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Amblyraja radiata. The IUCN Red List of Threatened Species 2020

Authors:
David W Kulka at Fisheries and Oceans Canada
David W Kulka
Jim Ellis at Centre for Environment, Fisheries and Aquaculture Science
Jim Ellis
Brooke N Anderson at Saltwater Inc.
Brooke N Anderson
  • Saltwater Inc.
Charles F Cotton at SUNY Cobleskill
Charles F Cotton
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Abstract

Redist assessment for Thorny Skate
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The IUCN Red List of Threatened Species™
ISSN 2307-8235 (online)
IUCN 2020: T161542A124503504
Scope(s): Global
Language: English
Amblyraja radiata, Thorny Skate
Assessment by: Kulka, D.W., Ellis, J., Anderson, B., Cotton, C.F., Derrick, D.,
Pacoureau, N. & Dulvy, N.K.
View on www.iucnredlist.org
Citation: Kulka, D.W., Ellis, J., Anderson, B., Cotton, C.F., Derrick, D., Pacoureau, N. & Dulvy, N.K.
2020. Amblyraja radiata. The IUCN Red List of Threatened Species 2020: e.T161542A124503504.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
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THE IUCN RED LIST OF THREATENED SPECIES™
Taxonomy
Kingdom Phylum Class Order Family
Animalia Chordata Chondrichthyes Rajiformes Rajidae
Scientific Name:ÊÊAmblyraja radiata (Donovan, 1808)
Synonym(s):
• Raia scabrata Garman, 1913
• Raja radiata Donovan, 1808
Regional Assessments:
• Europe
Common Name(s):
• English: Thorny Skate, Starry Ray
Taxonomic Source(s):
Fricke, R., W.N. Eschmeyer and R. Van der Laan (eds.). 2020. Eschmeyer's catalog of fishes: Genera,
species, references. Available at:
http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp. (Accessed: March
2020).
Taxonomic Notes:
McEachran and Dunne (1998) moved this species from genus Raja to Amblyraja.
Assessment Information
Red List Category & Criteria: Vulnerable A2bcd ver 3.1
Year Published: 2020
Date Assessed: July 1, 2019
Justification:
The Thorny Skate (Amblyraja radiata) is a medium-sized (to 111 cm total length) skate occurring in the
North Atlantic from South Carolina (USA) to Greenland, Iceland, Ireland, United Kingdom, Norway, and
to Russia. It is demersal on continental and insular shelves and slopes from nearshore to 1,400 m
depths, usually at 25–440 m. This skate is genetically indistinguishable throughout its range, yet it
exhibits marked life history differences on either side of the Atlantic and in different parts of the
Northwest Atlantic, growing more slowly, maturing later and reaching a larger maximum size in the
southern extent of their Northwest Atlantic distribution. The generation length is 16 years in the
Northwest Atlantic (south) and 10.6 years elsewhere. It was subject to intensive target fisheries in the
Northwest Atlantic and taken as bycatch in mainly trawl, but also longline and gillnet, fisheries in the
USA and Canadian waters south of the Laurentian Channel (Georges Bank and Scotian Shelf). In the USA,
commercial retention of Thorny Skate was banned 2003, but it is still taken as bycatch and discarded
from trawl fisheries. In Canada on the Scotian Shelf, target fisheries ended in 2002 and any bycatch is
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
1
now discarded. In the Northeast Atlantic, this skate has limited value and it is generally discarded and
has a low discard mortality. Population trends and management vary widely, resulting in different status
and trends throughout its range. On both sides of the Atlantic, the southern-most populations of this
boreal species have shifted northward in response to climate-change induced habitat shifting and
alteration, which, in combination with earlier intensive fishing, resulted in very steep declines (>80%
reduction in three generations) in the most southerly parts of its distribution. At more northerly
latitudes, earlier levels of exploitation have ceased or greatly decreased resulting in recovery and
increasing abundance. Overall, Thorny skate has undergone an estimated population reduction of
30–49% over the last three generation lengths (32–48 years) due the combination of exploitation with
habitat shifting and alteration due to climate change at lower latitudes while, further north, earlier
levels of exploitation that have ceased or greatly decreased and it is assessed as Vulnerable A2bcd.
Previously Published Red List Assessments
2009 – Vulnerable (VU)
https://dx.doi.org/10.2305/IUCN.UK.2009-2.RLTS.T161542A5447511.en
Geographic Range
Range Description:
Thorny Skate is found in the North Atlantic ranging from South Carolina, USA to Greenland, Iceland,
Ireland, United Kingdom, Norway, extending through the Barents Sea to Russia (Last et al. 2016).
Country Occurrence:
Native, Extant (resident): Belgium; Canada (Labrador, New Brunswick, Newfoundland I, Nova Scotia,
Nunavut, Québec); Denmark; Faroe Islands; France (France (mainland)); Germany; Greenland; Iceland;
Ireland; Netherlands; Norway; Russian Federation (European Russia); Svalbard and Jan Mayen; Sweden;
United Kingdom (Great Britain, Northern Ireland); United States (Connecticut, Delaware, Maine,
Massachusetts, New Hampshire, New Jersey, New York, North Carolina, South Carolina, Virginia)
FAO Marine Fishing Areas:
Native: Atlantic - northwest
Native: Atlantic - northeast
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
2
Distribution Map
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
3
Population
There are no data available on the absolute global population size of Thorny Skate. Population trend
data were analyzed over three generation lengths using a Bayesian state-space framework (Sherley et al.
2020, Winker et al. 2020). This analysis yields an annual rate of change, a median change over three
generation lengths, and the probability of the most likely IUCN Red List category percent change over
three generations (see the Supplementary Information). These time-series exhibit striking variation and
were grouped into six regions.
• Northwest Atlantic (south) comprised of four time-series: (a) Southern Gulf of St. Lawrence (4T) trawl
survey index of abundance of mature individuals) (1971–2018), (b) Scotian Shelf and Bay of Fundy
(4VWX) trawl survey index of abundance of mature individuals (1970–2017), (c) Georges Banks,
Canada/Gulf of Maine, USA (5Z) relative abundance trawl survey index of mature individuals
(1970–2017), and (d) the standardized catch-per-unit-effort (CPUE) data from the USA Northeast
Fisheries Science Centre (NEFSC) Fall survey (1963–2018) (D.W. Kulka unpubl. data 2020, compiled from
Fisheries and Oceans Canada, and NOAA USA).
• Northwest Atlantic (north) comprised of three time-series: (a) Newfoundland and Labrador Shelf
(2J3K) Fall trawl survey CPUE of mature individuals (1977–2017), (b) Grand Banks (3LNOPs) Spring trawl
survey CPUE of mature individuals (1973–2017), and (c) Northern Gulf of St. Lawrence (4RS) trawl
survey index of abundance of mature individuals (1991–2018) (D.W. Kulka unpubl. data 2020, compiled
from Fisheries and Oceans Canada, and NOAA USA).
• North central Atlantic (west Greenland) comprised of two time-series from the Greenland Shrimp and
Fish survey in West Greenland trawl survey of abundance of individuals (millions) (1992–2017) (Nygaard
and Nogueira 2019).
• North central Atlantic (Iceland) comprised of two time-series from the Iceland Spring and Autumn
trawl survey indices of biomass (1986–2020) (MFRI 2020).
• Northeast Atlantic (south) comprised of two time-series from the North Sea International Bottom
Trawl Survey in Quarter 1 and 3 in (Groundfish Areas 1 to 4 and 6 to 9) nominal CPUE of individual per
hour (1980–2020) (J.R. Ellis unpubl. data 2020, compiled from the Database of Trawl Surveys DATRAS).
• Northeast Atlantic (north) comprised of two time-series from two swept area based indices of total
biomass (metric tonnes) from (a) the Barents Sea Ecosystem Survey (2003-2016) and (b) the Coastal
Survey along the Norwegian coast (north of 62°N) (2003–2016) (Knutsen et al. 2017).
First, the trend analysis of the four time-series from the Northwest Atlantic (south) reveal very steep
annual rates of decline of 6.5%, consistent with an estimated median decline of 96% over three
generation lengths (48 years), with the highest probability of >80% reduction over three generation
lengths (see Supplementary Information figure 1).
Second, the trend analysis of the three time-series from the Northwest Atlantic (north) revealed an
initial steep decline from 1978 ending in 1995 before recovering steadily to near historical index values.
Overall, the annual rate of increase of 1.7% is consistent with a rapid increase of 1.4% in the most recent
generation and an estimated median increase of 8.5%% over the past three generation lengths (31.8
years) (see Supplementary Information figure 2).
Third, the trend analysis of the North Atlantic (West Greenland) revealed a slight increase with overall
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
4
annual rates of increase of 1.5%, consistent with an estimated median increase of 52.9% over three
generation lengths (31.8 years) (see Supplementary Information figure 3). The shorter east Greenland
survey (2008–2013) was not analysed but exhibits a similar stable trend.
Fourth, the trend analysis of the North Atlantic (Iceland) revealed a steady decline from the mid-1980s
with annual rates of decrease of 1.7%, consistent with an estimated median decrease of 42.8% over
three generation lengths (31.8 years) (see Supplementary Information figure 4).
Fifth, the trend analysis of the Northeast Atlantic (south) in the North Sea revealed a steady increase in
abundance from 1980 until a peak in 1992, thereafter there has been a steady steep decline with annual
rates of decrease of 2.2% consistent with an estimated median decrease of 83.2% over three generation
lengths (31.8 years), with the highest probability of >80% reduction over three generation lengths (see
Supplementary Information figure 5). However, this decline should also be considered in relation to the
longer time-series which indicated an increase in abundance from 1980 until a peak in 1992, with the
current catch-per-unit-effort at similar levels to that observed at the start of the time-series. The recent
elevated abundance in the 1980–1990s is more similar to the early 1900s, while between these periods
Thorny Skate abundance was low (Sguotti et al. 2016). Whilst the reasons for this are uncertain,
multispecies interactions and environmental conditions are potential factors affecting this region.
Sixth, the trend analysis of the Northeast Atlantic (north) in the Barents Sea and Norwegian coast
revealed steady and rapid increase with annual rates of increase of 8.1%, consistent with an estimated
median increase of 226% over three generation lengths (31.8 years), with the highest probability of an
increase over three generation lengths (see Supplementary Information figure 6).
Overall, there is a strong latitudinal pattern in population trends, repeated on both sides of the Atlantic,
with very steep declines (>80% reduction in three generations) in the most southerly parts of this
species' distribution (and Iceland) coupled with recovery and increasing abundance at more northerly
latitudes. The overall weighted trend was calculated by weighting each time-series by an area–based
estimate of the size of each region as a proportion of the species’ global distribution (EOO: extent of
occurrence, see Supplementary Information Table 1). When these trends are taken together, there is a
42% probability that the species is threatened and a 54% probability that it is Least Concern. Overall,
Thorny skate has undergone an estimated population reduction of 30–49% over the last three
generation lengths (31.8–48 years) due the combination of exploitation with habitat shifting and
alteration due to climate change at lower latitudes while, further north, earlier levels of exploitation
that have ceased or greatly decreased. Therefore, Thorny Skate is assessed as Vulnerable A2bcd.
For further information about this species, see Supplementary Material.
Current Population Trend:ÊÊDecreasing
Habitat and Ecology (see Appendix for additional information)
The Thorny Skate is demersal on continental and insular shelves and slopes from nearshore to 1,400 m
depths, usually at 25–440 m (Last et al. 2016). There is regional variation in maximum size, it reaches a
maximum size of 66 cm total length (TL) (North Sea) to 111 cm (NW Atlantic) (Walker 1998, Ebert and
Stehmann 2013). Reproduction is oviparous with fecundity ranging from 10 to 45 egg cases per year
(Templeman 1987), but only 38% of eggs hatching (COSEWIC 2012). Reproduction occurs year round
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
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and size-at-hatch is 10.4–11.4 cm TL (Kulka et al. 2006). Females mature at 38.4–87.3 cm TL and males
mature at 44–83 cm TL (McCully et al. 2012, Lynghammar et al. 2016). Two generation lengths were
used to reflect the striking life history differences between the Northwest Atlantic (south) and
elsewhere. Information on age-at-maturity is available for only two areas, in the North Sea (Northeast
Atlantic) age-at-maturity (Am) is 5.6 years (Walker 1998) and age-at-maturity is 11 years on the Scotian
Shelf (Northwest Atlantic, south) (McPhie and Campana 2009, Simon et al. 2012). From these studies,
generation length is calculated as 10.6 years (North Sea, Northeast Atlantic) and 16 years (Scotian
ShelfNorthwest Atlantic, south), based on GL = Am + 1/M, assuming a natural rate of mortality (M) of
0.2.
Systems:ÊÊMarine
Use and Trade
This skate is used for meat, and the wings are exported to Europe. In the Northeast Atlantic, Thorny
Skate is discarded as it is of limited value due to its smaller size (Ebert and Stehmann 2013).
Threats (see Appendix for additional information)
This skate was taken in target fisheries and as a bycatch mostly in demersal trawl fisheries, with some
catch from gillnet and longline. Most target fisheries have been closed (in Canada) or commercial
retention has been prohibited (in USA), but it is taken as bycatch in trawl fisheries and the majority are
discarded alive in the USA (Sosebee et al. 2016, Sosebee 2019). Discard mortality for Thorny Skate in the
USA bottom trawl fishery is estimated to be low (approximately 16.5–24.5%) (Mandelman et al. 2013,
Knotek et al. 2020). There is a target fishery on the Grand Banks (NAFO Division 3LNOPs) straddling the
200 mile limit and is managed through a total allowable catch (TAC) by the Northwest Atlantic Fisheries
Organisation (NAFO). The TAC has decreased over time but in 2017 continues to exceed the commercial
catch during a period where ‘minimal or no rebuilding of this stock occurred’ (Simpson et al. 2018) but a
population increase can be observed from mid-1990 to 2010, which then levelled off (see
Supplementary Information). In the Barents Sea and Norwegian Sea in the Northeast Atlantic, Thorny
Skate is the greatest fraction of biomass of skates caught in surveys or as bycatch of demersal trawling,
is generally discarded (Dolgov et al. 2005, ICES-WGEF 2018). This species is taken as bycatch in demersal
trawl fisheries in the North Sea (Northeast Atlantic), but it is not targeted and is usually discarded
(Walker and Heessen 1996). The Thorny Skate is a boreo-Arctic species, consequently, some areas of
former habitat have become less suitable as water temperature increases, resulting in northward
distribution shifts and declines in the southern parts of its distributional range, particularly in the North
Sea (Sguotti et al. 2016), and northward shifts have been documented for the Scotian Shelf (Stuart et al.
2020) as well as in the Southern Gulf of St. Lawrence and Newfoundland (Pinsky et al. 2013).
Conservation Actions (see Appendix for additional information)
Commercial retention of this species has been banned since 2003 in the USA, but it is taken as bycatch
in trawl fisheries and the majority are discarded alive (Sosebee et al. 2016, Sosebee 2019). Target
fisheries for mixed skate on the Scotian Shelf were closed in 2002 due to steep declines of Winter Skate
(Leucoraja ocellata) (COSEWIC 2012, 2015). On the Grand Banks, this species is managed under quota
by the Northwest Atlantic Fisheries Organization (NAFO). Spain and Portugal take 90% of quota, which is
currently set at 6,000 tonnes (Simpson et al. 2018). Commercial retention of this species has also been
prohibited in European Union waters of the North Sea and Skagerrak, Northeast Atlantic (EU waters of
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
6
ICES Subarea 4 and Divisions 2.a and 4.a) since 2014.
Credits
Assessor(s): Kulka, D.W., Ellis, J., Anderson, B., Cotton, C.F., Derrick, D., Pacoureau, N. &
Dulvy, N.K.
Reviewer(s): Pollom, R. & Rigby, C.L.
Contributor(s): Bowlby, H., Clark, D., Endicott, M., Fowler, M., Gauthier, J., Jakobsdóttir, B,
Gedamke, T., Knutsen, M., Miri, C., Pasolini, P., Pinsky, L, Regnier-McKellar, C.,
Simpson, M., Sosebee, K., Sulikowski, J., Swain, D., Treble , M. & Winker, H.
Facilitator(s) and
Compiler(s):
Kyne, P.M., Crysler, Z. & Dulvy, N.K.
Authority/Authorities: IUCN SSC Shark Specialist Group (sharks and rays)
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
7
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Citation
Kulka, D.W., Ellis, J., Anderson, B., Cotton, C.F., Derrick, D., Pacoureau, N. & Dulvy, N.K. 2020. Amblyraja
radiata. The IUCN Red List of Threatened Species 2020: e.T161542A124503504.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
9
Disclaimer
To make use of this information, please check the Terms of Use.
External Resources
For Supplementary Material, and for Images and External Links to Additional Information, please see the
Red List website.
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
10
Appendix
Habitats
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Habitat Season Suitability Major
Importance?
9. Marine Neritic -> 9.4. Marine Neritic - Subtidal Sandy Resident Suitable Yes
9. Marine Neritic -> 9.5. Marine Neritic - Subtidal Sandy-Mud Resident Suitable Yes
9. Marine Neritic -> 9.6. Marine Neritic - Subtidal Muddy Resident Suitable Yes
11. Marine Deep Benthic -> 11.1. Marine Deep Benthic - Continental
Slope/Bathyl Zone (200-4,000m)
- - -
Use and Trade
(http://www.iucnredlist.org/technical-documents/classification-schemes)
End Use Local National International
Food - human No Yes Yes
Threats
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Threat Timing Scope Severity Impact Score
5. Biological resource use -> 5.4. Fishing & harvesting
aquatic resources -> 5.4.2. Intentional use: (large
scale) [harvest]
Ongoing Minority (50%) Slow, significant
declines
Low impact: 5
Stresses: 2. Species Stresses -> 2.1. Species mortality
5. Biological resource use -> 5.4. Fishing & harvesting
aquatic resources -> 5.4.4. Unintentional effects:
(large scale) [harvest]
Ongoing Minority (50%) Slow, significant
declines
Low impact: 5
Stresses: 2. Species Stresses -> 2.1. Species mortality
11. Climate change & severe weather -> 11.1. Habitat
shifting & alteration
Ongoing Minority (50%) Slow, significant
declines
Low impact: 5
Stresses: 2. Species Stresses -> 2.2. Species disturbance
Conservation Actions in Place
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Conservation Action in Place
In-place research and monitoring
Action Recovery Plan: No
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
11
Conservation Action in Place
Systematic monitoring scheme: Yes
In-place land/water protection
Conservation sites identified: Yes, over part of range
Area based regional management plan: No
Occurs in at least one protected area: No
Invasive species control or prevention: Not Applicable
In-place species management
Harvest management plan: Yes
Successfully reintroduced or introduced benignly: No
Subject to ex-situ conservation: No
In-place education
Subject to recent education and awareness programmes: No
Included in international legislation: No
Subject to any international management / trade controls: No
Conservation Actions Needed
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Conservation Action Needed
3. Species management -> 3.1. Species management -> 3.1.1. Harvest management
3. Species management -> 3.1. Species management -> 3.1.2. Trade management
5. Law & policy -> 5.1. Legislation -> 5.1.2. National level
Research Needed
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Research Needed
1. Research -> 1.2. Population size, distribution & trends
1. Research -> 1.3. Life history & ecology
2. Conservation Planning -> 2.1. Species Action/Recovery Plan
3. Monitoring -> 3.1. Population trends
3. Monitoring -> 3.2. Harvest level trends
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
12
Additional Data Fields
Distribution
Lower depth limit (m): 1,400
Upper depth limit (m): 0
Habitats and Ecology
Generation Length (years): 16
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
13
The IUCN Red List of Threatened Species™
ISSN 2307-8235 (online)
IUCN 2020: T161542A124503504
Scope(s): Global
Language: English
The IUCN Red List Partnership
The IUCN Red List of Threatened Species™ is produced and managed by the IUCN Global Species
Programme, the IUCN Species Survival Commission (SSC) and The IUCN Red List Partnership.
The IUCN Red List Partners are: Arizona State University; BirdLife International; Botanic Gardens
Conservation International; Conservation International; NatureServe; Royal Botanic Gardens, Kew;
Sapienza University of Rome; Texas A&M University; and Zoological Society of London.
THE IUCN RED LIST OF THREATENED SPECIES™
© The IUCN Red List of Threatened Species: Amblyraja radiata – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161542A124503504.en
14

Supplementary resource (1)

Amblyraja radiata. The IUCN Red List of Threatened Species 2020 - Supplementary.pdf
Data
April 2021
David W Kulka · Jim Ellis · Brooke N Anderson · Charles F Cotton · Nicholas K Dulvy
... The thorny skate (Amblyraja radiata) is a demersal species found on the continental shelf from South Carolina in the Northwest Atlantic (NWA) via Greenland and Iceland to the British Isles and the Barents Sea in the Northeast Atlantic (NEA, Fig. 1) 19 . In the NWA, the thorny skate has long been taken as target catch or bycatch in commercial fisheries. ...
... In the NWA, the thorny skate has long been taken as target catch or bycatch in commercial fisheries. Their abundance has declined steeply in waters off Canada and the US Gulf of Maine over the last 50 years 19,20 . This decline prompted stringent conservation measures that eliminated directed harvest in large geographic areas. ...
... This decline prompted stringent conservation measures that eliminated directed harvest in large geographic areas. However, the Gulf of Maine population has shown no signs of recovery despite two decades of reduced fishing mortality 19,20 . The factors impeding population recovery in the Gulf of Maine remain unknown [21][22][23][24] . ...
Short-term evolutionary implications of an introgressed size-determining supergene in a vulnerable population
Article
Full-text available
  • Jan 2025
The Thorny Skate (Amblyraja radiata) is a vulnerable species displaying a discrete size-polymorphism in the northwest Atlantic Ocean (NWA). We conducted whole genome sequencing of samples collected across its range. Genetic diversity was similar at all sampled sites, but we discovered a ~ 31 megabase bi-allelic supergene associated with the size polymorphism, with the larger size allele having introgressed in the last ~160,000 years B.P. While both Gulf of Maine (GoM) and Canadian (CAN) populations exhibit the size polymorphism, we detected a significant deficit of heterozygotes at the supergene and longer stretches of homozygosity in GoM population. This suggests inbreeding driven by assortative mating for size in GoM but not in CAN. Coalescent-based demographic modelling reveals strong migration between regions maintaining genetic variability in the recombining genome, preventing speciation between morphs. This study highlights short-term context-dependent evolutionary consequences of a size-determining supergene providing new insights for the management of vulnerable species.
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... increasing abundance at more northerly latitudes (Kulka et al., 2020). ...
... The aim of this study was to sequence entire mitogenomes from A. radiata sampled over a broad geographic range to better assess potential population differentiation and genetic links to life-history variation across the North Atlantic, with a particular emphasis on the Northwest Atlantic region. This region is of heightened management interest due to the severe A. radiata population declines evident from the Gulf of Saint Lawrence south to the Gulf of Maine (Kulka et al., 2020) and the unique coexistence of the large-and small size morphs. Population decline in the US Gulf of Maine and the Canadian Scotian Shelf has already led to fishery closures (COSEWIC, 2012;NEFMC, 2003) and multiple petitions to list A. radiata as endangered under the US Endangered Species Act, the most recent of which argued that individuals in the Northwest Atlantic exist as a distinct population segment. ...
... A. radiata is also an obligate T A B L E 2 Results of one-way hierarchical AMOVA assessing geographic clusters of thorny skate, Amblyraja radiata, within a northwest/ northeast structuring. bottom-dweller that exists almost exclusively in continental shelf waters from 25 to 440 m (Kulka et al., 2020) and to depths up to 1442 m (Jørgensen et al., 2005), which restricts available migration pathways to the continental shelf waters and precludes direct movement between distant regions separated by deep ocean habitats. ...
Mitogenomic evidence of population differentiation of thorny skate, Amblyraja radiata, in the North Atlantic
Article
Full-text available
Management of thorny skate (Amblyraja radiata) in the Northwest Atlantic has posed a conservation dilemma for several decades due to the species' lack of response to strong conservation efforts in the US Gulf of Maine and the Canadian Scotian Shelf, confusion over the relationship between two reproductive size morphs of differing life histories that are sympatric in the Northwest Atlantic, and conflicting data on regional population connectivity throughout the species' broader range. To better assess potential A. radiata regional population differentiation and genetic links to life‐history variation, we analysed complete mitochondrial genome sequences from 527 specimens collected across the species' North Atlantic geographic range, with particular emphasis on the Northwest Atlantic region. A high level of genetic diversity was evident across the North Atlantic, but significant genetic differentiation was identified between specimens inhabiting the Northwest (Gulf of Maine and Newfoundland) and Northeast (Greenland, Iceland, North Sea, and Arctic Circle) Atlantic. In the Northwest Atlantic, significant differentiation between the Gulf of Maine and Newfoundland regions was revealed; however, the overall level of differentiation was very low. No genetic difference was identified between the large and small reproductive morphs. The results of this study advance our understanding of A. radiata population structure in the North Atlantic but do not resolve all the questions confounding our understanding of the species' biology and evolutionary history.
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... Thornback ray (Raja clavata; order: Rajiformes) are widespread in the eastern Atlantic Ocean from Iceland to the west coast of Africa (Ebert & Stehmann, 2013) where they are demersal on mud, sand, and coarse ground substrates. They occur from 10 to 300 m, thought to be most abundant from 10 to 60 m (Ebert & Stehmann, 2013;Ellis, 2016). ...
... For example, fisheries catch data can be used to predict habitat suitability and diversity hotspots to support marine spatial planning (e.g., for deep-sea elasmobranchs off the Azores) (Das et al., 2022). 1.4 | Stock status of R. clavata in the North Sea R. clavata is classified as near-threatened on the IUCN Red List of Threatened Species (Ellis, 2016) and is also of conservation concern to the Regional Seas Convention OSPAR, listed as a threatened and/or declining species (OSPAR, 2010 (ICES, 2020(ICES, , 2021bOSPAR, 2021). ...
... Population ecology, and density hotspot information, is especially important to obtain for R. clavata (near threatened [Ellis, 2016]) as they have faced declines in the past due to direct targeting by fisheries, and vulnerability to being caught as by-catch, driven by their large size (Hunter et al., 2006;Walker & Hilsop, 1998;Wiegand et al., 2011). Their vulnerability to fishing pressure may explain the larger abundances observed in shallow areas compared to deeper, inshore areas, as they may be moving shallower to gain some protection. ...
Population ecology and juvenile density hotspots of thornback ray (Raja clavata) around the Shetland Islands, Scotland
Article
Full-text available
Elasmobranchs are facing global decline, and so there is a pressing need for research into their populations to inform effective conservation and management strategies. Little information exists on the population ecology of skate species around the British Isles, presenting an important knowledge gap that this study aimed to reduce. The population ecology of thornback ray (Raja clavata) around the Shetland Islands, Scotland, was investigated in two habitats: inshore (50–150 m deep) and shallow coastal (20–50 m deep), from 2011 to 2022, and 2017 to 2022, respectively. Using trawl survey data from the annual Shetland Inshore Fish Survey, the size composition of R. clavata catches was compared between shallow and inshore habitats across 157 trawl sets, and 885 individuals, over the years 2017–2022. Catch per unit effort (CPUE) of R. clavata was significantly higher in shallow than that in inshore areas (ANOVA, F = 72.52, df = 1, 5, p < 0.001). Size composition also significantly differed between the two habitats (analysis of similarities, R = 0.96, p = 0.002), with R. clavata being smaller in shallow areas and juveniles (<60 cm) occurring more frequently. Spatial distribution maps confirmed density hotspots of juveniles in shallow habitats, with repeated use of certain locations consistent over time. The results of this study provide the first evidence for R. clavata using shallow areas for potential nurseries in Shetland, which can inform the IUCN's Important Shark and Ray Area process. Furthermore, this study provides important new population ecology information for R. clavata around Shetland, which may have important conservation implications and be valuable for informing species and fisheries stock assessments in this region.
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... The thornback skate, Raja clavata (Linnaeus 1758), is amongst the most common and widespread skates in the northeast Atlantic and Mediterranean Sea (Ellis, 2016). This bottom-dwelling and coastal species can be found from the South of the Arctic Circle (Iceland, Norway) to the east Atlantic coast of south Africa (Stehmann, 1995). ...
... As with all Rajidae species, female thornback skates spawn egg capsules which they bury or attach to the substrate (Maia et al., 2015). Classified globally as "Near Threatened" by the IUCN Red List (Ellis, 2016), the thornback skate is among the most frequently captured skates by commercial fisheries in northwest Europe (Santos et al., 2021). In 2019, the global catch of thornback skate reached 6,874 tonnes, most of them being captured as bycatch of trawls and gillnets (FAO, 2021). ...
... The thornback skate is a common species in European multispecies and multi-gear fisheries, including the small-scale fishing sector (Bañón Díaz et al., 2008;Figueiredo et al., 2020), in partially protected areas (Di Lorenzo et al., 2022). Thornback skates rarely escape trawl nets because of their large size and thorns; this, coupled with the slow growth rate and low fertility of skates, makes overfishing a great threat to their populations (Ellis, 2016). It is important to note that, the conservation status of R. clavata appears to show signs of improvement in recent years, with increased biomass and indications of low exploitation levels in the northeast Atlantic (ICES, 2022). ...
Drivers of the spatial behaviour of the threatened thornback skate (Raja clavata)
Article
Full-text available
  • Jul 2023
  • AQUAT LIVING RESOUR
Fish movements are fundamental to their ecology and survival. Understanding the causes and consequences of the spatial behaviour of fish is of high relevance as it provides critical knowledge for conservation purposes. Skate (Rajidae) populations face an unprecedented global decline due to overfishing. In this study, we used acoustic telemetry to track the movements of nine individuals of the near threatened thornback skate (Raja clavata) around the Cíes Islands, a small marine protected area in the northwest of the Iberian Peninsula. Our results demonstrate the significant impacts of biotic and abiotic drivers on the spatial behaviour of R. clavata. Overall residency inside the study array was low (0.073), differed between sexes (higher for females) and over the course of the year (peaking in summer). The analysis of the direction of the excursions performed by R. clavata individuals revealed high consistency in the exit and entry areas and a strong connectivity with inshore waters connecting with the Ría de Vigo, as compared with offshore waters connecting with the open ocean. Finally, the activity space of R. clavata also varied over the time of the year with a peak in summer. This study provides an important baseline information for understanding the spatial behaviour of R. clavata that can serve as a starting point for planning future conservation actions or studies.
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... Also, R. clavata is identified as "near threatened". They are population trend shows a constant decrease (Ellis 2016;Finucci et al. 2021;Jabado et al. 2021). Also, these cartilaginous fishes have late maturation, slow growth and low fecundity, so ecological significance and vulnerability to environmental pressures (Dulvy et al. 2017). ...
Estimation of Economic Losses in Trammel Nets Fisheries Using the Length–weight Relationship
Article
Full-text available
  • Apr 2024
Trammel nets are used with nearly five days of soaking time to increase the catching efficiency of demersal fish under the control of commercial fishers in the Marmara Sea, Türkiye. The long soaking times can be deteriorate or damage individuals of fish species and economic losses. In this situation, the length and weight of fresh individuals can be measured, but damaged individuals can not be measured in length and weight or both. These losses can be revealed by relating of the length–weight relationship. The current study aimed to determine economic losses by estimating the length–weight relationships of known length and weight of fresh individuals, and by calculating the weight of damaged individuals depending on the length–weight relationships. The catching operations with different soaking times were conducted firstly from December 2020 to December 2021 and secondly from the winter and spring seasons of 2022 in the Marmara Sea, Türkiye. A total of 654 individuals of all species were caught and 185 of them were determined to be damaged. This shows that 30% of those caught were damaged individuals. The total weight of the damaged individuals was calculated to be 91.3 kg. The damaged fish were caught with a total of 2000 m trammel nets and it was determined that they caused an economic loss of 355.3 USD. When we consider the decline and overexploitation of fish stocks, these economic losses and damaged individuals with long soaking times for trammel nets are significant. So, the negative effects of long soaking times on catchable stocks should be evaluated by fisheries managers, and the long soaking times of trammel nets should be regulated for sustainable fisheries.
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... All but one (Cedros Island, Mexico) have been substantially impacted by human activities (Burdon et al. 2017, Burdon and Miller 1992, McDonald and Laacke 1990. In 2013 radiata pine was listed as endangered in its native habitat (Farjon 2013). Almost all planted radiata pine in New Zealand has been derived from the Monterey and Año Nuevo mainland populations, the genetic contribution of the latter disproportionately high in relation to its extent. ...
Lessons from insect and disease impacts on radiata pine ( Pinus radiata D. Don) plantations in New Zealand over the last hundred years
Article
Full-text available
  • Sep 2023
The imp acts of past and potential insect pests and diseases in New Zealand's radiata pine plantations are reviewed. Invariably their impacts have decreased with time or can be easily managed. Despite past biotic impacts. growth rates have increased over the last 100 years. Pitch pine canker (PPC) is perceived as the greatest new threat. PPC's impact in California, Spain, Portugal, South Africa and Chile suggests that in New Zealand it would become a nursery problem. Radiata pine remains the best medium-density softwood for New Zealand although climate change may alter the site limits. While a biotic catastrophe, despite its low probability, remains an important risk, this risk is outweighed by the opportunity costs and risks associated with diversifying into alternative species. A strong biosecurity infrastructure is vital, as is maintaining a broad genetic base from which to breed resistance. Large plantation estates should develop defensive strategies against new biotic invasions.
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Embracing change: Invasive species and novel ecosystems
Article
Full-text available
  • May 2024
  • GAIA
Combining ecological and socio-cultural analysis, we propose embracing the future-oriented concept of novel ecosystems. This perspective offers an alternative to the backwards-looking conservation attitude that uses metaphors of biological invasion, for example. With the case study of species whose range is shifting to include cities, we show that in a world of environmental novelty, effective conservation thinking must supplement narratives of invasive species with those about climate refugee species and novel ecosystems.
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A Size-determining Supergene Hampers a Vulnerable Population Recovery
Preprint
Full-text available
  • Mar 2024
Understanding the relationship between census size, recent demography and genetic diversity is central for effective conservation and management of threatened species. Thorny skate (Amblyraja radiata) biomass in the northwest Atlantic has declined significantly in the past 50 years, prompting strict conservation measures . Curiously, population recovery has not occurred in the Gulf of Maine. We conducted whole genome sequencing of thorny skate samples collected from across its range. Genetic diversity was similar in all sampled locations, but we discovered a ~31 megabase supergene bi-allelic locus associated with a discrete size polymorphism occurring in the northwest Atlantic. Historical demographic modelling reveals that the allele associated with larger size originally introgressed into the ancestral thorny skate population ~160,000 years ago. Off Newfoundland (Canada), where population recovered, supergene genotypes are in Hardy-Weinberg equilibrium. In contrast, the Gulf of Maine population, exhibiting the most acute non-recovery, displays a significant deficit of heterozygotes. This strongly implies sub-regional fitness effects associated with the supergene, hindering recovery efforts in the Gulf of Maine. At the same time, regional migration sustains genetic variability in the recombining genome component, preventing speciation between morphs. This study highlights a rarely considered significance of context-dependent genetic compatibilities in the conservation of threatened populations and reconcile census size trajectory with genetic diversity estimates through accurate evolutionary modelling.
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Biological Parameters and Biomass and Abundance Indices of Two Demersal Species, Turbot (Scophthalmus maximus) and Thornback Ray (Raja clavata), Estimated by a Trawl Survey in Western Black Sea
Article
Full-text available
  • Aug 2023
In this study, we determined the biological characteristics and indices of abundance and biomass of two demersal species, turbot and thornback ray, through a scientific trawl survey of Bulgar-ian Black Sea waters in the autumn of 2020. Turbot is among the most valuable fish species in the Black Sea, and thornback ray is a sensitive cartilaginous species with a significantly declining abundance throughout the Mediterranean region. The stock biomass of turbot was estimated at 1467.6 tons, with a relative abundance of 896,922 individuals, and those of the thornback ray were 1187.9 tons and 519,606 individuals, respectively. Mean turbot abundance, interpolated into 0.5 • latitude/longitude grid cells, ranged between 52 and 120 ind·km −2 , with a mean biomass of 78.26-238.31 kg·km −2 , and for the thornback ray, these indices were within the limits of 0-107 ind·km −2 and 0-219 kg·km −2. The distribution of the different length classes of the two fish species by depth layer was analyzed. Length-weight relationships were estimated based on combined samples of both sexes and separately for female and male individuals, allowing a better understanding of growth patterns. Key Contribution: The autumn 2020 bottom trawl survey revealed the biomass, spatial patterns, and biological traits of two sensitive bottom species in the western Black Sea, turbot and thornback ray. Size structure variability across depth strata was evaluated, as were its effects on fluctuations in abundance and biomass. The growth type variability by sex was also estimated.
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Estimating IUCN Red List population reduction: JARA-A decision-support tool applied to pelagic sharks
Article
Full-text available
  • Nov 2019
The International Union for Conservation of Nature's (IUCN) Red List is the global standard for quantifying extinction risk but assessing population reduction (criterion A) of wide-ranging, long-lived marine taxa remains difficult and controversial. We show how Bayesian state-space models (BSSM), coupled with expert knowledge at IUCN Red List workshops, can combine regional abundance data into indices of global population change. To illustrate our approach, we provide examples of the process to assess four circumglobal sharks with differing temporal and spatial data-deficiency: Blue Shark (Prionace glauca), Shortfin Mako (Isurus oxyrinchus), Dusky Shark (Carcharhinus obscurus), and Great Hammerhead (Sphyrna mokarran). For each species, the BSSM provided global population change estimates over three generation lengths bounded by uncertainty levels in intuitive outputs, enabling informed decisions on the status of each species. Integrating similar analyses into future workshops would help conservation practitioners ensure robust, consistent, and transparent Red List assessments for other long-lived, wide-ranging species.
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JARA: 'Just Another Red list Assessment'
Preprint
Full-text available
  • Jun 2019
Identifying species at risk of extinction is necessary to prioritise conservation efforts. The International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species is the global standard for quantifying extinction risk, with many species categorised on the basis of a reduction in population size. We introduce the Bayesian state-space framework ‘JARA’ (Just Another Red-List Assessment). Designed as decision-support tool, JARA allows both process error and uncertainty to be incorporated into IUCN Red List assessments under criterion A. JARA outputs easy to interpret graphics showing the posterior probability of the population decline displayed against the IUCN Red List categories, and assigns each category an associated probability given process and observation uncertainty. JARA is designed to be easy to use, rapid and widely applicable, so conservation practitioners can apply it to their own count or relative abundance data. We illustrate JARA using three real-world examples: (1) relative abundance indices for two elasmobranchs, Yellowspotted Skate Leucoraja wallacei and Whitespot Smoothhound Mustelus palumbes; (2) a comparison of standardized abundance indices for Atlantic Blue Marlin Makaira nigricans and (3) absolute abundance data for Cape Gannets Morus capensis. Finally, using a simulation experiment, we demonstrate how JARA provides greater accuracy than two approaches commonly used to assigning a Red List Status under criterion A. Tools like JARA can help further standardise Red List evaluations, increasing objectivity and lowering the risk of misclassification. The consequences for global conservation efforts could be substantial.
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Distribution of skates and sharks in the North Sea: 112 years of change
Article
Full-text available
  • Apr 2016
  • GLOBAL CHANGE BIOL
How have North Sea skate and shark assemblages changed since the early 20th century when bottom trawling became widespread, while their environment became increasingly impacted by fishing, climate change, habitat degradation and other anthropogenic pressures? This paper examines long-term changes in the distribution and occurrence of the elasmobranch assemblage of the southern North Sea, based on extensive historical time-series (1902-2013) of fishery-independent survey data. In general, larger species (thornback ray, tope, spurdog) exhibited long-term declines, and the largest (common skate complex) became locally extirpated (as did angelshark). Smaller species increased (spotted and starry ray, lesser-spotted dogfish) as did smooth-hound, likely benefiting from greater resilience to fishing and/or climate change. This indicates a fundamental shift from historical dominance of larger, commercially valuable species to current prevalence of smaller, more productive species often of low commercial value. In recent years, however, some trends have reversed, with the (cold-water associated) starry ray now declining and thornback ray increasing. This shift may be attributed to (1) fishing, including mechanised beam trawling introduced in the 1960s-1970s, and historical target fisheries for elasmobranchs; (2) climate change, currently favouring warm-water above cold-water species; and (3) habitat loss, including potential degradation of coastal and outer estuarine nursery habitats. The same anthropogenic pressures, here documented to have impacted North Sea elasmobranchs over the past century, are likewise impacting shelf seas worldwide, and may increase in the future; therefore, parallel changes in elasmobranch communities in other regions are to be expected. This article is protected by copyright. All rights reserved.
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Marine Taxa Track Local Climate Velocities
Article
Full-text available
  • Sep 2013
  • SCIENCE
Organisms are expected to adapt or move in response to climate change, but observed distribution shifts span a wide range of directions and rates. Explanations often emphasize biological distinctions among species, but general mechanisms have been elusive. We tested an alternative hypothesis: that differences in climate velocity—the rate and direction that climate shifts across the landscape—can explain observed species shifts. We compiled a database of coastal surveys around North America from 1968 to 2011, sampling 128 million individuals across 360 marine taxa. Climate velocity explained the magnitude and direction of shifts in latitude and depth much more effectively than did species characteristics. Our results demonstrate that marine species shift at different rates and directions because they closely track the complex mosaic of local climate velocities.
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Long-term changes in ray populations in the North Sea
Article
Full-text available
  • Dec 1996
Three data sets have been analysed: landing statistics (1903-1993), International Bottom Trawl Surveys (1979-1993), and survey data collected in Dutch coastal waters between 1951 and 1994. Landings of rays and skates have decreased by more than half compared with the post-war level. Starry ray has increased in abundance in the central North Sea between 1970 and 1993. Thornback ray virtually disappeared from the Dutch coastal area in 1958. No significant trend has been observed for the other species. ? 1996 International Council for the Exploration of the Sea
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Differences in Sexual Maturity and Related Characteristics Between Populations of Thorny Skate (Raja radiata) in the Northwest Atlantic
Article
  • Jan 1987
Sexual maturity of the thorny skate (Raja radiata) occurs at relatively small sizes off northern Iceland and West Greenland, off Baffin Island and Labrador, on the Northeast Newfoundland Shelf and in the Gulf of S1. Lawrence, and at considerably larger sizes on the Grand Bank and 81. Pierre Bank. In areas with sexual maturity at a small length, the maximum fish lengths weretypicallysmall, and in areas with sexual maturity only at much greater lengths, the maximum lengths were considerably larger. The largest thorny skate was a 104-cm male from the southern Grand Bank. The lengths at sexual maturity and the maximum lengths for males were greater than those for females. One hermaphrodite was noted. There was a higher maximal number of rows of alar spines in areas with sexual maturity at a larger size. From the great differences between areas in length at sexual maturity, it is concluded that no large-scale migrations of thorny skate occurred between these areas.
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Biomass and abundance of demersal fish stocks off West and East Greenland estimated from the Greenland Institute of Natural resources Shrimp Fish Survey
  • Jan 2019
  • 1988-2013
  • R Nygaard
  • A Nogueira
Nygaard, R. and Nogueira, A. 2019. Biomass and abundance of demersal fish stocks off West and East Greenland estimated from the Greenland Institute of Natural resources Shrimp Fish Survey, 1988-2013.
Essential fish habitat source document: Thorny Skate, Amblyraja radiata, life history and habitat characteristics
  • Jan 2003
  • D B Packer
  • C A Zetlin
  • J J Vitaliano
Packer, D.B., Zetlin, C.A. and Vitaliano, J.J. 2003. Essential fish habitat source document: Thorny Skate, Amblyraja radiata, life history and habitat characteristics. NOAA Technical Memorandum. U.S. Department of Commerce, Massachusetts, USA.
Status of smooth skate (Malacoraja senta) and thorny skate (Amblyraja radiata) in the Maritimes Region. Fisheries and Oceans Canada
  • Jan 2011
  • J E Simon
  • S Rowe
  • A Cook
Simon, J.E., Rowe, S. and Cook, A. 2012. Status of smooth skate (Malacoraja senta) and thorny skate (Amblyraja radiata) in the Maritimes Region. Fisheries and Oceans Canada, Can. Sci. Advis. Sec. Res. Doc. 2011/080: viii + 102 p.