when evaluated as described further below in the 
Inadequacy of Existing Regulatory Mechanisms section, these regulatory 
mechanisms are adequate and the effects on thorny skates are similar. 
These mechanisms include regulating directed catch and bycatch, and 
result in effective management of the harvest of thorny skates 
throughout their range.
    In summary, thorny skates rangewide exhibit genetic continuity 
between the Northwest and Northeast Atlantic through a high degree of 
diversity in the center of their range, a lack of significant 
differences in control of exploitation, management of habitat, 
conservation status, or regulatory mechanisms across international 
borders. We have determined that neither thorny skates in the United 
States nor thorny skates in the Northwest Atlantic are discrete from 
thorny skates throughout the rest of the North Atlantic.
    The workshop participants provided their individual expert opinions 
regarding the best available information related to the discreteness 
criterion for thorny skates. Upon our review of their individual 
analyses and the DPS policy, we have concluded that there are no 
populations of the thorny skate that are discrete. Because we do not 
find any populations that are discrete, we do not go on to the second 
element of the DPS criteria (significance). Therefore, none of the 
segments suggested by the petitioners (i.e., Northwest Atlantic or 
United States) qualifies as a DPS. Because there are no DPSs of the 
thorny skate, the workshop participants next provided their individual 
expert opinions regarding extinction risk rangewide for the thorny 
skate.

[[Page 11548]]

Assessment of Extinction Risk

    The ESA (section 3) defines endangered species as ``any species 
which is in danger of extinction throughout all or a significant 
portion of its range.'' A threatened species is ``any species which is 
likely to become an endangered species within the foreseeable future 
throughout all or a significant portion of its range.'' 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 currently in danger of extinction throughout all or a 
significant portion of its range (endangered) or likely to become so in 
the foreseeable future (threatened). We evaluate both demographic 
risks, such as low abundance and productivity, and threats to the 
species, including those related to the factors specified by the ESA 
sections 4(a)(1)(A)-(E).

Methods

    As described above, we convened a workshop of invited experts to 
provide individual input regarding extinction risk to the species. This 
section discusses the methods used to evaluate demographic factors, 
threats, and overall extinction risk to the species now and in the 
foreseeable future. For this assessment, the term ``foreseeable 
future'' was defined as 40 years. The workshop participants reviewed 
other comparable assessments (which used generation times of either one 
or two generations) and provided their expert opinions on the 
appropriate timeframe for the thorny skate. Each of the workshop 
participants considered thorny skate generation time (16 years), the 
ability to predict population trends, climate-modeling predictions, and 
the time for management actions to be realized and reflected in 
abundance trends when considering a foreseeable future timeline. The 
individual workshop participants determined that, for the thorny skate, 
there was reasonable confidence across this time-period (40 years) that 
the information on threats and management is accurate. We agree that, 
because of the factors listed above, this is a reasonable definition of 
``foreseeable future'' for the thorny skate, and we use the same 
definition here.
    Often the ability to measure or document risk factors is limited, 
and information is not quantitative or very often is lacking 
altogether. Therefore, in assessing risk, it is important to include 
both qualitative and quantitative information. In previous NMFS status 
reviews, Biological Review Teams have used a risk matrix method, 
described in detail by Wainwright and Kope (1999), to organize and 
summarize the professional judgement of a panel of knowledgeable 
scientists. 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. 
Connectivity refers to rates of exchange among populations of 
organisms. 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 workshop participants each evaluated 
demographic risks by individually assigning a risk score to each of the 
four demographic criteria (abundance, growth rate/productivity, spatial 
structure/connectivity, diversity). The scoring for the demographic 
risk criteria corresponded to the following values: 1--very low risk, 
2--low risk, 3--moderate risk, 4--high risk, and 5--very high risk. A 
demographic factor (or viable population descriptor) was ranked very 
low if it was unlikely that this descriptor contributed significantly 
to risk of extinction, either by itself or in combination with other 
viable population descriptors. A factor was ranked low risk if it was 
unlikely that this descriptor contributed significantly to long-term or 
near future risk of extinction by itself, but there was some concern 
that it may, in combination with other viable population descriptors. A 
factor was ranked moderate risk if this descriptor contributed 
significantly to long-term risk of extinction, but did not in itself 
constitute a danger of extinction in the near future. A factor was 
ranked high risk if this descriptor contributed significantly to long-
term risk of extinction and was likely to contribute to short-term risk 
of extinction in the near future, and a factor was ranked very high 
risk if this descriptor by itself indicated danger of extinction in the 
near future.
    Each workshop participant scored each demographic factor 
individually. Each workshop participant identified other demographic 
factors and/or threats that would work in combination with factors 
ranked in the higher categories to increase risk to the species. During 
the workshop, the participants provided their expert opinions for each 
of the demographic risks, including considerations outlined in McElhany 
et al. (2000) and the supporting data on which it was based. Workshop 
participants were given the opportunity to adjust their individual 
scores, if desired, after the workshop. The scores were then tallied, 
reviewed, and considered in our overall extinction risk determination. 
As noted above, this scoring was carried out for the species rangewide.
    Each workshop participant also performed a threats assessment for 
the thorny skate by evaluating the impact that a particular threat was 
currently having on the extinction risk of the species. Threats 
considered included habitat destruction, modification, or curtailment; 
overutilization; disease or predation; inadequacy of existing 
regulatory mechanisms; and other natural or manmade threats, because 
these are the five factors identified in section 4(a)(1) of the ESA. 
Workshop participants each ranked the threats for the thorny skate at a 
range-wide scale. The workshop participants used the ``likelihood 
point'' (FEMAT) method to allow individuals to express uncertainty in 
determining the contribution to extinction risk of each threat to the 
species. Each workshop participant was allotted five likelihood points 
to rank each threat. Workshop participants individually ranked the 
severity of each threat through the allocation of these five likelihood 
points across five ranking criteria ranging from a score of ``very low 
contribution'' to ``very high contribution.'' The scoring for the 
threats correspond to the following values: 1--very low contribution, 
2--low contribution, 3--moderate contribution, 4--high contribution, 
and 5--very high contribution. A threat was given a rank of very low if 
it is unlikely that this threat contributes significantly to risk of 
extinction, either by itself or in combination with other threats. That 
is, it is unlikely that the threat will have population-level impacts 
that reduce the viability of the species. A threat was ranked as low 
contribution if it is unlikely that this threat contributes 
significantly to long-term or near future risk of extinction by itself, 
but there is some concern that it may, in combination with other 
threats. A threat was ranked as medium contribution if this threat 
contributes significantly to long-term risk of extinction, but does not 
in itself constitute a danger of extinction in the near future. A 
threat was ranked high contribution if this threat contributes 
significantly to long-

[[Page 11549]]

term risk of extinction and is likely to contribute to short-term risk 
of extinction in the near future. Finally, a threat was ranked very 
high contribution if the threat by itself indicates a danger of 
extinction in the near future. Detailed definitions of the risk scores 
can be found in the status review report (NMFS 2017).
    Similar to the demographic parameters, the workshop participants 
were asked to identify other threat(s) and/or demographic factor(s) 
that may interact to increase the species' extinction risk. The 
workshop participants also considered the ranking with respect to the 
interactions with other factors and threats. For example, workshop 
participants identified that threats due to the inadequacy of existing 
regulatory mechanisms may interact with the threat of overutilization 
and slow population growth rates (a demographic factor) to increase the 
risk extinction.
    Workshop participants were asked to rank the effect that the threat 
was currently having on the extinction risk of the species. Each 
workshop participant could allocate all five likelihood points to one 
ranking criterion or distribute the likelihood points across several 
ranking criteria to account for any uncertainty. Each individual 
workshop participant distributed the likelihood points as she/he deemed 
appropriate with the condition that all five likelihood points had to 
be used for each threat. Workshop participants also had the option of 
ranking the threat as ``0'' to indicate that, in their opinion, there 
was insufficient data to assign a score, or ``N/A'' if in their opinion 
the threat was not relevant to the species either throughout its range 
or for individual stock complexes. When a workshop participant chose 
either N/A (Not Applicable) or 0 (Unknown) for a threat, all five 
likelihood points had to be assigned to that category only.
    During the group discussion, the workshop participants were asked 
to identify other threat(s) or demographic factor(s) that were 
interacting with the threats or demographic factors to increase the 
species' extinction risk. As scores were provided by individual 
workshop participants, each individual stated his or her expert opinion 
regarding each of the threats, and the supporting data on which it was 
based. We considered these along with the demographic scores in our 
overall risk assessment.
    The workshop participants were then asked to use their informed 
professional judgment to individually qualitatively score overall 
extinction risk for the thorny skate. The results of the demographic 
risks analysis and threats assessment, described below, informed this 
ranking. For this analysis, the workshop participants used three levels 
of extinction risk, consistent with the NMFS (2016) listing guidance: 
Low risk, moderate risk, and high risk. Low risk was defined as: ``A 
species or DPS is at low risk of extinction if it is not at moderate or 
high level of extinction risk (see ``Moderate risk'' and ``High 
risk''). A species or DPS may be at low risk of extinction if it is not 
facing threats that result in declining trends in abundance, 
productivity, spatial structure, or diversity. A species or DPS at low 
risk of extinction is likely to show stable or increasing trends in 
abundance and productivity with connected, diverse populations.'' 
Moderate risk was defined as: ``A species or DPS is at moderate risk of 
extinction if it is on a trajectory that puts it at a high level of 
extinction risk in the foreseeable future (see description of ``High 
risk''). A species or DPS may be at moderate risk of extinction due to 
projected threats or declining trends in abundance, productivity, 
spatial structure, or diversity. The appropriate time horizon for 
evaluating whether a species or DPS will be at high risk in the 
foreseeable future depends on various case- and species-specific 
factors. For example, the time horizon may reflect certain life history 
characteristics (e.g., long generation time or late age-at-maturity) 
and may also reflect the time frame or rate over which identified 
threats are likely to impact the biological status of the species or 
DPS (e.g., the rate of disease spread). (The appropriate time horizon 
is not limited to the period that status can be quantitatively modeled 
or predicted within predetermined limits of statistical confidence. The 
biologist (or Team) should, to the extent possible, clearly specify the 
time horizon over which it has confidence in evaluating moderate 
risk.).'' High Risk was defined as: ``A species or DPS with a high risk 
of extinction is at or near a level of abundance, productivity, spatial 
structure, and/or diversity that places its continued persistence in 
question. The demographics of a species or DPS at such a high level of 
risk may be highly uncertain and strongly influenced by stochastic or 
depensatory processes. Similarly, a species or DPS 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 imminent and substantial demographic risks.''
    The workshop participants adopted the ``likelihood point'' method 
for ranking the overall risk of extinction to allow individual workshop 
participants to express uncertainty. For this approach, each workshop 
participant distributed 10 `likelihood points' among the extinction 
risk categories (that is, each workshop participant had 10 points to 
distribute among the three extinction risk categories). Uncertainty is 
expressed by assigning points to different risk categories. For 
example, a workshop participant would assign all 10 points to the `low 
risk' category if he/she was certain that the definition for `low risk' 
was met. However, he/she might assign a small number of points to the 
`moderate risk' category and the majority to the `low risk' category if 
there was a low level of uncertainty regarding the risk level. The more 
points assigned to one particular category, the higher the level of 
certainty. This approach has been used in previous NMFS status reviews 
(e.g., Pacific salmon, Southern Resident killer whale, Puget Sound 
rockfish, Pacific herring, black abalone, and common thresher shark) to 
structure the workshop participant'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. The workshop participant 
scores were tallied, discussed, and summarized by NMFS for the thorny 
skate rangewide.
    The workshop participants did not make recommendations as to 
whether the species should be listed as threatened or endangered. 
Rather, the workshop participants drew scientific conclusions about the 
overall risk of extinction faced by the thorny skate under present 
conditions and in the foreseeable future (as noted above, defined as 40 
years) based on his/her evaluation of the species' demographic risks 
and assessment of threats.

Evaluation of Demographic Risks

    Abundance: The workshop participants individually evaluated the 
available thorny skate abundance information, which is summarized in 
the Abundance section of the listing determination. Several workshop 
participants noted that the available information indicated thorny 
skate abundance had declined significantly from historical levels in 
certain parts of its range. However, in all regions where abundance 
trends and/or indicators are

[[Page 11550]]

available, declines appear to have been halted, and increases in 
abundance were apparent in some regions. Further declines are unlikely 
due to improved management. Abundance estimates from the Northwest 
Atlantic are currently in the millions of individuals, even where 
significant declines have occurred. There is no evidence of depensatory 
processes such as reduced likelihood of finding a mate, and recruitment 
per spawner has remained stable for thorny skate. The mean score we 
calculated based on the workshop participants' individual scores 
corresponds to a very low to low ranking rangewide, as this factor is 
unlikely to contribute significantly to the thorny skate's risk of 
extinction.
    Growth rate/productivity: The workshop participants individually 
evaluated the available information on thorny skate life history traits 
as they relate to this factor. As summarized in the Reproduction, 
Growth, and Demography section, thorny skates have low inherent 
productivity due to their late age at maturity, low fecundity, slow 
population growth rates, and long generation times (16 years). This low 
productivity makes thorny skate populations vulnerable to 
overexploitation, and slow to recover from depletion. The mean score we 
calculated based on the workshop participants' scores corresponds to a 
low to moderate ranking rangewide, as this factor is unlikely to 
contribute significantly to the thorny skate's risk of extinction.
    Spatial structure/connectivity: The workshop participants 
individually evaluated the available information on thorny skate 
spatial structure (tagging and genetics information) summarized in the 
Population section. The thorny skate has a very broad range, including 
across the entire North Atlantic Ocean. The species is mobile, and some 
connectivity across the range is apparent from both tagging and 
genetics data. At the southern edges, there is an indication that a 
contraction or northward shift may be occurring; however, recent 
surveys show an increase in abundance in the southern range in U.S. 
waters. The mean score we calculated based on the workshop 
participants' individual scores corresponds to a very low to low 
ranking rangewide, as this factor is very unlikely to contribute 
significantly to the thorny skate's risk of extinction.
    Diversity: The workshop participants individually evaluated the 
available information on thorny skate diversity summarized in the 
Population section. The available genetics studies indicate that thorny 
skate populations have the highest genetic diversity amongst skate 
species, and there is reproductive connectivity along a continuum 
rangewide. Therefore, genetic diversity appears to be sufficiently high 
and not indicative of isolated or depleted populations. The thorny 
skate does not appear to be at risk due to substantial changes or loss 
of variation in life history traits, population demography, morphology, 
behavior, or genetic characteristics. The mean score we calculated 
based on the workshop participants' individual scores corresponds to a 
very low to low ranking rangewide, as this factor is very unlikely to 
contribute significantly to the thorny skate's risk of extinction.

Evaluation of Threats

    The workshop participants identified several threats in the low to 
moderate category for contribution to extinction risk, including: 
Climate change, manmade non-fishing habitat impacts, commercial 
discards, commercial landings, global and national climate regulation, 
and inadequacy of existing NAFO regulations. Both climate change and 
global or national climate change regulations received the most 
likelihood points in the moderate contribution to extinction risk 
category. Only one threat, climate change, received likelihood points 
in the high contribution category, but the majority of points were in 
the low to moderate category. We summarize the threats to the thorny 
skate and provide the workshop participants' expert opinions on their 
degree of contribution to extinction risk.
    Habitat Destruction, Modification, or Curtailment: Workshop 
participants individually evaluated the available information on 
habitat use and distributions of the thorny skate summarized in the 
status review report. Overall, the thorny skate is a habitat generalist 
in the marine environment, and not substantially dependent on any 
particular habitat type. It occurs in coastal and offshore waters, and 
is not dependent during any life stage on more vulnerable estuarine 
habitats. Thorny skate habitat use is influenced by temperature and 
prey distributions, but they have broad temperature tolerances and an 
opportunistic diet, making them less vulnerable to habitat destruction.
    Within the Northwest Atlantic, the species' range from Greenland 
south is a mixing zone for different currents. The Labrador Current 
flows down the inner shelf, bringing cooler and fresher water from the 
north, which flows down over the ocean shelves, including the Grand 
Banks, Scotian Shelf, Georges Bank and into the Gulf of Maine. 
Meanwhile, the Gulf Stream in deeper offshore waters brings warmer, 
saltier water up from the south (Saba et al., 2015). The range of the 
thorny skate covers both of these currents and the mixing zone; thorny 
skates are able to occur throughout this area due to their tolerance of 
different temperatures. This mixing zone makes it difficult to predict 
the impacts of climate change within the area, although recent specific 
modeling suggests that the Gulf of Maine will warm nearly three times 
as fast as other areas from a predicted northward shift in the Gulf 
Stream (Saba et al., 2015). Recently, the Labrador Current has had the 
opposite effect, decreasing salinity in the shallower parts of the Gulf 
of Maine and cooling temperatures on the shelves (Townsend et al., 
2010). Overall, waters within the range of the thorny skate are 
expected to get warmer, increase in salinity and decrease in pH (Saba 
et al., 2015). In marine ecosystems, climate change impacts like these 
are generally expected to push species distributions northward 
(Frumhoff et al., 2007), but possible effects on the thorny skate are 
unclear.
    In U.S. waters, the thorny skate has experienced a relatively high 
amount of range contraction as measured during NEFSC surveys. A small 
but statistically significant northward shift in range, and increased 
concentration in deeper waters has been detected (Nye et al., 2009). A 
possible explanation of the consistent, long-term decline of thorny 
skates in the NEFSC trawl survey is skates are shifting out of the 
survey area. The shift in area occupied on the Grand Banks in Canada 
may also be a response to climate change. In this area, skates have 
shifted to the warmer edge of the banks, avoiding the cooler 
temperatures present on the center of the banks (Kulka and Miri 2003) 
created by the Labrador Current. The lack of skates present in 
temperatures below 1 or 2[deg] C supports this conclusion.
    There is no information regarding the impacts of ocean 
acidification on the thorny skate. However, a study on the sympatric 
little skate, Leucoraja erinacea, demonstrates that changes in 
temperature and acidic concentration can result in complex effects on 
developmental time, body condition and survival in skate hatchlings (Di 
Santo 2015). There is currently no information available on how hypoxia 
or changes in nutrient composition might impact the thorny skate. Given 
its broad range, generalist feeding habits, and ability to move, 
localized areas of hypoxia or low prey availability are unlikely to 
have an impact at a species level.

[[Page 11551]]

    Since climate change impacts are expected to shift species 
distributions northward and impact species diversity, recent studies 
have focused on the impacts of climate change to fish community 
assemblages, particularly on species richness and diversity. Some 
impacts have been observed for ``coastal'' or shallow water communities 
(<200 m/656 ft in depth) in the Gulf of St. Lawrence (Tamdrari et al., 
2014) and Iceland (Stefansdottir et al., 2010). In both these studies, 
thorny skates were found to associate more with the deeper water fish 
assemblages, which had only minor, if any, impacts from climate change.
    There is some evidence that suggests the species is shifting to 
deeper waters. Thorny skates comprised 7.97 percent of fish in the 
``coastal'' species assemblage (<200m) in the early 1990s and only 5.58 
percent on average from 2004-2010 in the Gulf of St. Lawrence. In the 
deeper species assemblage (>200m) they went from 3.71 percent in the 
early 1990s to 4.52 percent averaged from 2004-2010 (Tamdrari et al., 
2014). This is a relatively small change for both depths when compared 
to change for other species, representing half as much decrease in the 
coastal assemblage as redfish (Sebastes spp.) and an order of magnitude 
less than the decrease in Atlantic cod (Gadus morhua). Additionally, 
thorny skates were most abundant between 100 and 350 m of depth before 
climate change became apparent (McEachran and Musick 1975), and this 
remains the case in modern surveys (Packer et al., 2003; COSEWIC 2012), 
though depths in the fall range up to 500 m in U.S. waters (Packer et 
al., 2003).
    Recent climate vulnerability analyses have been performed for fish 
species in the Northeast United States and for fish assemblages on the 
Scotian Shelf in Canada. Despite having similar methodologies, these 
studies came to different conclusions regarding the vulnerability of 
thorny skates to climate change. Stortini et al. (2015) rated the 
vulnerability of the thorny skate on the Scotian shelf as ``low.'' This 
study scaled the estimated vulnerability relative to thirty-two other 
species found on the Scotian Shelf; therefore, the ``low'' 
vulnerability rating is in relation to other species in that location.
    Hare et al. (2016) rated this species as having a ``high'' 
biological sensitivity and climate exposure likelihood off the 
Northeast United States, on a scale of ``low'' to ``very high.'' In 
this effort, vulnerability was equated to the likelihood of the species 
experiencing either reduced productivity or shifting its distribution 
out of the region in response to climate change. This vulnerability 
analysis concluded that there was also a ``high'' chance of negative 
impacts and changes in species distribution within its U.S. range. Both 
assessments used a similar variety of species life history factors to 
produce a species sensitivity score, but Hare et al., (2016) used a 
larger variety of climate factors including pH, salinity, precipitation 
and ocean currents to determine climate exposure, whereas Stortini et 
al. (2015) looked only at mean temperature under different warming 
scenarios.
    While thorny skates in U.S. waters are at high risk for being 
impacted by climate change (likely to manifest as loss of cold water 
habitat in U.S. waters), the best available information indicates that 
throughout most of the range, the generalist habitat requirements of 
the thorny skate will limit impacts of climate change. This conclusion 
is supported by studies on species diversity that indicate impacts to 
species assemblages have not yet occurred on communities including the 
thorny skate, due to its depth preferences (Stefansdottir et al., 2010, 
Tamdarai et al., 2015). In addition, modeling predicts a less than 10 
percent loss of thermally appropriate habitat before 2030 in U.S. 
waters, but almost no habitat loss before 2030 in Canadian waters 
(Shackell et al., 2014). A ten percent loss is expected in Canada and 
up to 25 percent loss in U.S. waters may occur before 2060 (Shackell et 
al., 2014). Although the risk may be high that thorny skates will shift 
their distribution out of Northeast U.S. waters due to warming ocean 
conditions (Hare et al., 2016), the species would have the ability to 
persist in adjacent regions with more suitable habitat.
    Ocean temperature changes due to climate change may be contributing 
to a contraction of the thorny skate's range at its southern edges. 
Thorny skates appear to have comparatively low exposure to potentially 
harmful pollutants, and there is no information suggesting their 
individual fitness or populations are threatened by pollution. The mean 
score we calculated based on the workshop participants' individual 
scores indicates that climate change and non-fishing related 
modifications to habitat (e.g. drilling, offshore windfarm 
construction) present a low to moderate contribution to extinction 
risk.
    Overutilization: The workshop participants individually evaluated 
the available information on fishing mortality and abundance trends of 
thorny skate summarized in the status review report. Overutilization 
for commercial purposes was once considered one of the primary threats 
to thorny skate populations. Significant declines have been documented 
throughout much of the thorny skate's range due to historical fishing 
pressure. The most recent information suggests that declines in several 
stocks have halted due to fishing restrictions (COSEWIC 2012; ICES 
2015; Sosebee et al., in prep). Populations appear to be stable or 
slowly increasing, with millions of individuals remaining in the 
Northwest Atlantic alone. Therefore, there appears to be a low 
likelihood of further population declines because of stabilization 
observed after management actions were put into place. The mean score 
we calculated based on the workshop participants' individual scores 
corresponds to a very low or low ranking for all threats in this 
category, with the commercial landings and commercial discards 
receiving mean scores of slightly higher than low contributions to 
overall extinction risk.
    Thorny skates were and are taken as bycatch by fisheries throughout 
their range, including those in the North Sea, Barents Sea, Gulf of St. 
Lawrence and on the Canadian and U.S. continental shelves. Targeted 
fisheries, particularly by foreign fleets including those of Spain, 
Portugal and Russia, developed in the 1990s (COSEWIC 2012; Sosebee et 
al., in prep). The fishery for thorny skates was largely unregulated in 
the Northwest Atlantic until the 2000s (COSEWIC 2012). Currently, small 
fisheries exist in the North Sea (Piet et al., 2009) and on the Grand 
Banks in Canada (Simpson et al., 2016), which is, as mentioned earlier, 
the first regulated skate fishery in international waters. Since 2003, 
U.S. vessels have been prohibited from possessing or landing thorny 
skates (NEFMC 2009). While directed fisheries on the species are 
currently limited, thorny skates continue to be taken as bycatch and 
discarded in commercial fisheries within their range.

U.S. Fisheries Catch and Bycatch

    Total landings for all skate species within U.S. waters reached 
9,462 mt in 1969 and declined after that, reaching a low of 847 mt in 
1981 (Sosebee et al., in prep). Skate landings increased substantially 
after that time period for lobster bait and export, rising to a high of 
20,342 mt in 2007 (Sosebee et al., in prep). Estimated total catch of 
thorny skates has declined from over 5,000 mt in the late 1960s and 
early 1970s to about 200-300 mt in recent years (Sosebee et al., in 
prep). Thorny skates make up a small overall portion of skate catch, 
particularly in comparison to winter and little skates. Most of the

[[Page 11552]]

early catch (1969-1989) was from otter trawl discards, while landings 
dominated from 1990 to present (Sosebee et at., in prep). Discards from 
scallop dredges increased in proportion to population estimates during 
the late 1970s and again during the late 1990s (Sosebee et al., in 
prep). While landings were generally low, catch of thorny skates likely 
contributed to the decline of the species over time.
    In 2003, the NEFMC implemented a FMP for the seven skates present 
within the Gulf of Maine. The FMP prohibited landings of thorny skates 
as the stock status was considered overfished (NEFMC 2009). The limited 
information regarding species biomass required the NEFSC to develop 
survey-based overfished and overfishing reference points for the thorny 
skate: ``Thorny skate is in an overfished condition when the three-year 
moving average of the autumn survey mean weight-per-tow is less than 
one half of the 75th percentile of the mean weight-per-tow observed in 
the autumn trawl survey from the selected reference time series. 
Overfishing occurs when the three year moving average of the autumn 
survey mean weight per tow declines 20% or more, or when the autumn 
survey mean weight per tow declines for three consecutive years. The 
reference points and selected time series may be re-specified through a 
peer reviewed process and/or as updated stock assessments are 
completed'' (NEFMC 2009). The target biomass for thorny skates is 
currently set at 4.13 kg/tow and the minimum biomass threshold at 2.06 
kg/tow. The most recent 3-year average remains below these figures at 
0.17 kg/tow; however, this figure has remained steady since 2011.
    The MSA states: ``A stock or stock complex is considered 
``overfished'' when its biomass has declined below a level that 
jeopardizes the capacity of the stock or stock complex to produce 
Maximum Sustainable Yield (MSY) on a continuing basis. MSY is defined 
as the largest long-term average catch or yield that can be taken from 
a stock or stock complex.'' The overfished/overfishing status of a 
stock is determined relative to its ability to produce continued yield 
from a fishery. The overfished status of thorny skates within the 
United States means that fishing mortality rates (including past 
landings and discards) have been too high, and caused the population to 
decline below acceptable levels. The stock must be rebuilt to biomass 
levels that can produce MSY for a fishery to be sustainable. The 
prohibition on harvest in U.S. waters is expected to help the stock 
rebuild. This means any thorny skates caught within U.S. waters must be 
discarded at sea.
    Estimated thorny skate discards are low relative to other skates 
(Sosebee et al., in prep). Landings and dead discards have decreased in 
recent years (2007-2014) and total discards have stabilized or 
increased.

Canadian Fisheries and Bycatch

    Thorny skates comprise the majority of skates caught in commercial 
fisheries in Canada. The majority of thorny skate catch comes from the 
coast of Labrador and Newfoundland, including the Grand Banks area. 
This has ranged from a high of approximately 24,000 mt in the early 
1990s to current levels around 6,000 mt. Relative fishing mortality has 
remained stable (1985- 2009) in this area at approximately ten percent 
(COSEWIC 2012).
    Within the southern Gulf of St. Lawrence, estimated landings of 
thorny skates peaked in 1994 at approximately 38 t, and have since 
decreased to an average 1-2.7 t over the period 2006-2011(Benoit 2013). 
The thorny skate is the most common discarded skate species. On 
average, 490 t were discarded in the early 1990s, this dropped to 53.7 
t on average over the period 2006 -2011 (Benoit 2013). While the 
majority of discards in the past came from trawl fisheries, currently 
half are from trawl and half from the gillnet fishery for Greenland 
halibut (Benoit 2013). Overall fishing effort in this area has declined 
or remained stable since the 1990s (COSEWIC 2012).
    The only remaining directed fishery for the thorny skate is 
executed within the Grand Banks Area. This area is managed between two 
areas, 3Ps directly south of Newfoundland and entirely within the 
Canadian Exclusive Economic Zone (EEZ), and divisions 3LNO, which 
comprise the outer banks, some of which lies outside the Canadian EEZ. 
Quota regulation within the EEZ was enacted in 1995 (Simpson et al., 
2014). In 2004, NAFO enacted quota regulation for the entire 3LNO area, 
making this the first regulated skate fishery in the world in 
international waters. The regulated areas include areas within and 
outside the Canadian EEZ; 3Ps remained under Canada's quota system. For 
most years since the quotas were enacted, catch has remained well below 
the limits. Relative fishing mortality within the Grand Banks has 
decreased over time. Within the 3LNO it increased from the late 1980s 
to a peak of 29 percent in 1997; then stabilized at approximately 17 
percent during 1998-2004 (Simpson et al., 2016). In 2005, relative 
fishing mortality declined to 4 percent and has remained around 5 
percent (Simpson et al., 2016). Since 1985, fishing mortality within 
3Ps was relatively constant, below 5 percent for most years (Simpson et 
al., 2016).

Northeast Atlantic Fisheries and Bycatch

    There is little directed fishing effort on thorny skates across 
most of the Northeast Atlantic, with a prohibition against landings 
currently in place in European Union waters in the Barents Sea and east 
of the United Kingdom (ICES 2015). There is a small fishery landing 
thorny skates from Iceland and Greenland. Landings here have increased 
but still remain below 2,000 mt, or about half that of Canada's yearly 
landings.
    The available information indicates that current thorny skate 
populations are numerous in many areas and that area occupied is 
increasing. While the portion of the population within the United 
States is not currently capable of sustaining a fishery, fisheries for 
thorny skates are well-controlled throughout the range. Fishing 
mortality relative to biomass has decreased across the range through 
time, and is currently rather low in most areas. The mean score we 
calculated based on the workshop participants' individual scores 
indicate that commercial landings across the range of the species 
present a low contribution to extinction risk.
    We have also considered the best available information on the 
mortality rates of thorny skates that are discarded (i.e., returned to 
the water alive after capture in fishing gear). Factors that impact 
thorny skate discard survival in trawl fisheries include size, depth of 
capture, difference in temperature between bottom and surface 
conditions (Benoit et al., 2013), duration of the tow and degree of 
injury sustained during the capture event (Mandelman et al., 2013). 
Skates can have an overall high survival rate following discard, with 
up to 20 percent mortality predicted for trawl fisheries within the 
Gulf of St. Lawrence (Benoit, 2013). Mandelman et al. (2013) studied 
the post-discard mortality of thorny skates captured in trawl gear in 
the Gulf of Maine. This study indicates that while 72-hour post-discard 
mortality of a sample of individuals retained in captivity following 
cage trials was only 22 percent, the condition of many of the 
individual thorny skates was poor (52 percent injury rate at time of 
capture; most with listless appearance and lack of vigor at the end of 
the 72-hour period) and 7-day mortality was 66 percent. The authors 
note that the species may be less resilient than

[[Page 11553]]

indicated by the 22 percent 72-hour mortality rate and cautions against 
the use of the 22 percent mortality rate in management. The effects of 
captivity on these mortality rates are unknown; however, it is 
reasonable to expect that captivity contributed to slightly higher 
mortality rates. The available information indicates a low to moderate 
risk of mortality to a thorny skate once it is captured (Benoit et al., 
2013 and Mandelman et al., 2013). The elimination of most directed 
fisheries and reductions in catches are expected to reduce overall 
fishing mortality, including discard mortality. It is also important to 
note that post-discard mortality is considered in developing fishing 
management policies for the thorny skate in the United States. Current 
management measures consider the available information on post-discard 
mortality. While overutilization had been a primary threat to the 
species, fishing mortality is being managed throughout the species' 
range. The available information indicates that current thorny skate 
populations are numerous in many areas and that area occupied is 
increasing. While the portion of the population within the United 
States is not currently capable of sustaining a fishery, fisheries for 
thorny skates are well-controlled throughout the range. Fishing 
mortality relative to biomass has decreased across the range through 
time, and is currently low in most areas. The mean score we calculated 
based on the workshop participants' individual scores indicates that 
commercial discards across the range of the species represent a low 
contribution to overall extinction risk.
    Disease and Predation: Workshop participants individually evaluated 
the available information on disease and predation of thorny skates 
summarized in the status review report. Overall, there is minimal 
information available with which to evaluate these threats. In general, 
thorny skates may be susceptible to diseases, but there is no evidence 
that disease has ever caused declines in populations. The mean score we 
calculated based on the workshop participants' individual scores 
indicates that disease represents a very low contribution to overall 
extinction risk, as it is very unlikely that this threat contributes or 
will contribute to the decline of the species.
    Regarding predation, there is no indication that this species would 
be threatened by excessive predation pressure. Egg capsules for the 
species are reportedly preyed upon by halibut, Greenland shark and 
goosefish (Collette and Klein-MacPhee 2002). Gastropods may also 
predate on egg cases, with a predicted predation frequency ranging from 
4 to 18 percent (Cox et al., 1999). It is unknown what the effect of 
this predation may be, but it could contribute to a slower rate of 
rebuilding.
    Skates, including thorny skates, are prey for a number of species: 
Flounder, other skates, seabirds, marine mammals, sharks, cod and other 
large demersal fishes, with the last being the most important 
(Morissette et al., 2006). Overall mortality for small skates has 
decreased while increasing for larger skates since the 1970s. 
Currently, recruitment for smaller skates remains high in portions of 
the Canadian range (Benoit and Swain 2011; Swain et al., 2013). 
Meanwhile, the numbers of large fishes have decreased. Fishing pressure 
has also decreased, substantially in some regions, indicating sources 
of adult skate mortality may be natural. Marine mammal predation, 
particularly by gray seals, has been suggested as an increasing cause 
of mortality for some locations (Swain et al., 2013).
    Thorny skates are at least a minor source of prey for gray seals, 
composing up to 6 percent of their diet depending on age and season 
(Beck et al., 2007). Gray seal energy requirements are high enough that 
this predator may be responsible for much of the natural mortality of 
adult thorny skates in some areas, despite the thorny skate being a 
minor prey source (Swain et al., 2013, Benoit et al., 2011). Energetics 
modeling has been found to explain a similar pattern of increased adult 
mortality in other local species (Benoit et al., 2011). Further 
modeling work found a negative relationship between the gray seal index 
and thorny skate numbers in the Southern Gulf of St. Lawrence. The harp 
seal index was more likely to explain population trends in the 
Northwest portion of the Gulf. Predation by either species was not 
found to explain trends in thorny skate within the northeast portion of 
the Gulf (Ouellet et al., 2016).
    Predation by gray seals may have increased within the range of the 
thorny skate. Gray seal populations have recovered during the same time 
period of decreasing mortality for small thorny skates. Numbering only 
15,000 individuals in the 1960s, the gray seal population increased to 
350,000 by 2007. In 2014, the population estimate within the Canadian 
range and Gulf of Maine had increased to 505,000 (Hamill et al. 2014). 
In addition, gray seals have been expanding their range and are now 
present in small numbers as far south as Southern New England 
(DiGiovanni Jr. et al., 2016).
    Gray seals stay mostly local (within 50 km) to haul-out sites and 
forage in mostly shallow depths (~100 m) (McConnell et al., 1999, 
Schreer et al., 2001). The largest numbers of gray seals are found in 
the Gulf of St. Lawrence and on Sable Island off the coast of Nova 
Scotia, where they may impact skates on the Scotian Shelf. Smaller 
populations are found in coastal Nova Scotia, Seal Island, Maine and on 
Cape Cod, Massachusetts (Hamill et al., 2014). If gray seal predation 
is contributing to thorny skate mortality, the impact is likely to be 
concentrated in the shallowest portions of the thorny skate range 
around major gray seal population areas.
    Harp seals migrate to the Gulf of St. Lawrence to whelp before 
returning to Artic waters on the overlapping range of thorny skate. 
They migrate along the coast of Labrador and Greenland northward. Small 
numbers of harp seals may remain year-round in southern waters, with 
the majority living in the Artic. Currently there is no evidence that 
thorny skates comprise more than an incidental portion of the harp seal 
diet. Harp seal reproductive rates decreased in the latest assessment, 
with 8.3 million individuals estimated in 2008 and 7.7 million 
estimated in 2012 (DFO 2012). Harp seal predation on thorny skates is 
likely stable or slightly decreasing and centered around whelping 
sites.
    Modeling indicates marine mammal predation may contribute to high 
natural mortality of adult thorny skates in some discrete areas, 
suppressing recovery of their populations (DFO 2012). For now, high 
levels of recruitment in small skates are still evident despite this 
pressure. Recent abundance of thorny skates has also been stable in 
areas where marine mammal populations are centered. The recent 
population increase of gray seals in U.S. waters and coinciding 
stabilization of thorny skate abundance indices suggests that seal 
predation was not likely responsible for thorny skate declines. The 
mean score we calculated based on the workshop participants' individual 
scores indicates that predation represents a very low contribution to 
extinction risk, as it is very unlikely that this threat contributes or 
will contribute to the decline of the species.
    Inadequacy of Existing Regulatory Mechanisms: The workshop 
participants individually evaluated the available information on 
fisheries management regulations and abundance trends of the thorny 
skate summarized in the status review report. The inadequacy of 
regulatory mechanisms to control the harvest of thorny skates was once 
considered a significant threat to their populations. Legal protections 
for

[[Page 11554]]

thorny skates vary between outright prohibitions on landings in the 
United States and much of the Northeast Atlantic, with limited fishing 
permitted in Canada and Iceland.

U.S. Regulations

    Within U.S. waters, thorny skates are managed under the MSA. 
Landings of thorny skates within U.S. waters were unregulated until 
2003 when the NEFMC established an FMP for the skate complex. At that 
time, the stock was deemed ``overfished'' and a landing prohibition was 
put in place, requiring all catch of thorny skates to be discarded at 
sea. At that time, the same prohibitions were put into place for the 
sympatric species, barndoor and smooth skates, to help rebuild these 
stocks. The skate complex FMP does still allow catch of other skate 
species, and other fisheries may also catch thorny skates but are 
likewise required to discard them.
    MSA regulations are enforced in U.S. waters by the U.S. Coast 
Guard, NOAA's Office of Law Enforcement and state partners. Fishermen 
who do not comply with regulations established under the MSA are 
subject to fines and criminal penalties, depending on the severity of 
the offense. Compliance with the prohibition against landing thorny and 
other skates was examined via port sampling. In 2005, 3.61 percent of 
skate wing landings were identified as thorny skate. In the years 
since, this declined rapidly with less than 1 percent of wings 
identified as thorny skate in 2007, and further declined to 0.01 
percent in 2012, indicating that compliance with the discard 
regulations and misidentifications or mislabeling is not an issue in 
the United States (Curtis and Sosebee 2015). While the thorny skate is 
still considered overfished within the United States, overfishing is no 
longer occurring (NEFMC 2009), indicating that fishery management 
measures are successfully controlling fishing mortality in those 
waters.

Canadian Regulations

    Under the Fisheries Act, Canadian fisheries may take thorny skates 
as bycatch in other fisheries, and a small, directed fishery still 
operates on the Grand Banks. Available information suggests that catch 
is well below the total allowable catch limits as set by NAFO and 
Canada, indicating fishing mortality is controlled (Simpson et al., 
2016). The Scotian shelf has been closed to directed fishery for skates 
(thorny and winter) since the early 2000s. In addition to compliance 
with catch limits, thorny skate abundance has been stable on the Grand 
Banks and the rest of Canada, yet still below historical levels 
(COSEWIC 2012). Recruitment in this portion of the species' range 
remains relatively high. Therefore, existing regulatory measures appear 
sufficient to control fishing mortality.

Northeast Atlantic Regulations

    There is a prohibition against landing thorny skates from European 
Union waters in the Barents Sea and east of the United Kingdom (ICES 
2015). A very small fishery exists in Iceland and off East Greenland, 
where survey numbers have remained stable since 2000 (ICES 2015). With 
populations within the Northeast Atlantic currently considered stable 
(ICES 2015), existing regulatory measures appear sufficient to control 
fishing mortality within this region. Iceland reported 1625 t of thorny 
skate landings in 2014. A 2016 EU regulation prohibits thorny skate 
landings in EU waters of ICES divisions IIa, IIIa and VIId and ICES 
subarea IV Subareas II and IV and Division IIIa (Norwegian Sea, North 
Sea, Skagerrak, and Kattegat), based on ICES advice that a 
precautionary approach dictates no targeted fishing and measures to 
reduce bycatch. ICES advice for this species west of the UK is 
currently pending. Thorny skates taken from these EU waters are counted 
under a regional EU skate quota that lacks a robust scientific basis. 
EU limits on these species have been generally trending toward more 
precautionary over the last decade.
    Legal protections for thorny skates vary between outright 
prohibitions on landings in the United States and much of the Northeast 
Atlantic, with limited fishing permitted in Canada and Iceland. While 
thorny skates are also a bycatch species within many fisheries, stable 
population numbers indicate existing protections are sufficient through 
its range. The mean score we calculated based on workshop participants' 
individual scores for both global/national climate change regulations 
and NAFO fishing regulations indicate that inadequacy of these 
regulations represents a low to moderate contribution to extinction 
risk. However, workshop participants also noted uncertainty related to 
other global or national environmental regulations in this category 
because there is more uncertainty in their effectiveness to result in 
protections for marine ecosystems.

Other Natural or Manmade Factors Affecting the Thorny Skate's Continued 
Existence

    The workshop participants individually evaluated the available 
information on other potential threats as summarized in the status 
review report. Natural threats focused on the thorny skate's inherent 
biological vulnerability, which is also reflected in the demographic 
factors described above. The species has low productivity because of 
its life history characteristics and is vulnerable to exploitation and 
population perturbations. Populations can be quickly depleted and take 
many years to recover. However, their mobility, high genetic diversity, 
and generalist habitat and diet strategy contribute to a low risk of 
extinction. The mean scores we calculated based on workshop 
participants' individual scores indicate that both manmade catastrophic 
events and stochastic events represent very low contributions to 
extinction risk because of the wide geographic distribution of the 
species.

Summary of Demographic Factors and Threats Affecting Thorny Skate

    Both demographic factors and threats were qualitatively ranked on a 
scale from very low to very high by the workshop participants (NMFS 
2017). No demographic factors or threats were ranked high or very high. 
Abundance, diversity and spatial structure/connectivity were ranked 
very low to low, and growth rate/productivity was ranked low to 
moderate risk. For the workshop participants' threats assessments, both 
climate change and global or national climate change regulations 
received the most likelihood points in the moderate contribution to 
extinction risk category. Only one threat, climate change, received 
likelihood points in the high contribution category, though the 
majority of points were in the moderate contribution category. No 
threats considered by workshop participants were given an overall 
average score of medium, high or very high contributions to extinction 
risk of thorny skate. All workshop participants placed their individual 
point allocations in the very low contribution to extinction risk 
category for the following threats: Recreational fishing, recreational 
discards, educational collection, and stochastic events.
    The only demographic factor ranked above low was growth rate/
productivity (low to moderate risk). The thorny skate's life history 
traits make the populations vulnerable to threats and slow to recover 
from depletion. Once we compiled the individual workshop participant 
scores and calculated the mean score, only six threats were ranked in 
the low to moderate category, all others were in the very low to low 
categories. The threats ranked low to moderate included: Climate 
change,

[[Page 11555]]

manmade non-fishing habitat impacts, commercial discards, commercial 
landings, global and national climate regulation, and inadequacy of 
existing NAFO regulations. Fishing for thorny skates is managed 
throughout the species' range. Efforts to manage the harvest of the 
species include regulations put forth by the United States, Canada, 
NAFO, and ICES, though workshop participants expressed uncertainty in 
the adequacy of NAFO regulation. Due to these recent management 
efforts, thorny skate abundance has stabilized in the several regions 
(e.g., United States, South Labrador Shelf, North Gulf of St. Lawrence, 
Norway) and has increased in some waters (e.g. Grand Banks). Given its 
life history traits, return to historical abundances may take decades, 
but demographic risks are mostly low and significant threats have been 
reduced.

Overall Risk Summary

    As described previously, the workshop participants used a 
``likelihood analysis'' to evaluate the overall risk of extinction. 
Each workshop participant had 10 likelihood points to distribute among 
the following overall extinction risk categories: Low risk, moderate 
risk or high risk.
    Overall, the mean scores we calculated based on the workshop 
participants' individual scores indicate that rangewide, thorny skates 
have a 93.3 percent likelihood of being at low risk of extinction, 6.6 
percent likelihood of moderate risk of extinction, and 0 percent 
likelihood of high risk of extinction.
    The mean scores we calculated based on the workshop participants' 
individual scores indicate that, overall, the thorny skate is at low 
risk of extinction. None of the workshop participants indicated that 
there was any likelihood of the thorny skate having a high risk of 
extinction. Additionally, there was very little likelihood of a 
moderate risk of extinction (4 points out of 60 total).
    Thorny skates have been subjected to considerable fishing pressure 
for many decades, but improved fisheries management efforts in recent 
years have reduced fishing mortality rates on thorny skate stocks, and 
populations are no longer declining. Return to historical abundance may 
take decades, but demographic risks are mostly low and significant 
threats have been reduced. Based upon the available information 
summarized here, the mean scores we calculated based on the workshop 
participants' individual scores indicate that the thorny skate has a 
low risk of extinction, assuming the dominant threats to its 
populations continue to be managed. We have no reason to believe that 
these dominant threats will not continue to be managed.
    We have independently reviewed the best available scientific and 
commercial information, including the status review report (NMFS 2017) 
and other published and unpublished information. We conclude that the 
thorny skate is not in danger of extinction or likely to become so in 
the foreseeable future throughout its range. As described earlier, an 
endangered species is ``any species which is in danger of extinction 
throughout all or a significant portion of its range'' and a threatened 
species is one ``which is likely to become an endangered species within 
the foreseeable future throughout all or a significant portion of its 
range.'' The workshop participants individually ranked the demographic 
criteria and the five factors identified in the ESA, completed an 
assessment of overall extinction risk, and each submitted his/her 
individual expert opinions to us. We reviewed the results of the ERA 
and concurred with the workshop participant's individual expert 
opinions regarding extinction risk. We then applied the statutory 
definitions of ``threatened species'' and ``endangered species'' to the 
ERA results and other available information to determine if listing the 
thorny skate was warranted.
    The mean scores we calculated based on the ERA workshop participant 
scores indicate that the level of extinction risk to the thorny skate 
is low, with 93.3 percent of the workshop participants' likelihood 
points allocated to the ``low risk'' category. The workshop 
participants allocated only 6.6 percent of their likelihood points to 
the ``moderate extinction risk'' category. Given this low level of 
extinction risk, which is based on an evaluation of the contribution of 
the thorny skate's demographic parameters and threats to extinction 
risk, we have determined that the thorny skate does not meet the 
definition of an endangered or threatened species and, as such, listing 
under the ESA is not warranted at this time.

Significant Portion of Its Range

    Though we find that the thorny skate rangewide is not in danger of 
extinction now or in the foreseeable future, under the SPR Policy, we 
must go on to evaluate whether these species are 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).
    When we conduct an SPR analysis, we first identify any portions of 
the range that warrant further consideration. The range of a species 
can theoretically be divided into portions in an infinite number of 
ways. However, there is no purpose to analyzing portions of the range 
that are not reasonably likely to be significant or in which a species 
may not be endangered or threatened. To identify only those portions 
that warrant further consideration, we 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; 
July 1, 2014). 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.
    If this preliminary determination identifies a particular portion 
or portions for potential listing, those portions are then fully 
evaluated under the ``significant portion of its range'' authority as 
to whether the portion is both biologically significant and endangered 
or threatened. In making a determination of significance, we consider 
the contribution of the individuals in that portion to the viability of 
the species. That is, we determine whether the portion's contribution 
to the viability 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.
    The SPR policy further explains that, depending on the particular 
facts of each situation, we 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' '' (79 FR 37587). Thus, if the answer to 
the first question is negative--whether it addresses the significance 
question or

[[Page 11556]]

the status question--then the analysis concludes, and listing is not 
warranted.
    As described previously, we determined that there are no DPSs of 
the thorny skate, and rangewide, the thorny skate is at a low risk of 
extinction. Applying the SPR policy to the thorny skate, we first 
evaluated whether there is substantial information indicating that any 
portions of the species' range may be significant. After a review of 
the best available information and invited experts' opinions, as 
described below, we find that the data do not indicate any portion of 
the thorny skate's range as being more significant than another. Thorny 
skates are distributed across the North Atlantic and have very few 
restrictions governing their movements. Movements are restricted by 
depth and temperature; however, there are no known gaps in suitable 
habitat, thus allowing a continuous range. Because the Northwest 
Atlantic and the Northeast Atlantic are the two largest portions of the 
species' range, the workshop participants individually considered the 
SPR questions related to abundance, productivity, spatial distribution, 
and diversity outlined in the NMFS listing guidance. As explained 
below, we determined that neither the Northwest Atlantic nor the 
Northeast Atlantic were significant portions. Given that neither the 
Northwest Atlantic nor the Northeast Atlantic represents a significant 
portion of the range, we do not find that thorny skate in U.S. waters 
represent a significant portion of the range of the thorny skate. The 
following questions related to significance of portions were 
considered:
Abundance
     Without that portion, would the level of abundance of the 
remainder of the species cause the species to be at moderate or high 
risk of extinction due to environmental variation or anthropogenic 
perturbations (of the patterns and magnitudes observed in the past and 
expected in the future)?
     Without that portion, would the abundance of the remainder 
of the species be so low, or variability in abundance so high, that it 
would be at moderate or high risk of extinction due to depensatory 
processes?
     Without that portion, would abundance of the remainder of 
the species be so low that its genetic diversity would be at risk due 
to inbreeding depression, loss of genetic variation, or fixation of 
deleterious alleles?
     Without that portion, would abundance of the remainder of 
the species be so low that it would be at moderate or high risk of 
extinction due to its inability to provide important ecological 
functions throughout its life-cycle?
     Without that portion, would the abundance of the remainder 
of the species be so low that it would be at risk due to demographic 
stochasticity?
Productivity
     Without that portion, would the average population growth 
rate of the remainder of the species be below replacement such that it 
would be at moderate or high risk of satisfying the abundance 
conditions described above?
     Without that portion, would the average population growth 
rate of the remainder of the species be below replacement such that it 
is unable to exploit requisite habitats/niches/etc. or at risk due to 
depensatory processes during any life-history stage?
     Without that portion, would the remainder of the species 
exhibit trends or shifts in demographic or reproductive traits that 
portend declines in the per capita growth rate, which pose a risk of 
satisfying any of the preceding conditions?
Spatial Distribution
     Will the loss of one or more of the portions significantly 
increase the risk of extinction to the species as a whole by making the 
species more vulnerable to catastrophic events such as storms, disease 
or temperature anomalies?
     Will connectivity between portions of the species' range 
be maintained if a portion is lost (e.g., does the loss of one portion 
of the range of the species create isolated groups or populations?)?
     Are there particular habitat types that the species 
occupies that are only found in certain portions of the species' range? 
If so, would these habitat types be accessible if a portion or portions 
of the range of the species are lost?
     Are threats to the species concentrated in particular 
portions of the species' range and if so, do these threats pose an 
increased risk of extinction to those portions' persistence?
Diversity
     Will unique genetic diversity be lost if a portion of the 
range of the species is lost?
     Does the loss of this genetic diversity pose an increased 
risk of extinction to the species?
    As described more fully in the status review report and below, the 
workshop participants individually answered ``no'' to all of the 
abundance, productivity and diversity questions related to whether the 
Northwest Atlantic or the Northeast Atlantic portion represent a 
significant portion of the species' range. One workshop participant 
answered ``yes'' to two spatial distribution questions.
    Given estimates of 1.8 billion animals in Northwest Atlantic 
waters, which represent 30-40 percent of the overall population, loss 
of the Northwest Atlantic population would have a large impact on the 
species rangewide, but would not put the species at a moderate or high 
risk of extinction because of the remaining large population size and 
wide geographic distribution. When considering productivity, the group 
noted that the average growth rate for the species does not depend on 
the growth rate in the Northwest Atlantic and vice versa for the 
Northeast Atlantic and that the areas do not exhibit source-sink 
dynamics. There was no evidence that without either area the average 
population growth rate of the remainder of the species would drop below 
replacement, resulting in the population being unable to exploit 
requisite habitat, nor was there any evidence that the remainder of the 
species would be at risk due to depensatory processes. Regarding shifts 
in demographic or reproductive traits, the group could not identify 
evidence that a decline in the Northwest Atlantic would result in a 
decline in the Northeast Atlantic. Given the large spatial distribution 
of the thorny skate and the foreseeable future of 40 years, the group 
could not identify a stochastic event that could impact the entire 
Northwest Atlantic or Northeast Atlantic distribution of the thorny 
skate. There is no information to suggest that loss of any portion 
would severely fragment and isolate the species to the point where 
individuals would be precluded from moving to suitable habitats or have 
an increased vulnerability to threats. The loss of either the Northwest 
Atlantic population or the Northeast Atlantic population would result 
in the loss of connectivity rangewide, given that it is a continuous 
population. However, loss of the Northwest Atlantic population would 
not affect spatial connectivity of the Northeast Atlantic population 
and vice versa. Some genetic differentiation is present between the 
Northwest and Northeast Atlantic, but the central portion of the range 
appears to bridge diversity between these two areas. This is likely 
made possible by the continuous distribution and depth range of the 
species. There is no substantial evidence to indicate that the loss of 
genetic diversity from one portion of the species' range would result 
in the remaining populations lacking enough

[[Page 11557]]

genetic diversity to allow for adaptations to changing environmental 
conditions. Based on the best available genetic research, thorny skates 
have the highest genetic diversity out of 15 studied skate species 
(Lynghammar et al., 2014), and the highest diversity occurs in waters 
near Iceland and Greenland. Due to the genetic diversity present in 
thorny skates across the species' range, loss of either the Northeast 
Atlantic population or Northwest Atlantic population would not present 
a significant increase in the extinction risk to the species.
    The petitioners identified the U.S. population as a potential DPS. 
As noted above, this portion does not qualify as a DPS. We considered 
whether U.S. waters could be a significant portion of the species' 
range. However, due to the workshop participants individual expert 
opinions related to abundance, productivity, spatial distribution, and 
diversity questions for the larger Northwest Atlantic and Northeast 
Atlantic populations and our findings that neither of these constitute 
a significant portion of the species' range, and given the United 
States represents only a small portion of the global range of the 
thorny skate, there is little evidence for concluding that the U.S. 
population is significant to the entire species under the SPR policy. 
Furthermore, there is no indication that loss of the U.S. portion of 
the species' range would result in a moderate or high extinction risk 
to the global species. As was mentioned previously, the available 
population and trend data do not indicate that past declines in the 
United States have affected global populations of thorny skate. Thus, 
the United States population would not qualify as ``significant'' under 
the SPR Policy. Likewise, there is no substantial evidence to indicate 
that the loss of genetic diversity from one portion of the species' 
range would result in the remaining populations lacking enough genetic 
diversity to allow for adaptations to changing environmental 
conditions. Similarly, there is no information to suggest that loss of 
any portion would severely fragment and isolate the species to the 
point where individuals would be precluded from moving to suitable 
habitats or have an increased vulnerability to threats. In other words, 
loss of any portion of its range would not likely isolate the species 
to the point where the remaining populations would be at risk of 
extinction from demographic processes.
    In summary, areas exhibiting source-sink dynamics, which could 
affect the survival of the species, were not evident in any part of the 
thorny skate's range. There is also no evidence of a portion that 
encompasses aspects that are important to specific life history stages, 
but another portion that does not, where loss of the former portion 
would severely impact the growth, reproduction, or survival of the 
entire species. 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. It is important to 
note that the overall distribution of the thorny skate is still 
uncertain. As better data become available, the species' distribution 
(and potentially significant portions of its range) will become better 
resolved. However, at this time, there is no evidence to suggest that 
any specific portion of the species' range has increased importance 
over another with respect to the species' survival. We reviewed the 
individual workshop participants' expert opinions and application of 
the SPR policy. We conclude that under the SPR policy, the preliminary 
determination that a portion of the species' range may be both 
significant and endangered or threatened has not been met. Therefore, 
listing the thorny skate based on it being threatened or endangered in 
a significant portion of its range is not warranted under the SPR 
policy.

Final Determination

    Section 4(b)(1) of the ESA requires that listing determinations be 
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, information 
submitted in response to the 90-day finding (80 FR 65175; October 28, 
2015), the status review report (NMFS 2017), and other published and 
unpublished information cited herein, and we have consulted with 
species experts and individuals familiar with the thorny skate. We 
identified no DPSs of the thorny skate and therefore considered the 
species rangewide. We considered each of the section 4(a)(1) factors to 
determine whether any one of the factors contributed significantly to 
the extinction risk of the species. We also considered the combination 
of those factors to determine whether they collectively contributed 
significantly to extinction risk. As previously explained, we could not 
identify any portion of the species' range that met both criteria of 
the SPR policy. 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 range.
    We conclude that the thorny skate is not in danger of extinction, 
nor is it likely to become so in the foreseeable future throughout all 
or a significant portion of its range. We summarize the factors 
supporting this conclusion as follows: (1) The species is broadly 
distributed over a large geographic range within the North Atlantic 
Ocean, with no barrier to dispersal; (2) genetic data indicate that 
populations are not isolated and that the species has high genetic 
diversity, (3) while the species possesses life history characteristics 
that increase its vulnerability to overutilization, overfishing is not 
currently occurring within the range; (4) the best available 
information indicates that abundance and biomass has stabilized 
rangewide and on the edge of the range in U.S. waters; (5) current 
thorny skate populations are numerous in many areas and the area 
occupied is increasing; (6) while the current population size has 
declined from historical numbers, the population size is sufficient to 
maintain population viability into the foreseeable future and consists 
of at least millions of individuals; (7) a main threat to the species 
is fishery-related mortality from incidental catch (bycatch); however, 
there are strict management measures in place to minimize this threat 
throughout the species' range, and these measures appear to be 
effective in addressing this threat as evidenced by stabilizing numbers 
of thorny skates; (8) there is no evidence that disease or predation is 
contributing to increasing the risk of extinction; and (9) 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.
    Since the thorny skate is not in danger of extinction throughout 
all or a significant portion of its range or likely to become so within 
the foreseeable future, it does not meet the definition of a threatened 
species or an endangered species. Therefore, the thorny skate does not 
warrant listing as threatened or endangered at this time.
    Thorny skates in the Atlantic Ocean from West Greenland to New York 
were

[[Page 11558]]

identified as a NMFS ``species of concern'' in 2006. A species of 
concern is one for which we have concerns regarding status and threats 
but for which insufficient information is available to indicate a need 
to list the species under the ESA. In identifying species of concern, 
we consider demographic and genetic diversity concerns; abundance and 
productivity; distribution; life history characteristics and threats to 
the species. Given the information presented in the status review 
report and the findings of this listing determination, we are removing 
the thorny skate from the ``species of concern'' list.

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: February 21, 2017.
Alan D. Risenhoover,
Acting Deputy Assistant Administrator for Regulatory Programs, National 
Marine Fisheries Service.
[FR Doc. 2017-03644 Filed 2-23-17; 8:45 am]
BILLING CODE 3510-22-P