Leatherback Sea Turtle (Dermochelys coriacea) Atlantic population: COSEWIC status appraisal summary 2022

Official title: COSEWIC status appraisal summary on the Leatherback Sea Turtle Dermochelys coriacea Atlantic population in Canada

Endangered

2022

COSEWIC assessment summary

Assessment summary – December 2022

Common name: Leatherback Sea Turtle - Atlantic population

Scientific name: Dermochelys coriacea

Status: Endangered

Reason for designation: The Atlantic population of this large, long-lived marine turtle has declined precipitously, with the number of known nesting females reduced by about 60% in a single generation (30 years) and this number is projected to decline by a further 50% within the next generation. Adult turtles nest on beaches in the Wider Caribbean Region, but a significant proportion migrate in summer to forage on jellyfish in marine waters of Atlantic Canada. This species continues to be threatened by bycatch and entanglement in fishing gear, marine pollution, coastal and offshore resource development, climate change, poaching of eggs, and nesting habitat decline.

Occurrence: Quebec, New Brunswick, Prince Edward Island, Nova Scotia, Newfoundland and Labrador, Atlantic Ocean

Status history: The species was considered a single unit and designated Endangered in April 1981. Status re-examined and confirmed in May 2001. Split into two populations in May 2012. The Atlantic population was designated Endangered in May 2012. Status re-examined and confirmed in December 2022.

COSEWIC status appraisal summary

Leatherback Sea Turtle, Atlantic population

Tortue luth, population de l’Atlantique

Dermochelys coriacea

Range of occurrence in Canada (province/territory/ocean): Quebec, New Brunswick, Prince Edward Island, Nova Scotia, Newfoundland and Labrador, Atlantic Ocean

Evidence (indicate as applicable):

No new evidence supports a change in status. However, three newly modelled scenarios in NMFS and USFWS (2020) all resulted in an estimated overall reduction of about 50% in the number of nesting adult females within less than one generation. As a result, criterion A3 was added to the criteria applied in the last assessment. Sub-criterion 'a’ was excluded because declines were based on indices rather than total population counts. Sub-criteria ‘c’ and ‘e’ were added to acknowledge the decline in quality of habitat (c) and the effects of pollutants (e).

Wildlife species

SAS 6 Change in eligibility, taxonomy or designatable units: No

Explanation: No new evidence is available to support a change.

Range

SAS 7 Change in Extent of Occurrence (EOO): No

SAS 8 Change in Index of Area of Occupancy (IAO): No

SAS 9 Change in number of known or inferred current locations^{Footnote 1}: No

SAS 10 Significant new survey information: Yes

Explanation

Canadian context

The Leatherback Sea Turtle (Atlantic population) is seasonally abundant in temperate shelf and slope waters off eastern Canada. It is broadly distributed on the Scotian Shelf throughout the foraging season (June through October) and is regularly found in the southern Gulf of St. Lawrence in late summer and fall (James et al. 2006). DFO convened a Science Response Process in 2019 (DFO 2020b) as an update to their 2012 Zonal Advisory Process to define important habitat for Leatherback Sea Turtles in Atlantic Canada (DFO 2012). The update, which relied on satellite-tracking data, reflected a larger sample size and a longer-term dataset and is the most recent study of habitat use by Leatherback Sea Turtles in Atlantic Canadian waters. Using telemetry data from 128 individual Leatherback Sea Turtles over a period of 19 years, it confirmed the general distribution of the taxon proposed by James et al. in 2006 and identified two primary areas of important habitat: 1) the southeastern Gulf of St. Lawrence and waters off eastern Cape Breton Island, including Sydney Bight, the Cabot Strait and portions of the Magdalen Shallows, and adjacent portions of the Laurentian Channel, and 2) waters south and east of the Burin Peninsula, including parts of Placentia Bay. Peak occupancy occurs in summer and autumn (DFO 2020b).

Northwestern Atlantic context

The Atlantic Canadian and Pacific Canadian populations of Leatherback Sea Turtle are distinct (COSEWIC 2012). Recent work confirms that these two designatable units meet the criteria for discreteness and evolutionary significance recently outlined by COSEWIC (Appendix F5, Operations and Procedures Manual), including distinguishing heritable markers, natural geographic disjunction, and independent evolutionary trajectory for an evolutionarily significant period. Genetic structure reflects global radiation from a single mtDNA lineage with the most divergent haplotypes indicating separation between Atlantic and Indo-Pacific Ocean populations approximately 170,000 years BP (Duchene et al. 2012). Recent published and unpublished genetic evidence (National Marine Fisheries Service and U.S. Fish and Wildlife Service 2020) supports the existence of seven genetically discrete populations globally, which are congruent with the seven regional management units (RMUs) described by Wallace et al. (2010). These populations are separated by behaviour (males and females return to waters near natal nesting beaches to mate) and physical factors (land masses, oceanographic features, currents).

Leatherback Sea Turtles found in Atlantic Canadian waters are part of the broader northwest Atlantic Ocean (NWA) Leatherback Sea Turtle Regional Management Unit (RMU) (Wallace et al. 2010), which ranges throughout the northern Atlantic from nesting areas in the Wider Caribbean Region, including Latin America and the Guiana Shield, to foraging areas extending from the north into temperate latitudes (Figure 1).

In its 2019 assessment of the NWA RMU, the IUCN includes an estimated area of occupancy (IAO) of 2,000 km² and an estimated extent of occurrence (EOO) of 68,997,470 km² (NWALWG 2018, 2019). Although the method used to calculate the IAO was not specified in the IUCN document, for sea turtles it is typically based on nesting area (for example, Tiwari et al. 2013). There is also specific direction from IUCN for authors preparing reports that outlines how to calculate both IAO and EOO, with the former using a 2x2 grid value (Red List Technical Working Group 2018).

Despite the declining trend in the number of NWA RMU Leatherback Sea Turtles, the IAO seems to have remained stable. The Leatherback Sea Turtle exhibits philopatry to a nesting region rather than a specific beach (Eckert et al. 2012; Stewart et al. 2013). Females can move hundreds of kilometres between nesting sites within a single season (NMFS and USFWS 2020).

Population information

SAS 11 Change in number of mature individuals: Yes

SAS 12 Change in population trend: Yes

SAS 13 Change in severity of population fragmentation: Yes

SAS 14 Change in trend in area and/or quality of habitat: No

SAS 15 Significant new survey information: Yes

Explanation

There is one population of Leatherback Sea Turtle in Atlantic Canadian waters which comprises seasonally foraging adults and sub-adults of both sexes representing all the principal nesting stocks of Leatherback Sea Turtle throughout the western Atlantic (Stewart et al. 2013). Archibald and James (2016) suggest that individuals found seasonally in Atlantic Canada number in the hundreds if not thousands. The population in Atlantic Canada is female-biased (1.86 females: 1 male) (James et al. 2007). All other population estimates are for the entire NWA RMU and consider mature (nesting) females.

Recent region-wide trend analyses of the NWA Leatherback Sea Turtle RMU point to its decline. The first analysis, conducted by the Northwest Atlantic Leatherback Working Group (NWALWG) (NWALWG 2018), gathered nesting data from 17 different countries and territories, representing more than 600,000 observed nests region-wide since 1990. Regional abundance-weighted trends were negative across temporal scenarios and indicated statistically measurable regional-scale declines in nest abundance, particularly since 2008, with an overall decline of 4.2% per year (Figure 2). The NWALWG used these data to inform the 2019 Red List Assessment of the NWA Leatherback Sea Turtle RMU, establishing a “past” population estimate (averaging annual nest counts from 1986 to 1990) and a “present” estimate (averaging annual nest counts from 2013–2017) for all nesting sites with >10 years of data (n=23 sites across 14 countries and territories). These calculations resulted in an approximate 60% decline from past (approximately 58,000 nests per year) to present (approximately 23,000 nests per year) estimates, or a 7.9% decline per year.

The National Marine Fisheries Service, in collaboration with the U.S. Fish and Wildlife Service (2020), conducted a status review of Leatherback Sea Turtle under the Endangered Species Act. This review uses a total index of nesting female abundance for the NWA Leatherback Sea Turtle RMU of 20,659, based on data from 24 nesting aggregations in 10 countries over a three-year interval beginning in 2012 or after. Trend analyses of these data indicated a “significant decline” in nesting and decreased productivity within this subpopulation. The associated Extinction Risk Analysis notes that the Northwest Atlantic population’s “continued persistence [is] in question. Clear and present threats place this [population] at a high risk of extinction” (National Marine Fisheries Service and U.S. Fish and Wildlife Service 2020, p. 117).

It should be noted that estimating population abundance in a marine species is challenging, particularly species like sea turtles that are highly migratory on an oceanic scale. Sea turtles lay their eggs on nesting beaches, where eggs and nests are easily counted. Sea turtle nest counts are commonly used globally as an index of abundance and population trends (as above). NMFS and USFWS (2020) note many caveats when using nest trend data, including (1) adult females only account for a small percentage of the population and trends in nester abundance may not be an index for the remainder of the population; (2) calculations assume a stable age distribution; and (3) time series surveys do not always span one generation, or the multiple generations required to reach a stable age distribution. Studies investigating the biases associated with these traditional metrics suggest that they may produce estimates of adult female abundance significantly higher than reality—in some cases by a factor of approximately 2 (Tucker 2010; Weber et al. 2013; Esteban et al. 2017; Casale and Ceriani 2020; Ceriani et al. 2021).

Threats:

SAS 16 Change in nature and/or severity of threats: Yes

Explanation

The understanding of the nature and severity of threats has deepened since the last COSEWIC (2012) assessment. Bycatch in commercial fisheries, particularly fixed-gear fisheries, remains the primary threat to the Leatherback Sea Turtle in Atlantic Canadian waters (Hamelin et al. 2017; DFO 2020a,b). In fact, bycatch continues to be the primary threat to the NWA RMU, generally occurring throughout its range and affecting juveniles, subadults, and adult turtles (NWALWG 2018; DFO 2020a,b; National Marine Fisheries Service and U.S. Fish and Wildlife Service 2020). As part of their 2018 status assessment, the Northwest Atlantic Leatherback Working Group determined that the high levels of Leatherback Sea Turtle bycatch near key nesting beaches (particularly Trinidad and the Guianas; n=approximately 3,000 turtles per year) is likely the primary driver of the current estimated declines in abundance. Additionally, the Leatherback Sea Turtle faces multiple threats at all life stages (NWALWG 2018; DFO 2020a,b; National Marine Fisheries Service and U.S. Fish and Wildlife Service 2020). The cumulative impact of these threats is large and impacts individual survival and productivity. This is corroborated by Innis et al. (2010), who reported that many individuals are simultaneously exposed to multiple threats.

DFO (2020b) considers additional threats to the Atlantic Canadian population of leatherbacks within Canadian waters in order of magnitude, beginning with bycatch and fisheries as the greatest threat. In order from greatest to least threatening, this is followed by: entanglement in ghost fishing gear; underwater noise; marine pollution (plastics and other debris); marine pollution (oil from large-scale oil spills); marine pollution (contaminants excluding oil); vessel strikes; and climate change (DFO 2020b).

The same document considers the threats Canadian leatherbacks face outside of Canadian waters to be the following (in decreasing order of magnitude): (1) harvesting (legal and illegal); (2) coastal development and beach use (affecting nesting habitat); and (3) artificial light (DFO 2020b).

It is worth noting that the IUCN (NWALWG 2019) ranks Take (direct utilization of turtles or eggs for human use, that is, consumption and commercial products) as a threat of greater magnitude than coastal development for the broader NWA RMU. Although climate change also appears last on the list of threats in the IUCN document (NWALWG 2019), there is growing concern about sea turtles’ capacity to persist in a warming world. For example, projected climate warming, which notably affects egg incubation (that is, warmer temperatures cause female-biased sex ratios and higher embryo mortality), may have sublethal effects across all life stages, ultimately affecting population viability (Maurer et al. 2021).

Protection

SAS 17 Change in effective protection: No

Explanation

No change since last assessment.

Rescue effect:

SAS 18 Change in evidence of rescue effect: No

Explanation

No change since last assessment. Only the Southwest Atlantic Ocean population (Critically Endangered – IUCN 2022) and Southeast Atlantic Ocean population (Data Deficient – IUCN 2022) have the potential to provide immigrants.

Quantitative analysis:

SAS 19 Change in estimated probability of extirpation: Yes

Explanation

Because significant study of the Leatherback Sea Turtle population in Atlantic Canada has only occurred over the last approximately 20 years, the most recent available data on abundance and threats (Archibald and James 2016; Hamelin et al. 2017; DFO 2020b) do not compare how these factors have changed over time. However, because the seasonally resident population in Atlantic Canadian waters is part of the broader NWA RMU, the sharp decline in the nesting population described in SAS 11–14 is relevant here (NWALWG 2018; DFO 2020a, b; National Marine Fisheries Service and U.S. Fish and Wildlife Service 2020), particularly the Extinction Risk Analysis in the National Marine Fisheries Service and U.S. Fish and Wildlife Service (2020) document cited above.

Summary and additional considerations [for example, recovery efforts; summarize exactly what has changed since the previous assessment]

Research and conservation activities related to the Leatherback Sea Turtle in Atlantic Canada have continued in earnest since the 2012 COSEWIC assessment. These efforts have largely been guided by both the Atlantic Leatherback Recovery Strategy (Atlantic Leatherback Turtle Recovery Team 2006) and the Atlantic Leatherback Action Plan (DFO 2020a). Efforts have focused on identifying and understanding anthropogenic threats in Atlantic Canadian waters; understanding life history characteristics through research and monitoring; identifying important habitat in Atlantic Canada; minimizing harm from anthropogenic activities under Canadian jurisdiction, particularly commercial fishing activities; developing and implementing educational programming for commercial fishermen, coastal communities, and other Canadians; and promoting international initiatives that contribute to Leatherback Sea Turtle recovery in the Atlantic. (See Table 1 of the Action Plan for the Leatherback Sea Turtle, Atlantic Population(DFO 2020a) for details on the status of individual activities. See DFO 2022 for an update on the progress of Recovery Strategy implementation from 2013 to 2019.)

Key findings since the 2012 COSEWIC assessment include knowledge that Atlantic Canadian waters host an annual, seasonal foraging population of adults and sub-adults of both sexes representing all the principal nesting stocks of the Leatherback Sea Turtle throughout the western Atlantic (Stewart et al. 2013; Archibald and James 2016). In addition, off Atlantic Canada, a Leatherback Sea Turtle can consume conservatively more than 200 kg (more than 220 jellyfish per day) or approximately 50% of its body mass in gelatinous zooplankton daily (Wallace et al. 2018). This means a single foraging season (off Atlantic Canada) could support 59% of a non-breeding Leatherback Sea Turtle’s annual energy budget and 29% of the energetic requirements for a female on a two-year breeding cycle (Wallace et al. 2018). The concomitant importance of conserving Leatherback Sea Turtles in Atlantic Canadian waters is evident (Wallace et al. 2018).

The most notable change to our understanding of population dynamics is the recently quantified long-term negative trend in annual nest abundance described in more detail in SAS 11-16 of the Status Appraisal Summary.

Acknowledgements

Thanks are extended to Dr. Michael James, Emily Bond, and Kelly Hall of the Sea Turtle Unit at Fisheries and Oceans Canada, and also to Lei Harris, Katherine Hastings, Koren Spence at DFO, and to their colleagues at the Species at Risk Management Division. Thank you to the fishermen and citizen scientists who volunteer with the Canadian Sea Turtle Network, to the members of the Atlantic Leatherback Turtle Recovery Team and to the committed, incredible work of the international sea turtle community, with special thanks to Dr. Bryan Wallace and Dr. Karen Eckert.

Authorities contacted

• Dr. Karen Eckert, Executive Director, Wider Caribbean Sea Turtle Conservation Network (WIDECAST) and Principia College, 6116 High Meadow Drive, Godfrey, Illinois 62035 USA
• Dr. Michael James, Biologist, Fisheries and Oceans Canada, St. Andrews Biological Station, 125 Marine Science Drive, St. Andrews, NB E5B 0E4
• Dr. Bryan Wallace, Ecolibrium and Adjunct Assistant Professor, University of Colorado, Boulder, CO 80309-0334

Information sources

Archibald, D.W., and M.C. James. 2016. Evaluating inter-annual relative abundance of leatherback sea turtles in Atlantic Canada. Marine Ecology Progress Series 547:233-246. https://DOI:10.3354/meps11648.

Atlantic Leatherback Turtle Recovery Team 2006. Recovery Strategy for Leatherback Turtle (Dermochelys coriacea) in Atlantic Canada. Species at Risk Act Recovery Strategy Series. Fisheries and Oceans Canada, Ottawa, vi + 45 pp.

Avens, L., L.R. Goshe, G.R. Zug, G.H. Balazs, S.R. Benson, and H. Harris. 2020. Regional comparison of leatherback sea turtle maturation attributes and reproductive longevity. Marine Biology 167:4.

Avens, L., J.C. Taylor, L.R. Goshe, T.T. Jones, and M. Hastings. 2009. Use of skeletochronological analysis to estimate the age of leatherback sea turtles (Dermochelys coriacea) in the western North Atlantic. Endangered Species Research 8:165-177.

Casale, P., and S. A. Ceriani. 2020. Sea turtle populations are overestimated worldwide from remigration intervals: correction for bias. Endangered Species Research 41:141-151. https://doi.org/10.3354/esr01019.

Ceriani, S.A., B. Brost, A.B. Meylan, P.A. Meylan, and P. Casale. 2021. Bias in sea turtle productivity estimates: error and factors involved. Marine Biology 168, Article number: 41.

COSEWIC. 2001. COSEWIC assessment and update status report on the leatherback turtle Dermochelys coriacea in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 25 pp.

COSEWIC. 2012. COSEWIC assessment and status report on the Leatherback Sea Turtle Dermochelys coriacea in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xv + 58 pp. (https://species-registry.canada.ca/index-en.html#/documents/2461

Eckert, K.L., B.P. Wallace, J.G. Frazier, S.A. Eckert, and P.C.H. Pritchard. 2012. Synopsis of the biological data on the leatherback sea turtle (Dermochelys coriacea). U.S. Department of Interior; Fish and Wildlife Service, Biological Technical Publication BTP-R4015-2012, Washington, D.C.

Esteban, N., J.A. Mortimer, and G.C. Hayes. 2017. How numbers of nesting sea turtles can be overestimated by nearly a factor of two. Proceedings of the Royal Society B 284: 20162581. http://dx.doi.org/10.1098/rspb.2016.2581.

Fisheries and Oceans Canada (DFO). 2012. Using Satellite Tracking Data to Define Important Habitat for Leatherback Turtles in Atlantic Canada. Fisheries and Oceans Canada. Canadian Science Advisory Secretariat Science Advisory Report 2012/036.

Fisheries and Oceans Canada (DFO). 2019. Using Satellite Tracking Data to Define Important Habitat for Leatherback Turtles in Atlantic Canada: 2019 Update. Fisheries and Oceans Canada. Canadian Science Advisory Secretariat Science Advisory Report 2020/041.

Fisheries and Oceans Canada (DFO). 2020a. Action Plan for the Leatherback Sea Turtle (Dermochelys coriacea), Atlantic population, in Canada. Species at Risk Act Action Plan Series. Fisheries and Oceans Canada, Ottawa. iv + 28 p.

Fisheries and Oceans Canada (DFO). 2020b. Threat Assessment for Leatherback Sea Turtle (Dermochelys coriacea), Northwest Atlantic Subpopulation. Fisheries and Oceans Canada. Canadian Science Advisory Secretariat Science Advisory Response 2020/039.

Fisheries and Oceans Canada (DFO). 2022. Report on the Progress of Recovery Strategy Implementation for the Leatherback Sea Turtle (Dermochelys coriacea) in Atlantic Canada for the Period 2013 to 2019. Species at Risk Act Recovery Strategy Report Series. Fisheries and Oceans Canada, Ottawa. iv + 42 pp.

Hamelin, K.M., M.C. James, W. Ledwell, J. Huntington, and K. Martin. 2017. Incidental capture of leatherback sea turtles in fixed fishing gear off Atlantic Canada. Aquatic Conservation: Marine and Freshwater Ecosystems 1-12. https://onlinelibrary.wiley.com/doi/full/10.1002/aqc.2733.

Innis C., C. Merigo, K. Dodge, M. Tlusty, M. Dodge, B. Sharp, A. Myers, A. Mcintosh, D. Wunn, C. Perkins, T.H. Herdt, T. Norton, and M. Lutcavage. 2010. Health evaluation of leatherback turtles (Dermochelys coriacea) in the northwestern Atlantic during direct capture and fisheries gear disentanglement. Chelonian Conservation and Biology 9:205- 222.

IUCN 2022. The IUCN Red List of Threatened Species. Version 2022-2. https://www.iucnredlist.org.

James, M.C. 2001. Update COSEWIC status report on the leatherback turtle Dermochelys coriacea in Canada, in COSEWIC assessment and update status report on the leatherback turtle Dermochelys coriacea in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 1-25 pp.

James, M.C., S.A. Sherrill-Mix, K. Martin, and R.A. Myers. 2006. Canadian waters provide critical foraging habitat for leatherback turtles. Biological Conservation 133:347-357. https://doi.org/10.1016/j.biocon.2006.06.012.

James, M.C., S.A. Sherrill-Mix, and R.A. Myers. 2007. Population characteristics and seasonal migrations of leatherback sea turtles at high latitudes. Marine Ecology Progress Series 337:245-254.

Maurer, A.S., J.A. Seminoff, C.A. Layman, S.P. Stapleton, M.H. Godfrey, and M.O. Burford Reiskind. 2021. Population viability of sea turtles in the context of global warming. BioScience 71:790-804. https://doi.org/10.1093/biosci/biab028.

National Marine Fisheries Service and U.S. Fish and Wildlife Service. 2020. Endangered Species Act status review of the leatherback turtle (Dermochelys coriacea). Report to the National Marine Fisheries Service Office of Protected Resources and U.S. Fish and Wildlife Service.

Northwest Atlantic Leatherback Working Group. 2018. Northwest Atlantic Leatherback Turtle (Dermochelys coriacea) Status Assessment (Bryan Wallace and Karen Eckert, Compilers and Editors). Conservation Science Partners and the Wider Caribbean Sea Turtle Conservation Network (WIDECAST). WIDECAST Technical Report No. 16. Godfrey, Illinois. 36 pp.

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Red List Technical Working Group. 2018. Mapping Standards and Data Quality for the IUCN Red List Categories and Criteria, Version 1.16, 30 pp.

Stewart, K.R., M.C. James, S. Roden, and P.H. Dutton. 2013. Assignment tests, telemetry and tag-recapture data converge to identify natal origins of leatherback turtles foraging in Atlantic Canadian waters. Journal of Animal Ecology 82:791-603. https://doi.org/10.1111/1365-2656.12056.

Tiwari, M., B.P. Wallace, and M. Girondot. 2013. Dermochelys coriacea (West Pacific Ocean subpopulation). The IUCN Red List of Threatened Species 2013: e.T46967817A46967821.

Tucker, A.D. 2010. Nest site fidelity and clutch frequency of loggerhead turtles are better elucidated by satellite telemetry than by nocturnal tagging efforts: Implications for stock estimation. Journal of Experimental Marine Biology and Ecology 383:48-55. https://doi.org/10.1016/j.jembe.2009.11.009

Wallace, B.P., A.D., DiMatteo, B.J. Hurley, E.M. Finkbeiner, A.B. Bolten, M.Y. Chaloupka, B.J. Hutchinson, F.A. Abreu-Grobois, D. Amorocho, K.A. Bjorndal, J. Bourjea, B.W. Bowen, R. Briseño-Dueñas, P. Casales, B.C. Choudhury, A. Costa, P.H. Dutton, A. Fallabrino, A. Girard, M. Girondot, M.H. Godfrey, M. Hamann, M. López-Mendilaharsu, M.A. Marcovaldi, J.A. Mortimer, J.A. Musick, R. Nel, N.J. Pilcher, J.A. Seminoff, S. Troëng, B. Witherington, and R.B. Mast. 2010. Regional management units for marine turtles: A novel framework for prioritizing conservation and research across multiple scales. PLoS ONE 5(12): e15465. https://doi.org/10.1371/journal.pone.0015465.

Wallace, B.P., and T.T. Jones. 2015. Leatherback turtle physiological ecology. J.R. Spotila and M.S. Tomillo, Eds. The leatherback turtle: biology and conservation. Baltimore, MD: Johns Hopkins Press. pp. 149-161.

Wallace, B.P., M. Zolkewitz, and M.C. James. 2018. Discrete, high-latitude foraging areas are important to energy budgets and population dynamics of migratory leatherback turtles. Scientific Reports 8:11017. https://www.nature.com/articles/s41598-018-29106-1.

Weber, N., S.B. Weber, B.J. Godley, J. Ellick, M. Witt, and A.C. Broderick. 2013. Telemetry as a tool for improving estimates of marine turtle abundance. Biological Conservation 167:90-96.

Writer of status appraisal summary:

• Kathleen Martin, Canadian Sea Turtle Network

Figure 1. Distribution of NWA Leatherback Sea Turtle RMU. Source: Wallace et al. 2010.

Figure 2. Regional-level trends in Leatherback Sea Turtle Northwest Atlantic Ocean population for 1990–2017. Line is geometric annual mean trend, weighted by relative site-level abundance, across a total of 23 sites in Suriname, French Guiana, Guyana, Trinidad and Tobago, Grenada, Venezuela, Costa Rica, Panama, Colombia, St. Croix, Puerto Rico, St. Kitts, Guadeloupe, British Virgin Islands, and Florida; shaded area is 95% credible intervals (Trend: -4.2%/yr; 95% CIs: -6.7%/yr to -2.2%/yr). Trends estimated using Bayesian regression analysis approach. Figure adapted from NWALWG 2018 and 2019.

Technical summary

Dermochelys coriacea

Leatherback Sea Turtle, Atlantic population

Tortue luth, population de l’Atlantique

Range of occurrence in Canada (province/territory/ocean): Quebec, New Brunswick, Prince Edward Island, Nova Scotia, Newfoundland and Labrador, Atlantic Ocean

[Note: As specific Canadian information is not available, data used here are based on the northwest Atlantic Ocean Leatherback Sea Turtle Regional Management Unit, which is inclusive of all Canadian Leatherback Sea Turtles in the Atlantic.]

Demographic information

Generation time (usually average age of parents in the population; indicate if another method of estimating generation time indicated in the IUCN guidelines (2011) is being used).

Few age and growth data have been reported for Leatherback Turtle and estimates range widely (Avens et al. 2009; Wallace and Jones 2015). Generation time used here is based on that used by IUCN (NWALWG 2018), NMFS and USFWS (2020), and the work of Avens et al. (2020).

Approximately 30 years

Is there an [observed, inferred, or projected] continuing decline in number of mature individuals?

See SAS 11-15

Yes, estimated, inferred and projected

Estimated percent of continuing decline in total number of mature individuals within [5 years or 2 generations, whichever is longer up to a maximum of 100 years].

See SAS 11, 12 and 15. This projection based on NMFS and USFWS (2020), which tested three scenarios to determine how long it would take for nester abundance to be reduced by 50%. All scenarios resulted in a 50% nester reduction in less than one generation (8 to 17 years to decline by 50%). Trend analyses by NWALWG (2018, 2019) did not include projections.

Inferred 50% reduction in abundance of mature nesting females in less than one generation (approximately 30 years)

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last [10 years, or 3 generations, whichever is longer up to a maximum of 100 years].

See SAS 11, 12 and 15. This projection based on NMFS and USFWS (2020), which tested three scenarios to determine how long it would take for nester abundance to be reduced by 50%. All scenarios resulted in a 50% nester reduction in less than one generation (8 to 17 years to decline by 50%). Trend analyses by NWALWG (2018, 2019) did not include projections

Inferred 50% reduction in abundance of mature nesting females in less than one generation (approximately 30 years)

[Projected or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations, whichever is longer up to a maximum of 100 years].

See SAS 11, 12 and 15. This projection based on NMFS and USFWS (2020), which tested three scenarios to determine how long it would take for nester abundance to be reduced by 50%. All scenarios resulted in a 50% nester reduction in less than one generation (8 to 17 years to decline by 50%). Trend analyses by NWALWG (2018, 2019) did not include projections.

Projected 50% reduction in abundance of mature nesting females in less than one generation (approximately 30 years). Decline at a similarly high rate into the future is suspected..

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over any period [10 years, or 3 generations, whichever is longer up to a maximum of 100 years], including both the past and the future.

As per #3-5 above, sufficient data do not exist to assess 3 generations of this population (NWALWG 2018, 2019; NMFS and USFWS 2020).

Inferred and projected reduction of much greater than 50%, based on past declines of nesting females over one generation and continuing threats, particularly bycatch.

Are the causes of the decline a. clearly reversible and b. understood and c. ceased?

See SAS 16

a) partially reversible, b) partially understood, and c) not ceased.

Are there extreme fluctuations in number of mature individuals?

No

Extent and occupancy information

Estimated extent of occurrence (EOO).

As determined for the NWA Leatherback Sea Turtle RMU throughout its range by NWALWG (2019) for the IUCN Assessment

68,997,470 km² (global range including Canadian)

Index of area of occupancy (IAO) (Always report 2x2 grid value).

See SAS 8.

2,000 km² (based on nesting sites)

Is the population severely fragmented i.e., is >50% of its total area of occupancy in habitat patches that are (a) smaller than would be required to support a viable population, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?

1. No
2. No

Number of locations (use plausible range to reflect uncertainty if appropriate)*.

1-10 (based on international bycatch)

Is there an [observed, inferred, or projected] decline in extent of occurrence?

No

Is there an [observed, inferred, or projected] decline in index of area of occupancy?

No

Is there an [observed, inferred, or projected] decline in number of subpopulations?

No

Is there an [observed, inferred, or projected] decline in number of locations*?

No

Is there an [observed, inferred, or projected] decline in [area, extent and/or quality] of habitat?

This is detailed in the threats analyses included in DFO 2020b; NWALWG 2018, 2019; and NMFS and USFWS 2020. Particularly noteworthy are threats to nesting beach habitat. See also SAS 16.

Yes, observed, inferred and projected decline in area and quality of habitat.

Are there extreme fluctuations in number of subpopulations?

No

Are there extreme fluctuations in number of locations*?

No

Are there extreme fluctuations in extent of occurrence?

No

Are there extreme fluctuations in index of area of occupancy?

No

* See COSEWIC definitions and abbreviations on website for more information on this term.

Number of mature individuals (in each subpopulation)

Subpopulations (give plausible ranges) total: One population in Atlantic Canadian waters consisting of individuals from several nesting sites (Stewart et al. 2013). Archibald and James (2016) suggest that leatherbacks found seasonally in Atlantic Canada number in the hundreds if not thousands. Population in Atlantic Canada is female-biased (1.86 females: 1 male) (James et al. 2007). All other population estimates are for the entire NWA RMU and consider mature (nesting) females. These range from 20,659 (NMFS and USFWS 2020) to approximately 23,000 (NWALWG 2019). Data on number of adult males in the NWA Leatherback Sea Turtle RMU are not available. Note: See SAS 15 re: accuracy of estimates.

N Mature Individuals total: 20,659 to approximately 23,000 nesting females.

Quantitative analysis

Is the probability of extinction in the wild at least [20% within 20 years or 5 generations whichever is longer up to a maximum of 100 years, or 10% within 100 years]?

Projection of 50% reduction in abundance of mature nesting females in less than one generation, based on NMFS and USFWS (2020), but probability of extinction not calculated. See SAS 11, 12, and 15 and notes on #3 above for details

Analysis not conducted.

Threats (direct, from highest impact to least, as per IUCN threats calculator)

Was a threats calculator completed for this species?

No.

See SAS 16. No independent threats calculator was completed; however, IUCN (2019) assessed threats to the NWA RMU, and DFO (2020b) to the Atlantic Canadian (AC) population as well as NWA RMU (NWA) of Leatherback Sea Turtle. Threats compiled by DFO (2020b) include:

1. Fisheries bycatch – High (NWA), Low (AC)
2. Entanglement in ghost fishing gear – Low (NWA), Unknown (AC)
3. Marine pollution: plastics and other debris – Med (NWA), Low (AC)
4. Marine pollution: oil (large-scale oil spills) – Low (NWA, Low (AC)
5. Marine pollution: contaminants (excluding oil) – Low (NWA), Unknown (AC)
6. Vessel strikes – Low (NWA), Unknown (AC)
7. Climate change – Low (NWA), Unknown (AC)

Additional threats - NWA only:

1. Harvesting (legal and illegal) – Medium (NWA)
2. Coastal development and beach use – Medium (NWA)
3. Artificial light – Low (NWA)

What additional limiting factors are relevant?

Late maturation and long generation time limit resilience to population perturbations, and long-distance migrations increase exposure to fisheries bycatch risk and pollution.

Rescue effect (immigration from outside Canada)

Status of outside population(s) most likely to provide immigrants to Canada.

Canadian turtles are part of the wider ranging Northwest Atlantic population. The Southeast Atlantic population (data deficient - IUCN 2022) and Southwest Atlantic population (Critically Endangered – IUCN 2022) are the only potential source of immigrants.

Endangered

Is immigration known or possible?

Possible

Would immigrants be adapted to survive in Canada?

Yes

Is there sufficient habitat for immigrants in Canada?

Yes

Are conditions deteriorating in Canada?⁺

See SAS 19. Because significant study of this population in the Canadian context has only occurred over the last approximately 20 years, the most recent available data on threats (Archibald and James 2016; Hamelin et al. 2017; DFO 2020b) do not compare how these have changed over time.

Unknown in Canadian waters, but deteriorating on nesting beaches and migration routes

Are conditions for the source (that is, outside) population deteriorating?⁺

See SAS 14 and 16.

Yes

Is the Canadian population considered to be a sink?⁺

No

Is rescue from outside populations likely?

No

Data sensitive species

Is this a data sensitive species?

No

⁺ See Table 3 (Guidelines for modifying status assessment based on rescue effect).

Status history

COSEWIC status history

The species was considered a single unit and designated Endangered in April 1981. Status re-examined and confirmed in May 2001. Split into two populations in May 2012. The Atlantic population was designated Endangered in May 2012. Status re-examined and confirmed in December 2022.

Status and reasons for designation

Status: Endangered

Alpha-numeric codes: A2bcde+3bcde+4bcde

Reasons for designation: The Atlantic population of this large, long-lived marine turtle has declined precipitously, with the number of known nesting females reduced by about 60% in a single generation (30 years) and this number is projected to decline by a further 50% within the next generation. Adult turtles nest on beaches in the Wider Caribbean Region, but a significant proportion migrate in summer to forage on jellyfish in marine waters of Atlantic Canada. This species continues to be threatened by bycatch and entanglement in fishing gear, marine pollution, coastal and offshore resource development, climate change, poaching of eggs, and nesting habitat decline.

Applicability of criteria

Criterion A (Decline in total number of mature individuals): Meets Endangered, A2bcde+3bcde+4bcde. Observed approximate 60% decline in total number of mature individuals in one generation; Projected 50% reduction in abundance of mature nesting females in less than one generation; Inferred reduction of much greater than 50%, based on past declines of nesting females and continuing threats, particularly harvesting and bycatch.

Criterion B (Small distribution range and decline or fluctuation): May meet Threatened, B2ab(iii,v). IAO < or = 2,000 km²; population may occur at < or = 10 locations, and there is an observed, inferred and projected decline in habitat.

Criterion C (Small and declining number of mature individuals): Not applicable. Number of mature individuals exceeds the threshold for Threatened.

Criterion D (Very small or restricted population): Not applicable. The population is neither very small nor restricted.

Criterion E (Quantitative analysis): Not applicable. Analysis not conducted.

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2022)

Wildlife Species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)**

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)***

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.

** Formerly described as “Not In Any Category”, or “No Designation Required.”

*** Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.