Greenland Shark (Somniosus microcephalus): COSEWIC assessment and status report 2025

Official title: COSEWIC assessment and status report on the Greenland Shark (Somniosus microcephalus) in Canada

Special Concern

2025

COSEWIC assessment summary

Assessment summary – May 2025

Common name: Greenland Shark

Scientific name: Somniosus microcephalus

Status: Special Concern

Reason for designation: This large, highly-mobile shark inhabits primarily northern waters throughout the Atlantic and Arctic oceans. It is caught incidentally in trawl, benthic longline, and gillnet fisheries, with estimates of at least 1700 sharks bycaught annually in Canada. The remarkably slow growth, late maturity (approximately 150 years), and longevity, make it vulnerable to overfishing. This species inhabits regions experiencing accelerated climate change, which may impact its distribution, fitness, and population dynamics.

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

Status history: Designated Special Concern in May 2025.

COSEWIC executive summary

Greenland Shark

Somniosus microcephalus

Wildlife species description and significance

Greenland Shark (Somniosus microcephalus) is a large sleeper shark species from the family Somniosidae, known to inhabit polar waters. This species can be distinguished from other sharks by the presence of two small, relatively equal-sized, spineless dorsal fins, with the first dorsal originating near the mid-body, and no anal fin. Greenland Shark is the largest fish in Arctic waters and is currently believed to be among the longest-living vertebrates.

Aboriginal (Indigenous) knowledge

Aboriginal Traditional Knowledge (ATK) is relationship-based. It involves information on ecological relationships between humans and their environment, including characteristics of species, habitats, and locations. Laws and protocols for human relationships with the environment are passed on through teachings and stories, and Indigenous languages, and can be based on long-term observations. Place names provide information about harvesting areas, ecological processes, spiritual significance or the products of harvest. ATK can identify life history characteristics of a species or distinct differences between similar species. All species are significant and are interconnected and interrelated. ATK has been included under the relevant headings of the report.

Distribution

Greenland Shark is found primarily throughout the North Atlantic Ocean and adjacent Arctic waters. It occurs in the deep waters of the Gulf of Mexico and the Caribbean, extending northward along the eastern U.S. and throughout Atlantic Canada and the eastern Canadian Arctic. It is also present across Greenland and Iceland, and further east from France, extending north throughout the Northeast Atlantic to Svalbard and as far east as northern Russia. In Canada, a seasonally higher abundance of Greenland Shark has been observed in inshore fjords of Nunavut in the summer months.

Habitat

Greenland Shark inhabits a variety of both inshore and offshore habitats, from coastal fjords and brackish estuarine waters to oceanic regions along continental shelves and slopes. Bathymetric range is from surface waters to a depth of at least 2,900 m, but individuals spend significant time off the seafloor at mesopelagic depths. Greenland Shark can tolerate a wide range of temperatures from -1.8°C to 17.2°C, but appear to prefer cooler temperatures from 0°C to 5°C. In the Canadian Arctic, at least some sharks appear to occupy cold inshore waters more frequently during summer months and warmer waters offshore during winter and spring. It is uncertain whether ontogenetic shifts in habitat use occur, as sharks of all sizes have been observed both inshore and offshore throughout their range.

Biology

Although there is high uncertainty with current age estimates, Greenland Shark may be among the longest-living vertebrate species, with one study suggesting the lifespan of the largest individual to be 392 years (± 120 years based on the extent of 95.4% probability range) and estimated the age at sexual maturity to be 156 years (± 22 years based on the extent of 95.4% probability range). These estimates have yet to be validated, as no viable alternative method currently exists, and uncertainties in radiocarbon dynamics in the deep ocean, both before and after nuclear weapons testing, result in high uncertainty in determining birth dates. Reproductive potential, litter size, gestation period, and length of reproductive cycle are uncertain, as are mating sites and pupping grounds. Total body length at maturity (TL₅₀) is estimated to be 284 ± 6 cm for males and 419 ± 4 cm for females. Generation time has been estimated to range from 63 to greater than 200 years (y), but is likely between 150 and 200 y based on current estimates of age-at-maturity and longevity, with maximum intrinsic population growth rates ranging from 0.024 to 0.064, with a median value of 0.032.

Population sizes and trends

There are currently no estimates of Greenland Shark population size in Canadian waters. A recent attempt to estimate global abundance, based on population reconstruction models using historical landings data, current catch data and bycatch estimates, suggests a potential decline over the last three generations. However, estimated declines range widely, anywhere between 1% and 100%, due to the high uncertainty in both life history parameters (for example, age, fecundity, gestation rate) and mortality estimates, resulting in high uncertainty in calculations of generation time and population growth rates. Therefore, population size and trends in abundance are considered unknown.

Threats

Anthropogenic activities are the most significant threat to Greenland Shark. Greenland Shark is reported as incidental bycatch in a wide variety of trawl, demersal longline, and gillnet fisheries throughout its range, with global estimates of at least 3,500 sharks bycaught in fisheries each year, and is the target of directed artisanal, small-scale fisheries in Iceland and Greenland. Bycatch in Canadian fisheries is estimated to range from at least 1,688 to 2,208 sharks annually. The extreme life history traits of the species, including remarkably slow growth, late maturity, and longevity, makes it particularly high-risk to overfishing. Given that Greenland Shark primarily inhabits regions experiencing climate change impacts at an accelerated rate (two to four times faster in the Arctic compared with the global average), the species may experience changes to habitat (for example, extent of sea ice coverage) that could impact its distribution, fitness, and population dynamics in Canada.

Protection, status, and recovery activities

Greenland Shark was globally designated as Vulnerable under criteria A2bd by the IUCN (International Union for Conservation of Nature) in 2020, an uplisting from Near Threatened in 2006. In Canada, the Fisheries (General) Regulations and licence conditions for groundfish prohibit the retention of Greenland Shark, and individuals must be released alive with as little harm as possible. In 2022, the Northwest Atlantic Fisheries Organization (NAFO) agreed to a ban on Greenland Shark retention for all fisheries occurring within NAFO Regulatory Areas. Although most sharks are released, post-release survivorship of discarded Greenland Shark bycatch is largely unknown.

Technical summary

Somniosus microcephalus

Greenland Shark

Laimarque atlantique^{Footnote 1} (preferred), Laimargue de l’atlantique^{Footnote 2}, Requin du Groenland, Iqalukjuaq

Range of occurrence in Canada: Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador, Nunavut, Arctic Ocean, Atlantic Ocean

Demographic information

Generation time (usually average age of parents in the population)

Uncertain

Kulka et al. (2020) propose generation time may range from 63 to greater than 200 y, due to high uncertainty in age and mortality estimates, but use 150 y as most likely value for population reconstruction.

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

Probable

Kulka et al. (2020) inferred global declines between 11% and 72% based on population reconstruction trajectories over three generations, but uncertainty in life history and mortality parameters resulted in a range of decline estimates from 1% to 100%.

[Observed, estimated, or projected] percent of continuing decline in total number of mature individuals within 3 years [or 1 generation; whichever is longer up to a maximum of 100 years]

Uncertain

Kulka et al. (2020) suggested a potential 3% global increase over the past 100 y based on population reconstructions. However, high uncertainty and assumptions in parameters yielded estimates ranging from a 57% increase to a 100% decline.

Observed, estimated, or projected] 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]

Uncertain

Kulka et al. (2020) suggested a potential 3% global increase over the past 100 y based on population reconstructions. However, high uncertainty and assumptions in parameters yielded estimates ranging from a 57% increase to a 100% decline.

[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]

Uncertain

Kulka et al. (2020) inferred global declines of 59%, but ranging between 11% and 72% based on population reconstruction trajectories over three generations. However, uncertainty in life history and mortality parameters resulted in decline estimates ranging from 9% to 100% depending on assumed generation length.

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

Unknown

Unknown overall threats impact.

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

Unknown

Unknown

Are the causes of the decline clearly reversible?

Unknown

Fishing-related mortalities appear to be the largest threat to Greenland Shark. Reducing bycatch rates and fishing mortalities could potentially reverse any declines the population has incurred. Potential for declines from other sources, such as changes in ocean climate conditions, are unknown.

Are the causes of the decline clearly understood?

No

Presumed declines to date, whether by 1% or 100%, are attributed to overfishing, historically through directed fishing for liver oil. Since the 1960s, this species has also been caught as incidental bycatch in a wide variety of fisheries. Some information on survival of released bycatch is available, but estimates are dependent on fishing and handling practices. Potential for declines from other sources, such as changes in ocean climate conditions, are not understood.

Are the causes of the decline clearly ceased?

Unknown, potentially not

Significant reduction in the number of sharks caught by historic targeted fisheries. Current bycatch rates are poorly estimated due to lack of observer coverage, poor bycatch reporting, and knowledge of fishing and handling practices.

Are there extreme fluctuations in number of mature individuals

No

Extent and occupancy information

Estimated extent of occurrence (EOO)

Extent of Occurrence (EOO) of 6,998,103 km²

Calculated based on minimum convex polygon around known occurrences 1983 to 2023.

Index of area of occupancy (IAO), reported as 2 × 2 km grid value

Index of Area of Occupancy (IAO) of 1,806 km²

Discontinuous IAO calculated from all fishery-independent research surveys including visual surveys (2005 to 2023) and from occurrence records by Indigenous harvesters.

Is the population “severely fragmented,” that is, is >50% of individuals or >50% of the total area “occupied” (as a proxy for number of individuals) in habitat patches that are both (a) smaller than required to support a viable subpopulation, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?

No

No

Greenland Shark has a broad geographic range and occupies a wide range of connected habitats. It is capable of long-distance movements and dispersal between regions with no known risk of fragmentation.

Number of “locations” (use plausible range to reflect uncertainty if appropriate)

One

Based on ubiquitous threat of fishing-related mortality throughout its range and high mobility.

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

Unknown

Unknown, potential increase due to warming Arctic waters and declining sea ice.

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

No

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

Not applicable

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

No

Single location

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

Unknown

A movement study by Edwards et al. (2022) suggests some sharks may coordinate movements with sea ice extent; therefore, inferred climate effects on sea ice distribution and timing may affect foraging and/or migratory behaviour.

Are there extreme fluctuations in number of subpopulations?

Not applicable

Are there extreme fluctuations in number of “locations”?

No

Are there extreme fluctuations in extent of occurrence?

Unlikely

Are there extreme fluctuations in index of area of occupancy?

Unlikely

Number of mature individuals (by subpopulation)

Total

Unknown

There are currently no estimates of the total number of mature individuals.

Quantitative analysis

Is the probability of extinction in the wild at least 20% within 20 years [or 5 generations], or 10% within 100 years]

Unknown

Analysis not undertaken.

Threats:

Was a threats calculator completed for this species?

Yes, on 14/01/25 (see Appendix 1)

Overall assigned threat impact: Unknown (multiple recognized threats with Unknown impact).

Key threats were identified as:

5.4 Fishing and harvesting aquatic resources – Unknown, Potentially High

Bycatch in fisheries (IUCN 5.4.4) – Unknown (Pervasive/Unknown/High)

11.0 Climate change and severe weather – Unknown (Pervasive/Unknown/High)

11.1 (Habitat shifting and alteration), 11.3 (Temperature extremes) – Both Pervasive/Unknown/High

What limiting factors are relevant?

Slow intrinsic population growth rate.

Rescue effect (from outside Canada)

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

Unknown

Abundance of Greenland Shark within and outside of Canadian waters is unknown, but currently presumed to be a single population with connectivity between regions outside of Canadian waters.

Is immigration known or possible?

Yes

Tracking studies indicate Greenland Shark frequently travel long distances, with connectivity between broader regions outside of Canadian waters.

Would immigrants be adapted to survive in Canada?

Yes

Canada represents a portion of available habitat for Greenland Shark and offers similar conditions to areas outside of Canada. Further, the species displays a strong tolerance for a wide range of depths and temperatures.

Is there sufficient habitat for immigrants in Canada?

Yes

Are conditions deteriorating in Canada?

Unknown

Much of Greenland Shark range occurs in the Arctic, where the impacts of global climate change are occurring at a rapid rate; however, it is uncertain how these changes may impact the species.

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

Unknown

Much of Greenland Shark range occurs in the Arctic, where the impacts of global climate change are occurring at a rapid rate; however, it is uncertain how these changes may impact the species.

Is the Canadian population considered to be a sink?

Unknown

It is unknown whether reproduction occurs in Canadian waters: many Greenland Sharks observed in the Canadian Arctic appear to be immature juveniles (Hussey et al. 2014; Devine et al. 2018) although larger, potentially mature individuals have been observed in Atlantic Canada. No pups or neonates have been reported in Canadian waters.

Is rescue from outside Canada likely, such that it could lead to a change in status?

No, under current DU understanding

Based on current knowledge, Greenland Shark in Canada is part of a single North Atlantic Designatable Unit (DU), thus sharks from outside Canada cannot contribute to rescue of the population in Canada. In addition, global population reconstructions suggest Greenland Shark abundance is in decline to some degree, and given that Greenland Shark outside of Canada are subjected to similar if not higher threat impacts, it is uncertain whether immigration would be sufficient to offset extirpation in Canada.

Wildlife species with sensitive occurrence data (general caution for consideration)

Could release of certain occurrence data result in increased harm to the Wildlife Species or its habitat?

No

Current status

COSEWIC status: Not applicable

Year of previous assessment: Not previously assessed

COSEWIC status history: Not applicable

Criteria: Not applicable

Reasons for designation: Not applicable

Status and reasons for designation

Status: Special Concern (b,c)

Alpha-numeric codes: Not applicable

Reason for change in status: Not applicable

Reasons for designation: This large, highly-mobile shark inhabits primarily northern waters throughout the Atlantic and Arctic oceans. It is caught incidentally in trawl, benthic longline, and gillnet fisheries, with estimates of at least 1700 sharks bycaught annually in Canada. The remarkably slow growth, late maturity (approximately 150 years), and longevity, make it vulnerable to overfishing. This species inhabits regions experiencing accelerated climate change, which may impact its distribution, fitness, and population dynamics.

Applicability of criteria

A: Decline in total number of mature individuals

Applicability Statement

Not applicable. May meet Endangered or Threatened, A2b. Inferred 9.8 to 100% decline in number of mature individuals over the past three generations, but based on highly uncertain population reconstruction.

B: Small range and decline or fluctuation

Applicability Statement

Not applicable. IAO (1,806 km²) is below the threshold for Threatened, but population is not severely fragmented. There is no evidence of a continuing decline, and extreme fluctuations are not experienced.

C: Small and declining number of mature individuals

Applicability Statement

Not applicable. Number of mature individuals is unknown, but believed to exceed thresholds.

D: Very small or restricted population

Applicability Statement

Not applicable. Number of mature individuals is unknown, but believed to exceed thresholds.

E: Quantitative analysis

Applicability Statement

Not applicable; analysis not conducted.

Special concern:

(b) the Wildlife Species may become Threatened if factors suspected of negatively influencing the persistence of the Wildlife Species are neither reversed nor managed with demonstrable effectiveness; and

(c) the Wildlife Species is near to qualifying, under any criterion, for Threatened status

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

(2025)

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.

Wildlife species description and significance

Name and classification

Current classification

Class: Elasmobranchii

Order: Squaliformes

Family: Somniosidae

Genus: Somniosus

Species: Somniosus microcephalus

Subspecies in Canada: None

Common names

English: Greenland Shark, ground shark, grey shark, sleeper shark, gurry shark (Fishbase)

French: Laimargue atlantique, requin du Groenland, requin dormeur, requin de fond, requin de glace, requin du nord (Fishbase ; DFO ; St. Lawrence Shark Observatory)

Indigenous (specify language): Iqalukjuaq; Ekalugssuak; Ekalugssup piara; Eqalugssuaq; Eqaluksuaq; Eqalukuak; Eqalusuaq; Iqalugjuaq; Iqalujjuaq; Iqalukuak (Inuktitut/Nunavut); Iqalutjuaq (Inuktitut/Nunavik); Iqalugyuaq (Inuinnaqtun) (Nunavut Coastal Resource Inventory)

Greenland Shark (Somniosus microcephalus) is one of 17 species of sleeper sharks belonging to the family Somniosidae (order Squaliformes). Etymology; Somniosus (Lesueur 1818), Latin for “sleepy,” attributing to their slow, sluggish behaviour; microcephalus (Bloch and Schneider, 1801), from mik-ros (small) and cephalus (headed), unknown allusion, but possibly due to the relatively short, rounded snout compared with other sharks. Synonyms for this species as listed in the Catalog of Fishes (California Academy of Sciences) are Squalus borealis (Scoresby 1820), Somniosus brevipinna (Lesueur, 1818), Leiodon echinatum (Wood, 1846), Scymnus glacialis (Faber, 1829), Scymnus gunneri (Thienemann, 1828), Squalus microcephalus (Bloch and Schneider, 1801), Scymnus micropterus (Valenciennes, 1832), and Squalus norvegianus (Blainville, 1825). The genus Somniosus is considered to contain six species and is organized into two subgenera: Rhinoscymnus and Somniosus (Yano et al. 2004). Greenland Shark is one of three species currently placed within Somniosus (Somniosus), which contains the largest representatives of the family (>200 cm) and further differs from Somniosus (Rhinoscymnus) by having more tooth rows on the lower jaw and hook-like dermal denticles (Yano et al. 2004).

Description of wildlife species

Greenland Shark is distinguished from other sharks by the presence of two small, relatively equal-sized, spineless dorsal fins, with the first dorsal originating near the mid-body, and no anal fin (Figure 1). The mouth is relatively small, with slender thorn-like teeth on the upper jaw and broad strongly oblique-cusped teeth on the lower jaw (Figure 2). The body is heavy and cylindrical, with a rounded snout. Eyes are relatively small and often occluded by the ectoparasitic copepod Ommatokoita elongata. The first dorsal fin originates well posterior to the pectoral fin base and the second dorsal fin originates near the pelvic fin insertion. The pectoral fins originate immediately behind the last gill slit, and are small and rounded. The caudal fin is asymmetrical with a short dorsal lobe, having a small but noticeable subterminal notch. Lateral keels are present in the caudal area. Colour is variable, ranging from greyish-brown to blackish with dark or pale spots (Mecklenburg et al. 2002; Coad and Reist 2018).

Figure 1. Greenland Shark (Somniosus microcephalus). (Drawing by Brynn Devine)

Figure 2. Greenland Shark dentition of the upper and lower jaws.

Greenland Shark is among the largest shark species in Canada and is the largest fish known to inhabit Arctic waters. Sexual dimorphism in size is present: males are smaller, reaching total lengths (TL) up to 375 cm compared with larger females which may attain sizes up to 550 cm TL (Nielsen et al. 2020). Common lengths are between 200 and 400 cm TL (Compagno 1984). Sizes can vary among regions, with smaller Greenland Shark observed in the Canadian Arctic compared with specimens observed in other parts of their range (Hussey et al. 2015; Devine et al. 2018).

Somniosus microcephalus is morphologically similar to the two other large somniosids in the subgenus Somniosus: Pacific Sleeper Shark (Somniosus pacificus) known primarily from the North Pacific Ocean, and Southern Sleeper Shark (Somniosus antarcticus) in southern oceans and Antarctic waters (Figure 3). To date, there is no taxonomic character identified that can be used to unequivocally distinguish species within Somniosus (Somniosus). Yano et al. (2004) suggested that several morphometric characters distinguish these species, including interdorsal space and prebranchial length; however, these traits are highly variable and with considerable overlap in characters among these species. Benz et al. (2007) suggest that Yano et al.’s (2004) analyses may conflate interspecific and intraspecific variation by grouping sharks by geography. They also suggest that genetic analyses may be necessary for species identification. Recent genetic analyses have questioned Somniosus subgenus classifications based on morphology and geography, given evidence of hybridization within the group (Hussey et al. 2015; Walter et al. 2017). Although genetic data support S. microcephalus and S. pacificus as distinct but closely related sister species (Murray et al. 2008; Walter et al. 2017), several studies suggest there is insufficient genetic variation to distinguish S. pacificus from S. antarcticus and thus do not support S. antarcticus as a separate species (Murray et al. 2008; Christensen 2022; Timm et al. 2022).

Figure 3. Map of global Greenland Shark distribution. Source: AquaMaps, FishBase

Designatable units

The population structure of Greenland Shark is not well known; however, there are no known subspecies or barriers to migration or dispersal that might produce a discrete unit. No designatable units (DU) have been described for Greenland Shark in Canada.

Current COSEWIC guidelines consider two criteria for both discreteness and evolutionary significance, requiring at least one criterion from each category to be met in order for a DU to be recognized.

Discreteness

D1. Evidence of DU-wide heritable (culturally or genetically) traits or markers that clearly distinguish the possible DU from other DUs (for example, evidence from genetic markers or heritable morphology, behaviour, life history, phenology, migration routes, vocal dialects).

• High-quality examination of whole mitochondrial genome of Greenland Shark across the Atlantic indicates mitogenome variation of Greenland Shark is high, with nearly all sampled individuals across sampled areas possessing unique haplotypes. Greenland Shark appears to form three major mitochondrial clades in the Atlantic that are not related to geography, but rather reflect their extreme longevity (Præbel pers. comm. 2023). There is no evidence of heritable morphology, behaviour, or life history traits that clearly distinguish Greenland Shark between broader regions

D2. Natural (that is, not the product of human disturbance) geographic disjunction between possible DUs such that transmission of information (for example, individuals, seeds, gametes) between these “range portions” has been limited for sufficient time that discrete units are likely to have arisen (for example, via genetic or cultural drift) as defined in D1.

• There is no evidence of natural geographic disjunction for an extended time throughout the Greenland Shark range and it is not likely in the foreseeable future. Tagging studies show Greenland Shark is capable of long-distance movements, and connectivity exists between broader regions within Canada and adjacent waters (Campana et al. 2015; Hussey et al. 2018; Edwards et al. 2022)

Evolutionary significance

S1. Direct evidence or strong inference that the possible DU has been on an evolutionary trajectory long enough to generate an evolutionary history not found elsewhere in Canada. Such evidence might include phylogenetic data indicating origins in DU-specific Pleistocene refugia.

S2. Direct evidence or strong inference that the possible DU possesses DU-wide (heritable) adaptive traits not found elsewhere in Canada. Evidence might include the persistence of the possible DU in an ecological setting where a selective regime is likely to have given rise to DU-wide local adaptations not found elsewhere.

• There is no evidence of any independent evolutionary trajectory within an evolutionary significant period for Greenland Shark, nor is there evidence this species contains putative DUs within discrete ecological settings that harbour adaptive and/or heritable traits that could not be reconstituted if lost

Neither Discreteness nor Evolutionary Significance criteria are met. Therefore, for the purpose of this report, Greenland Shark in Canada is considered a single designatable unit (DU).

Special significance

A significant portion of Greenland Shark distribution lies within Canadian waters, including potential nursery areas evidenced by the presence of juvenile sharks (Hussey et al. 2015; Devine et al. 2018). Greenland Shark is the largest fish in Arctic waters and one of only a few polar shark species. As both a top predator and scavenger, it may play an important ecological role in Arctic marine ecosystems. Given notable life history traits, including slow growth, late maturation, and potential lifespans exceeding 200 y (Nielsen et al. 2016), overfishing may pose a particularly high risk to Greenland Shark.

Aboriginal (Indigenous) knowledge

Aboriginal and Traditional Knowledge (ATK) is relationship-based. It involves information on ecological relationships between humans and their environment, including characteristics of species, habitats, and locations. Laws and protocols for human relationships with the environment are passed on through teachings and stories, and Indigenous languages, and can be based on long-term observations. Place names provide information about harvesting areas, ecological processes, spiritual significance or the products of harvest. ATK can identify life history characteristics of a species or distinct differences between similar species.

Cultural significance to Indigenous Peoples

Greenland Shark has a broad distribution throughout much of northeastern Canada, coincident with Indigenous Peoples in this region. However, limited ATK is publicly available for this species. Reports from published literature combined with 128 observations within the Nunavut Coastal Resource Inventory (NCRI) indicate shark presence in waters adjacent to at least 20 communities (Figure 4; NCRI 2024; Cardinal pers. comm.), although additional efforts to engage with other communities would undoubtedly yield more observations of this widespread species. Notes on behaviour within the NCRI observations often indicated shark presence during marine mammal harvesting, observed feeding on Beluga (Delphinapterus leucas) carcasses, or as a bycatch in gillnets. The most extensive information comes from Nunavut regions where deep-water fishing for Greenland Halibut (Reinhardtius hippoglossoides) occurs, in which the sharks are encountered as bycatch. Information on cultural importance indicates no social or economic benefits derived from the species, and it is therefore not known to be of cultural significance to Indigenous Peoples in Canada. Interviews with Pangnirtung Inuit (Qikiqtaaluk region) did not reveal any stories about Greenland Sharks, but rather similar to other regions, the species is commonly viewed as a “nuisance” given its proclivity for fishing gear entanglement/damage, and the knowledge that sharks prey on harvested species such as Greenland Halibut and seals (Idrobo 2008; Idrobo and Berkes 2012). ATK has been included under the relevant headings of the report; information sources are indicated.

Figure 4. Communities reporting observations of Greenland Shark in local waters of the Canadian Arctic. Observations reported from interviews within the Nunavut Coastal Resource Inventory database (NCRI 2024).

Distribution

Global range

Greenland Shark is known primarily to the North Atlantic Ocean and adjacent Arctic waters (Figure 3). In the North Atlantic, the species is found from the northeastern U.S. and throughout Atlantic Canada, across to Greenland, Iceland, the Faroe Islands, and Norway. Occasional sightings have been recorded as far south as France, Spain, and along the Mid-Atlantic Ridge to 42° N latitude. In Arctic waters, it is known throughout the Eastern Canadian Arctic, Greenland, Svalbard, Franz Josef Land, and the Barents Sea (Rusyaev et al. 2010), as well as the White and Kara seas (Borodavkina et al. 2019). Additional records of Somniosus sp. from underwater video in the western Atlantic have occurred in Georgia, U.S. (Herdendorf and Berra 1995), Cuba (Moreno and Pol 1992), the Gulf of Mexico (Benz et al. 2007), and in the Caribbean Sea (Acero et al. 2017); however, the considerable overlap among identification traits of large somniosids prevents unequivocal identification as S. microcephalus. Given evidence of introgressive hybridization with S. pacificus in both the Gulf of Mexico and Canadian Arctic (Walter et al. 2017), and the confirmed presence of S. pacificus in the North Atlantic (Walter et al. 2017; Kim Præbel pers. comm.), definitive identification as S. microcephalus and not hybrids or S. pacificus requires genetic confirmation, particularly for rare occurrences outside of the core distribution. Adult sharks were found to occur more often north of 73° N and smaller sharks encountered more in the southwestern region of the Barents Sea (Rusyaev et al. 2010). In the Northwest Atlantic, large females are uncommon far north but occur primarily in the offshore area around 62° N in West Greenland (Hedeholm et al. 2018).

Canadian range

Greenland Sharks have been observed from the Scotian Shelf, Gulf of St. Lawrence and St. Lawrence Estuary (including the Saguenay River), extending north around the Grand Banks and Flemish Cap, Labrador Sea, Baffin Bay, and north to at least Smith Sound, located between Ellesmere Island and northwest Greenland (Figure 4). They are found beyond the eastern extent of Canadian waters and westward throughout Hudson Strait, with reports of shark sightings in Igloolik within the Northwestern Passages, in Hudson Bay from Ivujivik, and in Kuujjuarapik in northern Quebec. Further north-westward extensions within the Canadian Arctic Archipelago are known to at least Qausuittuq (Resolute) with additional Greenland Shark observations reported from Iqaluktuuttiaq (Cambridge Bay), Nunavut. Reports of “large sharks” observed in Paulatuk, Northwest Territories were not confirmed as Greenland Shark (KAVIK-AXYS 2012): the eastern extent of S. pacificus in these areas is unknown. This species occurs in biogeographic zones 1 to 3 (COSEWIC O&P Appendix F5, 2023; Figure 2.).

The distribution of Greenland Shark, particularly in deep, offshore waters, has largely been inferred from observed bycatch in Canadian fisheries (Figure 5), but with relatively limited sampling in deep water, the actual distribution may be greater. Additional observations outside of commercial fishing footprints have come from scientific fishing, for example, dive observations and sampling (Harvey-Clark et al. 2005; Gallant et al. 2016), baited camera surveys (Devine et al. 2018), exploratory fishing (Young 2009, 2010; Wheeland and Devine 2018), and ATK of shark sightings by northern communities (for example, NCRI 2024) (Figure 4). These records have provided insight into the distribution of Greenland Shark in inshore waters and potential higher abundance in fjords and inlets of Nunavut during summer months (Young 2009, 2010; Devine et al. 2018). Its extent into regions not inhabited or fished, such as within isolated interior waterways of the High Arctic and the Central Arctic Ocean, is unknown.

Figure 5. Greenland Shark bycatch reported by At-Sea Observers, DFO surveys, and Greenland logbooks combined and spanning 1983 to 2019, with lines and labels indicating North Atlantic Fisheries Organization (NAFO) Divisions (Simpson et al. 2021).

Population structure

The population structure of Greenland Shark is not well known. Recent research has characterized 13 novel microsatellite markers for S. microcephalus (Swintek and Walter 2021). Detailed examination of the mitochondrial genome of Greenland Shark sampled across the Atlantic (Canada, Greenland, Svalbard, and Norway) found remarkably high mitogenome variation, with nearly all individuals possessing unique haplotypes. Greenland Shark appears to form three major mitochondrial clades in the Atlantic that is not related to geography (Præbel pers. comm. 2023).

Extent of occurrence and area of occupancy

The data for estimating the Extent of Occurrence (EOO) and Index Area of Occupancy (IAO) included capture records held by DFO from all fishery sectors (1983–present), fishery-independent research surveys including visual surveys (2005–present), and occurrence records by Indigenous harvesters (NCRI 2024). EOO and IAO are calculated by the COSEWIC Secretariat.

The method for estimating EOO and IAO included land in order to be consistent with COSEWIC (2020) and International Union for Conservation of Nature (IUCN) (IUCN Standards and Petitions Subcommittee 2017) criteria guidelines. EOO is measured by drawing the smallest minimum convex polygon (that is, no internal angle exceeds 180 degrees) that contains all occurrences. IAO is measured as the surface area of 2 × 2 km grid cells that intersect the actual area of recorded occurrence of Greenland Shark (that is, the biological area of occupancy). This is a discontinuous measurement of IAO.

Using these approaches, the EOO for Greenland Shark was 6,998,103 km², with an IAO of 1,806 km² based on 452 grid cells (Figure 6).

Figure 6. Estimated Extent of Occurrence (EOO) and Index of Area of Occupancy (IAO) for Greenland Shark in Canadian Atlantic Ocean waters.

Fluctuations and trends in distribution

As Greenland Shark distribution is largely known from fishery-dependent data sources, there are few data available to detect changes in distribution over time. Observations of localized declines in bycatch abundance following periods of high fishing mortality have been reported (Hansen 1963; Young 2010). More research is needed on shark movements to better understand annual and potential interannual migratory behaviours among regions and differentiate whether these observed local declines arise through changes in distribution or abundance. The only noted potential change in distribution and/or abundance comes from the St. Lawrence Estuary. Greenland Shark was regularly observed by divers at an annual study site in Baie-Comeau from 2003 to 2012; however, the numbers started to decline around 2008. Only a single shark was observed in 2012 and there have been no observations since, despite a similar level and timing of diving effort in the region and occasional shark sightings elsewhere within the St. Lawrence Estuary (Gallant pers. comm. 2023).

Biology and habitat use

Life cycle and reproduction

Age and growth of Greenland Shark is not well known, but limited data suggest remarkably slow growth, late maturation, and longevity. Annual growth has been estimated to be ≤1 cm based on few mark-recapture individuals in West Greenland (size range 262 to 300 cm; Hansen 1963). Due to lack of spines and poor calcification of vertebrae, traditional elasmobranch aging methods are not possible. A single aging study has been conducted to date, using radiocarbon isotopes taken from eye lens nuclei to estimate age for 28 female sharks ranging in size from 81 to 502 cm TL, captured in waters off Greenland (Nielsen et al. 2016). The results of this study suggested the lifespan of the largest individual to be 392 years (± 120 years based on the extent of 95.4% probability range) and estimated the age at sexual maturity to be 156 years (± 22 years based on the extent of 95.4% probability range). It should be noted these estimates have yet to be validated as no viable alternative method currently exists, and uncertainty of radiocarbon dynamics in the deep ocean, both before and after nuclear weapons testing, results in high uncertainty in birth dates (Kulka et al. 2020). Yano et al. (2007) first estimated Greenland shark size-at-maturity to be 450 cm for females and 300 cm for males based on examination of gonad morphology in relation to total length in 49 specimens (n = 34 females, n = 15 males). A recent study by Nielsen et al. (2020) provides a more comprehensive reproductive examination of 312 specimens sampled from Greenland, Svalbard, and Norway, estimating total body length at maturity (TL₅₀) to be 419 ± 4 cm for females and 284 ± 6 cm for males (Figure 7).

Figure 7. Fitted maturity curves for male and female sharks (Nielsen et al. 2020). TL is total length.

Reproduction occurs through lecithotrophic viviparity. High ovarian fecundity (number of unfertilized, ripe ova) has been observed in adult females over 400 cm TL, carrying over 500 ova, approximately 7 to 8 cm in diameter when ripe (Figure 8; Nielsen et al. 2014, 2020; Carter and Soma 2020). An anecdotal report of large eggs present in females between February to June, with only smaller eggs present after this time (Bjerkan 1957), has yet to be validated. Uterine fecundity (number of fertilized ova / developing pups in the uterus) or litter size is uncertain. Only two observations of females carrying pups exist: 1) a report of a Greenland Shark caught in late August offshore of the Faroe Islands, with 10 pups with no external yolks found in the right uterus, suggesting the embryos were near full term (approximately 37 cm length for the single pup examined; Koefoed 1957); and 2) a report of a gravid female with a single fetus approximately 98 cm in length caught in January in Norway (Bjerkan 1957). It has been noted that species identification was not verified in this second observation, with the suggestion that this single large pup could have been from a Basking Shark (Cetorhinus maximus), a species that has often been misidentified as Greenland Shark and known to have fewer, larger pups (Nielsen et al. 2020). There are also limited observations of pregnant females in other somniosids for comparison, but these report a range of litter sizes: 8 to 9 pups in S. rostratus (Cigala Fulgosi and Gandolfi 1983; Barrull and Mate 2001), 10 to 14 pups in Portuguese Dogfish (Centroscymnus coelolepis) (Verissimo et al. 2003; Figueiredo et al. 2008), 33 pups in Taiwan Sleeper Shark (S. cheni) (newly described species based on morphology, lacking genetic data; Hsu et al. 2020), and 8 to 12 pups in S. pacificus (Matta et al. 2024).

While Nielsen et al. (2020) support the estimated 35 to 45 cm size-at-birth reported by Koefoed (1957), the authors speculate a potential uterine fecundity of 200 to 324 pups per pregnancy based on meta-analysis of ovarian vs. uterine fecundity in 23 other species of squaliform sharks. They also suggest the potential for capture-induced abortion of near-term fetuses as a likely explanation for the low uterine fecundity observed in previous reports of litter sizes for somniosids mentioned above; a behaviour that has been observed in a range of live-bearing elasmobranch species (Adams et al. 2018). A subsequent study examining comparative energetics across chondrichthyans species suggests likely resorption of most eggs and estimates that a mean clutch size of 250 eggs would correspond to a theoretical maximum litter size of approximately 22 pups for a 5 m shark (Augustine et al. 2022). Future observations of gravid Greenland Sharks are needed to verify fecundity estimates, which currently could be as low as 10 pups or as high as 200 to 324 pups. Gestation time is unknown, but for other Squaliforms can be 1 to 2 years (Nielsen et al. 2020) and theoretical estimates based on energetics suggest potentially upwards of 4.7 years (Augustine et al. 2022). Localities of mating and pupping grounds are also unknown. Nearly all reproductive biology research has occurred from samples in Greenland, and it is unknown if traits vary among regions.

Figure 8. Image of a dissected Greenland Shark with ripe/ripening ova (above) and close-up of large ova (below) (Nielsen et al. 2020).

Given uncertainty in age, fecundity, and gestation rate, there is high uncertainty in calculations of generation time, mortality rates, and population growth rates. The only published attempt to produce these estimates calculated a range of rates based on different generation time scenarios (range 50 to 250 y), resulting in maximum intrinsic population growth rate estimates ranging from 0.024 to 0.064, with a median value of 0.032 (Kulka et al. 2020). However, this study assumed biennial reproduction, fecundity between 1 and 3 pups per litter, and natural mortality as 1/generation length, which are all parameters with high uncertainty and not aligned with estimates from the literature.

Habitat requirements

Greenland Shark occurs in both inshore and offshore waters, from coastal continental and insular shelves to deep slope habitats. Although typically considered a deep-water species, Greenland Shark occupies a wide range of depths from 0 m down to at least 2,900 m (Porteiro et al. 2017). Individuals have been observed swimming at the surface over deep-water (Borodavkina et al. 2019) and occasionally in very shallow coastal water when drawn toward the shoreline by the presence of whale offal (Hansen 1963; LeClerc et al. 2011). It is commonly found in northern fjords throughout its range, even to the innermost reaches of fjord basins (MacNeil et al. 2012). It is also known to inhabit brackish, temperate waters of the St. Lawrence Estuary and Saguenay River (Stokesbury et al. 2005; Gallant et al. 2016).

Acoustic transmitter and pop-up satellite archival transmitting (PSAT) tag tracking research has revealed Greenland Sharks spend significant time in the pelagic environment and should not be considered a purely benthic species (Skomal and Benz 2004; Stokesbury et al. 2005; Fisk et al. 2012; Campana et al. 2015). It is challenging to surmise where individuals are within the water column and relative to the seafloor from satellite tag data, as light-level and geolocation data between tagging and pop-up locations are largely unavailable for this deep-dwelling species. However, relatively shallow (<500 m) depths recorded by tags over deep, offshore waters and the wide range of depths occupied daily through frequent oscillatory swimming marked by abrupt excursions to depths greater than 900 m provide strong evidence for pelagic swimming by tagged sharks (Figure 9; Fisk et al. 2012; Campana et al. 2015). Depth use may vary with latitude, with sharks further north occupying shallower depths (Yano et al. 2007). Campana et al. (2015) report tagged Greenland Sharks in the Canadian Arctic occupy a shallower and more limited depth range than sharks tagged off Newfoundland in the Northwest Atlantic. Observations nearer the tropics show sharks occurring at depths beyond 2,000 m (Herdendorf and Berra 1995; Benz et al. 2007).

Greenland Sharks can tolerate a wide range of temperatures from -1.8°C to 17.2°C (Campana et al. 2015), but appear more commonly at cooler temperatures, with a majority of records occurring at temperatures under 5°C (MacNeil et al. 2012). In the Barents Sea, water temperature has been considered an important factor related to shark abundance, demonstrated by higher numbers in cooler years (Rusyaev et al. 2010). Monthly depth and temperature data from sharks tagged in the Canadian Arctic suggest strong seasonal differences in habitat use by some sharks, with shallower mean depths (<300 m) occupied during winter. Significantly warmer water is occupied during winter and spring compared with fall and summer (Hussey and Devine, unpublished data).

Figure 9. Depth-temperature profile of an individual Greenland Shark tagged with a PSAT tag (Mk-10, Wildlife Computers, Inc.) in the Canadian Arctic (tag ID 44404; Campana et al. 2015).

It is uncertain whether ontogenetic shifts in habitat use occur, and the relative importance of various habitats to each life stage is poorly understood. Sharks of all sizes have been observed in both inshore and offshore habitats. The only documented pregnant females were caught near the fjords of the Faroe Islands (Koefoed 1957) and Norway (Bjerkan 1957). Juvenile sharks (defined as individuals < 200 cm by Hussey et al. 2015) have been reported from offshore waters around Greenland and Iceland (Kondyurin and Myagkov 1983; Nielsen et al. 2014), the southern Barents Sea (Rusyaev and Orlov 2013), and inshore within the fjords of eastern Baffin Island (Hussey et al. 2015; Devine et al. 2018). Yano et al. (2007) suggested that size distribution varies with depth in West Greenland, with both small sharks measuring less than 150 cm and large sharks measuring more than 400 cm found in deeper waters. This is supported by similar reports of small sharks in deep waters greater than 900 m in the Baffin region (Nielsen et al. 2014; Hussey et al. 2015; Hedeholm et al. 2018); however, juveniles have also been observed at depths as shallow as 600 m along east Baffin Island (Devine et al. 2018).

Movements, migration, and dispersal

Tagging studies confirm Greenland Sharks are capable of long-distance movements based on distance between tagging and pop-up locations of satellite tagged sharks [1,615 km over 170 days after tagging in Cumberland Sound, Nunavut (Campana et al. 2015); 980 km over 59 days, tagged in Svalbard, Norway (Fisk et al. 2012); 1,495 km over 287 days, tagged in Grise Fiord, Nunavut (Hussey and Devine, unpublished data)]. Some Greenland Sharks tagged in Canadian waters were observed to migrate to or between the waters of neighbouring countries including Greenland and the United States (Campana et al. 2015; Hussey et al. 2018).

Recent multi-year studies of more than 100 sharks in the Canadian Baffin region, using static acoustic telemetry, observed shark residency in inshore, deep-water fjords and sounds throughout Nunavut was restricted to ice-free periods from late July to early November. Offshore detections in Davis Strait occurred predominantly in December/January and May/June (Edwards et al. 2022). It is possible that offshore detections in these months occur as sharks transit through Davis Strait to access warmer waters further south. Long-term satellite tag deployments (>300 days; n = 13) indicate that tagged sharks spent approximately 50% of the year at temperatures between 5°C and -7°C—temperatures only accessible south of Davis Strait during this period (Curry et al. 2014; Hussey and Devine, unpublished data). Other long-term tagging (48 to 350 days) of Greenland Shark captured in Cumberland Sound showed pop-up localities ranging from the Labrador Sea to the northern extent of Baffin Bay, further supporting potential migratory pathways between these regions (Campana et al 2015). The scale of annual long-distance movements by Greenland Sharks may be underestimated if some sharks are seasonally migrating between the High Arctic to the Labrador Sea region, a roundtrip migration distance of at least 2,000 km.

Edwards et al. (2022) found that some acoustic tagged individuals exhibited site fidelity to inshore waters where tagging occurred, or were detected across multiple years within the same offshore array. Long-term satellite tags (>300 days) reported a few sharks with pop-up localities occurring within approximately 100 km of tagging localities the following year; however, tags for most sharks popped up in other inshore and/or on-shelf habitats (Hussey and Devine, unpublished data). Overall, tracking research in Canada suggests that Greenland Sharks return to coastal regions (if not the same site) during late summer / early fall, possibly visiting multiple coastal areas and inlets during transit between Arctic waters and potential over-wintering habitats further south. It is unknown if observed long-distance movements and potential site fidelity behaviours are related to foraging or reproduction.

The importance of sea ice to the species and the influence of its seasonal presence on their movement is largely unknown. Their abundance inshore during summer, ice-free months has been widely reported (Fisk et al. 2012; Hussey et al. 2014; Campana et al. 2015; Devine et al. 2018), and long-term acoustic tagging found most sharks in Nunavut to leave inshore fjords at the onset of sea ice formation (Edwards et al. 2022). However, records of shark bycatch during winter through-ice fishing in Nunavut (Bryk et al. 2018) and Greenland (Jensen 1914), along with active acoustic tracking under sea ice (Skomal and Benz 2004), suggest at least some sharks frequent ice-covered inshore waters. In the 1990s, fishers in the Nunavut community of Pangnirtung reported seeing more Greenland Shark bycatch in the early winter period of the ice-fishing season (NIRB 2018). However, sharks tagged in the summer have not been reported inshore during ice-covered winter periods, suggesting the potential for disparate movement strategies among sharks in the Baffin region (Edwards et al. 2022). It is possible some sharks are resident in inshore habitats year-round or display prolonged or inverted inshore residency timing compared with summer tagged sharks. It is unknown how changes in sea ice phenology and extent due to accelerated climate change in the Arctic (IPCC 2023) will impact the behaviour of Greenland Sharks.

Interspecific interactions

Diet

Greenland Shark consumes a wide variety of prey items including fishes, crustaceans, molluscs, and some marine mammals (Yano et al. 2007; McMeans et al. 2012). Stable isotope analyses (Fisk et al. 2002; Leclerc et al. 2012; Nielsen et al. 2014) confirm their role as top predators, feeding on both benthic and pelagic resources (Fisk et al. 2002; McMeans et al. 2013), and the species may play an important role in Arctic food webs.

Diet analyses from Greenland identify fishes as the most important overall prey source for Greenland Shark, but regional differences were observed in the main species consumed. Atlantic Cod (Gadus morhua) is the main contributor in southwest Greenland, while wolffish (Spotted, Anarhichas lupus and Atlantic, A. minor) dominate in eastern Greenland, and both species along with a higher proportion of mammal tissue occur in northwest Greenland (Nielsen et al. 2014). Additional diet analyses off Greenland revealed an ontogenetic dietary shift, with smaller (<200 cm) sharks feeding predominately on squids and larger (>200 cm) sharks feeding at higher trophic levels on epibenthic and benthic fishes, including gadids, skates, flatfish, lumpfish, wolffish, redfish (redfish only in the largest sharks >400 cm), and seals (Nielsen et al. 2019). In Canada, stomach contents from Greenland Sharks collected in Cumberland Sound (n = 14) found predominantly Greenland Halibut, gastropods, and amphipods. The presence of fishing hooks suggested Greenland Halibut were most likely depredated off demersal longlines deployed at the time of sampling (Fisk et al. 2002). Four stomachs examined from sharks captured near Ste-Rose-du-Nord along the north shore of the Saguenay River in Quebec yielded mostly fish and squid remains, including a nearly whole Greenland Halibut in one stomach. Two stomachs contained marine mammal remains, one with seal and the other a cetacean assumed to be Beluga Whale based on colour and its seasonal presence in the Saguenay Fjord (Marcil et al. 2002). Stomach contents from North Baffin Island found seal, whale, and char offal in addition to a variety of benthic organisms including gastropods, amphipods, urchin, kelp, and several skate egg cases (Beck and Mansfield 1969).

Greenland Sharks are also opportunistic scavengers. This is supported by the presence of terrestrial mammals and scavenging amphipods in stomach content analyses (Nielsen et al. 2014), and numerous direct observations of sharks feeding on carrion (outlined below). Although never directly observed, some evidence suggests live capture of seals (Nielsen et al. 2014, 2019); however, much of the cetacean and land-associated mammal (for example, caribou/reindeer [Rangifer tarandus], Polar Bear [Ursus maritimus]) tissue is presumed to be derived from carrion consumption (Nielsen et al. 2014). Genetic tracing of Minke Whale (Balaenoptera acutorostrata) tissue found in Greenland Shark stomachs from Svalbard revealed that sharks had scavenged this material from offal discarded at sea during whaling operations (Leclerc et al. 2011). A Harbour Porpoise (Phocoena phocoena) calf, presumably stillborn and scavenged, was found in the stomach of a Greenland Shark caught off the northeastern slope of the Grand Bank of Newfoundland (Williamson 1963). Inuit hunters have reported wounds and scars on Beluga Whales in Nunavut, but attribute these to unsuccessful attacks by Orca (Orcinus orca) and Polar Bear with no evidence of shark-induced injuries. There are reports of Greenland Sharks attacking Narwhal (Monodon monoceros) carcasses following harvests; other observations of shark bites on Narwhals are reported, but it is unclear whether the Narwhals were alive or dead when bitten (Stewart 2001). Greenland Shark was once thought to be attacking live seals off Sable Island, attributing the species to “corkscrew” wounds on seal carcasses washing ashore (Lucas and Natanson 2010); however, new evidence suggests these mortalities are caused by adult male Grey Seals (Halichoerus grypus) (Brownlow et al. 2016; van Neer et al. 2021).

Predators and competitors

Remains of Somniosus spp. have been found in the stomach contents of Sperm Whales (Physeter macrocephalus) (Roe 1969; Kawakami 1980). Orcas in the Pacific Ocean are also known to consume Somniosus pacificus (Ford et al. 2011). As both whales are found within Greenland Shark range, they may be potential predators for the species. In addition, Greenland Sharks will cannibalize conspecifics caught in fixed fishing gears such as longlines and gillnets (Idrobo and Berkes 2012; Grant et al. 2020).

Parasites

Most Greenland Sharks are host to the parasitic copepod Ommatokoita elongata, which attaches to the cornea and is often present in both eyes. Infection rates are high (>90%) in the Eastern Canadian Arctic and waters surrounding Greenland; however, lower incidence of infection (<10%) has been observed in the St. Lawrence Estuary and in the Northwest Atlantic (Edwards et al. 2019). Histological examinations of infected eyes found extensive tissue damage and trauma that suggests severe vision impairment and potential blindness (Borucinska et al. 1998; Benz et al. 2002). Therefore, these deep-water sharks presumably rely very little on vision, which may be supported by the presence of well-developed olfactory organs (Ferrando et al. 2016). Additionally, a single account exists of the parasitic barnacle Anelasma squalicola collected from the cloaca of a Greenland Shark caught near Mittimatalik, Nunavut; however, as this is the first and only record of a parasite typically found on shark hosts in the Etmopteridae and Scyliorhinidae families, it might be an isolated or rare event (Ste Marie et al. 2024). The impact of parasites on survival/population is unknown.

Physiological, behavioural, and other adaptations

Greenland Shark appear to prefer cooler temperatures, with a majority of records occurring at temperatures below 5°C (MacNeil et al. 2012). Baited camera surveys from inshore Nunavut observed sharks at bottom temperatures between -1.1°C to 1.1°C, with limited shark presence in sub-zero deployments (Devine et al. 2018). Average bottom temperature of fishing sets where Greenland Shark was captured in DFO-NL surveys was 3.6°C (range: 0.9°C to -5.1°C) and 2.6°C (range: 0.1°C to 3.9°C) for fall and spring surveys, respectively (Simpson et al. 2018). Sharks tagged in the St. Lawrence Estuary recorded temperatures between -1.1°C and 8.6°C, with a majority of time spent at 4°C to 6°C (Stokesbury et al. 2005). Tagging by Campana et al. (2015) found sharks in the Arctic occupied a mean temperature of 2.6°C compared with 7.9°C by sharks in the NW Atlantic off the southern Grand Banks and Scotian shelf. This study highlights the wide thermal tolerance of the species, with tags reporting temperatures between -1.8°C and 17.2°C.

Other aspects of Greenland Shark physiology are not well known. Analyses of hemoglobin found potential adaptive implications related to oxygen affinity of Hb isoforms (Russo et al. 2017; di Prisco et al. 2020). Greenland Shark was found to possess a high blood O₂ affinity and small Bohr effect, commonly known to sluggish elasmobranchs, with only limited sensitivity of blood O₂ affinity observed under simulated warming ocean conditions (Herbert et al. 2017). Capture-induced stress response of Greenland Shark found weak positive correlation of blood lactate values with fishing depth and body length (Barkley et al. 2017), but correlations with water temperature or post-release survival and overall fitness of Greenland Shark bycatch are unknown.

Given their longevity, trophic position, and broad range in the Arctic, Greenland Shark have been the focus of a number of studies exploring bioaccumulation and contaminant dispersal/distribution in Arctic waters. It is known to bioaccumulate inorganic and organic contaminants in all tissues studied to date (di Prisco et al. 2020), although knowledge of the underlying mechanisms of biochemical and physiological adaptations necessary to determine vulnerability is limited (di Prisco et al. 2020).

Feeding frequency is unknown for Greenland Shark. Recently, mean field metabolic rate of Greenland Sharks over a one-year period was estimated at 25.48 ± 0.47 mg O₂ h^-1 kg^-0.84, corresponding to prey consumption rates for an average size shark (224 kg) to be 193 g of fish or 61 g of marine mammal tissue required per day (Ste Marie et al. 2022). Ste Marie et al. (2022) further suggest that, depending on temperature and potential for Greenland Sharks to store energy in their tissues, a single juvenile seal (approximately 25 kg) could provide sufficient caloric value to sustain a shark for more than 365 days without feeding. This may be supported by observation of a seal pup found intact in the stomach contents of a Greenland Shark caught near Pond Inlet, Nunavut well after the pupping season, suggesting the seal pup had been consumed approximately 5 months prior (NCRI 2024). These low energy requirements combined with opportunistic and generalist foraging behaviour suggest Greenland Shark likely possess a large niche breadth and may be relatively resilient to periods of limited food availability.

Recent genome sequencing revealed Greenland Shark possesses one of the largest non-tetrapod genomes in the animal kingdom at 6.45 Gb (Sahm et al. 2024). This analysis also found 70.6% of the genome comprised of repeat content, the highest level reported among sharks. Genes specifically duplicated within the Greenland Shark genome appear to form a network of functionally related genes involved in DNA repair, which may support the longevity observed in this species.

Limiting factors

The main limiting factors for Greenland Shark are slow growth, late maturation, unknown but potentially limited fecundity, unknown reproductive periodicity, and remarkably long generation length—all traits associated with a low intrinsic population growth rate that could constrain species recovery (See Biology section).

Population sizes and trends

Data sources, methodologies, and uncertainties

No population assessments have been conducted to estimate the abundance of Greenland Shark and there are currently no data available on the population size of the species in Canada. All information available on abundance and trends is derived from fishery-dependent data, with the exception of an attempt to estimate local abundance in inshore Nunavut using baited cameras.

Fishery data sources include historical directed catch for liver oil, bycatch recorded in fisheries logbooks, and observations by At-Sea Observers (ASO) within fisheries. There is uncertainty with historical catch numbers given landings were often reported as “barrels of liver oil,” requiring estimates of the number of sharks needed to produce a barrel. Contemporary bycatch numbers are also highly uncertain, as Greenland Shark bycatch is still largely reported only as total catch weight rather than the number of sharks, with the exception of ASOs reporting to the DFO Arctic region, who have been required since 2016 to provide shark lengths, from which catch numbers can be derived. Further, as underreporting can occur within fisheries logbooks, and most Canadian fisheries have an estimated less than 5% actual ASO coverage (Bowlby et al. 2024), bycatch values underrepresent true removals to an unknown degree. Available bycatch data for Greenland Shark are not publicly accessible, nor are data on commercial effort and actual ASO coverage, which would be required to scale observed values and generate fleet-wide Greenland Shark bycatch estimates. These data were not provided; therefore, these estimates have not been produced. Fleet-wide bycatch totals have been estimated for other shark bycatch species (for example, Porbeagle [Lamna nasus]; Bowlby et al. 2024), and this remains a valuable exercise for evaluating potential fishing-related mortality; however, it should be noted that the low ASO coverage (<5%) in most fisheries would still likely result in underestimation of total bycatch rates.

A baited camera survey occurred during late summer of 2015 and 2016 in waters within and adjacent to the Tallurutiup Imanga National Marine Conservation Area, near Igloolik and Ikpiarjuk (Figure 4), and used existing models to estimate theoretical densities of sharks among sampling sites (Devine et al. 2018). However, these estimates are subject to several assumptions, apply only to summer months, and are from a comparatively small portion of Greenland Shark distribution. Therefore, they can only be used to generate estimates of local abundance.

The IUCN Red List Assessment for Greenland Shark by Kulka et al. (2020) presents the first attempt at population reconstruction for the species. Population estimates by Kulka et al. (2020) were reconstructed using a Schaeffer-logistic population model under multiple scenarios of carrying capacity and generation lengths. This provided a range of population estimates; however, there is high uncertainty in life history parameters required for model inputs (see Supplementary Materials of Kulka et al. 2020 for more details). Further information on Greenland Shark reproductive output, mortality rates, age at maturity, and lifespan is needed to reduce uncertainty in estimates of current population size and trends.

Abundance

There are currently no estimates of the number of Greenland Sharks in Canadian waters or globally. Given their broad geographic range extending into seasonally ice-covered waters, poor resolution of inshore-offshore movements, and potential for seasonal north-south migrations, traditional survey methods for estimating abundance are challenging and may not produce comprehensive estimates.

Baited camera surveys estimate that local densities inshore during late summer can be high (>10 individuals km²) in some regions of the eastern Canadian Arctic and are composed mainly of immature sharks with an average length of approximately 2.5 m (Devine et al. 2018). However, density estimates are site-specific and therefore cannot be used to infer broader abundance estimates. Hedeholm et al. (2018) suggested potential abundance of 100,000 individuals along the West Greenland Shelf between Upernavik and south Greenland, based on annual demersal trawl surveys. Catchability of Greenland Sharks in survey trawls is not well known, so it is uncertain how well survey catches reflect true abundance.

Fluctuations and trends

Inconsistent and/or unreliable bycatch data prevent assessment of trends or fluctuations in Greenland Shark bycatch rates over time. Annual dive surveys conducted at the same site in Baie-Comeau (St. Lawrence Estuary, Quebec) from 2003 to 2012 frequently observed Greenland Shark each year until numbers started to decline, around 2008. Only a single shark was observed in 2012 and there have been no observations since, despite a similar level and timing of diving effort in the region and occasional shark sightings elsewhere within the St. Lawrence Estuary (Gallant pers. comm. 2023). However, it is unknown if these changes are the result in shifts in distribution or a decline in abundance.

For decades, Fisheries and Oceans Canada has conducted annual multi-species trawl surveys that occasionally encounter Greenland Shark. However, variability in deep strata coverage, intermittent underreporting in some areas when numerous sharks are caught together resulting in an “invalid” tow where catch may not be recorded, and overall low or variable catch rates with relatively short tow times, prevent use of these data for examining trends over time.

An annual benthic longline survey has been conducted in Cumberland Sound as part of a Greenland Halibut stock assessment since 2011. This survey regularly encounters Greenland Shark as bycatch; however, catch rates are highly variable throughout the time series and no significant trends in abundance have been observed (Hedges pers. comm. 2024).

Population trajectories produced in the IUCN species assessment by Kulka et al. (2020) represent the only attempt at exploring potential population changes and trends over time. Populations were reconstructed using a Schaeffer-logistic population model testing three scenarios of potential carrying capacity across three generation length scenarios, given high uncertainty in life history parameters. These three scenarios yielded a wide range of results with high uncertainty associated with uncertain or unknown life history parameters and fisheries removals over time. Their preferred scenario used a moderate generation length of 150 years and estimated the population has declined by 57% over the last 420 years (ranging between 9% and 100%); however, other scenarios resulted in declines estimated from 1% to 100%, providing little clarity on population trends. This high uncertainty makes interpretation of these results challenging, and it is unclear whether the Canadian population follows this global trend.

Rescue effect

Tagging studies indicate strong connectivity across Baffin Bay (between Canada and Greenland) and the movement of sharks between Baffin Bay and waters south of Davis Strait, as well as further south between Canada and the U.S. Outside of these regions, the extent of mixing between the western and eastern portions of their range is unknown. Canada represents only a portion of available habitat for Greenland Sharks. It is unknown whether reproduction occurs in Canadian waters: a majority of Greenland Sharks observed in the Canadian Arctic appear to be immature juveniles (Hussey et al. 2014; Devine et al. 2018), suggesting mating is unlikely to occur there; however, larger, potentially mature individuals have been observed in Atlantic Canada (Simpson et al. 2018), but additional data on maturity in southern Canada is required. Large mature individuals and near birth-sized neonates have been observed outside Canada, suggesting mating and pupping may occur elsewhere (Nielsen pers. comm. 2024); however, it is unknown whether this could mitigate declines in Canadian waters.

Threats

Historical, long-term, and continuing habitat trends

The relative importance of various habitats across Greenland Shark life stages is unknown and movement ecology is poorly resolved. Therefore, there are limited data to assess changes to habitat quantity and quality for the species. Greenland Shark has a broad geographic range and is known to occupy a wide range of depths and temperatures, but with a notable preference for colder waters. Since these regions are experiencing climate change at an accelerated rate (IPCC 2023), it is certain that climate change will affect habitats occupied by Greenland Shark. Further, climate change is expected to enable the expansion of fisheries seasons and activity further north in increasingly ice-free waters and potentially increased effort following boreal species shifting further north (Tai et al. 2019), which could lead to increases in fishing threats to Greenland Shark (see Current and Projected Future Threats below).

Current and projected future threats

Greenland Shark is vulnerable to the cumulative effects of various threats, including overfishing through incidental capture as bycatch. The nature, scope, and severity of these threats are described in Appendix 1, following the IUCN-CMP (International Union for the Conservation of Nature – Conservation Measures Partnership) unified threats classification system (see Salafsky et al. 2008 for definitions and Master et al. 2012 for guidelines). The threat assessment process consists of assessing impacts for each of 11 main categories of threats and their subcategories, based on the scope (proportion of population exposed to the threat over the next 10-year period), severity (predicted population decline during the next 10 years or three generations, whichever is longer up to approximately 100 years), and timing of each threat. The overall threat impact is calculated by taking into account the separate impacts of all threat categories and can be adjusted by the species experts participating in the threats evaluation.

The overall threat impact for Greenland Shark is rated as Unknown based on an accumulation of credible threats for which the Severity of the threats is Unknown.

IUCN category 5 biological resource use

5.4 fishing and harvesting aquatic resources

Greenland Shark is reported as incidental bycatch in a wide variety of trawl, demersal longline, and gillnet fisheries throughout its range. One study estimated that at least 3,500 individuals may be captured globally as bycatch each year (see Kulka et al. 2020) based on available published data and fisheries ASO reports. However, this number may be considered a gross underestimate of the true number for several reasons: many fisheries encountering Greenland Shark bycatch have much less than 100% ASO coverage (actual coverage 0 to 5%), variable logbook returns and reporting rates, and data are not available for all fishing areas (Wheeland et al. 2018). Further, catch numbers have historically not been recorded and are still not available in most fisheries. Rather, only data on visually estimated total catch weight are collected, from which shark number estimates have been derived based on an assumed average weight of an individual adult shark.

In Canada, data on Greenland Shark bycatch comes largely from at-sea fisheries observers. Observer data suggest Greenland Shark bycatch in Canadian waters in the late-1980s was ≥ 800 tonnes (approximately 3,200 individuals based on observed sets only), but was significantly reduced with the introduction of the Nordmore grate in demersal shrimp trawl fisheries and potential reduction in trawled area in the early 1990s (MacNeil et al. 2012; Kulka et al. 2020). Current bycatch in Canada largely comes from offshore Greenland Halibut demersal trawl, longline, and gillnet fisheries and other deep-water fisheries. Greenland Shark bycatch has been reported from fisheries occurring within the following NAFO divisions (fishery-specific data not publicly available or provided by DFO: NAFO Div. 0AB, 2GHJ, 3KLNOPs, 4RST, 4VC, 4VN, 4 W, and 4X Figure 5). Greenland Shark bycatch also occurs in small-scale, inshore longline fisheries such as that in Cumberland Sound, Nunavut. Mean shark bycatch in the Cumberland Sound winter longline fishery was estimated at 1.1 sharks per 1,000 hooks (1989 to 2006), but bycatch in a summer open water fishery there was dramatically higher in 2009, with a mean of 6.3 sharks per 1,000 hooks (Bryk et al. 2018).

Species distribution models exploring spatio-temporal variability in Greenland Shark bycatch in the Northwest Atlantic found highest shark bycatch in deeper waters of NAFO Subareas 2 and 3, and a higher rate of shark bycatch relative to fishing effort during periods from December to March and August to September (Simpson et al. 2021). Similar modelling in the Baffin Bay region found high bycatch probability in coastal waters of NAFO Div.0A, but higher bycatch / larger sharks in northern Davis Strait (Div.0B), with overall results indicating higher bycatch in winter months compared with summer months in Baffin Bay (Yan et al. 2022).

At-Sea Observer records for total Greenland Shark bycatch from all fisheries indicates annual bycatch from 2000 to 2021 ranged from 51 to 198 tonnes (mean 125.5 t per year; Simpson pers. comm. 2023). Assuming an average shark weight of 250 kg, this corresponds to an estimated 204 to 792 individuals (mean 502.2 sharks per year) caught each year (Table 1). It should be noted that these values are observed bycatch only are not scaled up based on ASO coverage, and many fisheries do not have 100% ASO coverage. For example, many Atlantic Canadian fisheries have only 0 to 5% ASO coverage annually (DNV, 2024), although coverage of trawl fisheries in NAFO SA0A and SA0B is close to 100%. Observer coverage in other areas is inconsistent and at lower levels; plus there are differences in published reports of bycatch such that any estimates from observer data can only be regarded as underestimates (perhaps substantially so) of the true bycatch of Greenland Shark. Additional data are required to resolve uncertainty in bycatch estimates. Observed bycatch data for this report were not provided as a time series per fishery, and the data necessary to calculate observer coverage among fleets were not publicly available, preventing any scaling adjustments to estimate fleetwide bycatch of Greenland sharks in Canada.

Although all Greenland Shark bycatch is released in Canada, both at-vessel mortality (sharks dead upon capture) and post-release mortality (sharks that die from capture-stress or injury in the days or weeks following release) rates of discarded sharks are not well known and likely vary across gear types. For mobile gear like bottom trawls, the proportion of sharks dead upon release was notably higher (approximately 36% compared with approximately 16% for longlines; Bryk et al. 2018) and positively correlated with both set duration and total catch weight in the trawl. Bycaught Greenland Shark released with pop-up satellite tags to estimate 30-day post-release mortality following trawl encounters suggest approximately 35% of sharks released alive do not survive (n = 41 sharks; Hussey and Devine, unpublished data). Handling and discard methods likely vary across fisheries and vessels, but could have a significant impact on discard survival; additional research is required to determine how certain practices, such as craning sharks overboard by the tail, impact survival post-release. Discard mortality rates are thought to be much lower for longline gear, particularly if sharks are simply hooked by the mouth and are handled carefully upon release (that is, de-hooking without damaging the jaw, minimizing time at the surface). However, Greenland Sharks captured on longlines are prone to entanglement in the mainline which, if wrapped too tightly around the body, may result in higher mortality rates through strangulation or injuries incurred during efforts to detangle sharks from the gear. Mortality rates from gillnet fisheries are unknown, but presumed to be high given these sharks are ram-breathers and 100% at-vessel mortality has been observed in fixed gillnets for other ram-breathing species due to suffocation (Bowlby et al. 2024). Furthermore, bait has recently been added to gillnets fishing in the Canadian Arctic and Atlantic Canada, which has been shown to increase catch-per-unit-effort of Greenland Shark bycatch compared with non-baited gillnets (Bayse and Grant 2020). Stomach content analyses from sharks captured from the Saguenay River in Quebec documented a piece of gillnet mesh in one stomach (Marcil et al. 2002) and fishing net has been found in the intestine of Greenland Shark caught near Pond Inlet, Nunavut (NCRI 2024), suggesting sharks may incidentally consume fishing gear, possibly when attempting to depredate entangled fishes or bait. More information on post-release mortality across all fishing gears, and accurate estimates of current bycatch levels are needed to inform appropriate fishing mortality limits for Greenland Shark.

Few bycatch mitigation efforts have been explored to reduce Greenland Shark bycatch, following the introduction of the Nordmore grate excluder to the demersal shrimp trawls, and these efforts have been exclusively in demersal longline fisheries. In Cumberland Sound, longline gear modification experiments found gangions composed of monofilament caught fewer Greenland Shark compared with the braided nylon material currently in use (Grant et al. 2020). A single study by Grant et al. (2018) further explored the potential of electropositive metal hooks as deterrents to reduce Greenland Shark bycatch. Unfortunately, this study did not observe Greenland Sharks to be deterred by the presence of magnetic material wrapped around hooks and it did not reduce overall bycatch rates.

Warming Arctic waters have resulted in longer open-water seasons and increased potential for more southerly commercial species to expand northward. This potential for new fisheries to develop along with expansion of existing fisheries into previously unfished waters further north could result in increased rates of Greenland Shark bycatch in the future (Edwards et al. 2019).

Greenland Shark is often perceived as a nuisance for fisheries, leading to some past and present persecution and attempts to control local shark abundance. Reports of bycaught sharks having tails removed prior to release are known in Canada, Iceland, and Greenland (Davis et al. 2013). Castro et al. (1999) note government-subsidized removal of Greenland Shark to reduce population levels in western Norway during the 1970s. Similarly, municipalities in western Greenland have, in the past, provided bounties to fishers in exchange for shark snouts in efforts to reduce local Greenland Shark abundance. Although bounties are no longer in place, the perception of Greenland Shark as a pest that contributes to gear and catch loss continues, and as a result, sharks may be killed before being discarded. It is unknown to what extent persecution and control persist, and no estimates of shark mortality attributed to this threat are available.

For centuries, Greenland Shark was the target of directed fisheries for its liver oil, primarily in Greenland, Iceland, Norway, and Russia (FAO 2022). The earliest records date back to 1624, with a reported 111,600 litres of liver oil exported and subsequent annual exports ranged from 29,280 to 209,040 litres. Given 1.5 barrels of raw liver was required to produce 1 barrel of oil (~120 litres per barrel), and a 4.2 m Greenland shark with an approximately 50 kg liver (MacNeil et al. 2012) would produce approximately 33 litres, this equates to an estimated 3,382 sharks harvested in 1624 and between 887 and 6,334 sharks annually in subsequent years. Harvests continued and increased demands in Europe led to expansions in the shark fishery throughout the 19th century, growing from an estimated 7,364 sharks (2025 barrels of oil) in 1819 to 47,273 sharks (13,000 barrels of oil) in 1867 (MacNeil et al. 2012). Over 32,000 individuals were reported from harvests in Greenland by 1910 (Jensen 1914) and catch peaked shortly after, with Norway reporting 2.8 million kg of liver oil (approx. 58,000 individuals) in 1948 (MacNeil et al. 2012). By the 1960s, the fishery had ceased due to falling market prices for liver oil with the development of synthetic oils (FAO 2022). Since the end of the liver oil fishery, Greenland Sharks have continued to be the target of artisanal, small-scale fisheries in Iceland and Greenland. Sharks are primarily caught with demersal longlines or hook and line gears and occasionally gillnets. Since 1980, the United Nations Food and Aquaculture Organization (FAO) reports annual catch ranging from 6 to 163 tonnes, with a mean of approximately 52 tonnes per year during this time period. In recent years the FAO reports an increase in Greenland Shark catch, with a mean annual catch of 98 tonnes in the past five years (Figure 10; FAO 2022).

Figure 10. Annual catch (tonnes) of Greenland Shark reported by the FAO (FAO 2022).

Historical subsistence use by Greenlandic Inuit includes the use of shark skin for boots and creating knives by embedding shark dental bands in other materials (FAO 2022). Greenland continues a small-scale individual subsistence harvest of Greenland Shark in northwest and eastern Greenland for human consumption and as a source for sled-dog food (Hedeholm et al. 2018). The meat may be considered toxic when fresh and if consumed in large quantities, so it is most often treated through washing or fermentation prior to consumption (MacNeil et al. 2012).

IUCN category 11 - Climate change and severe weather

11.1 Habitat shifting and alteration

Given that Greenland Shark primarily inhabits Arctic and sub-Arctic waters where the impacts of anthropogenic climate change are pronounced and occurring at an accelerated rate (IPCC 2023), it is possible the species may experience changes to habitat that could impact its distribution, fitness, and population dynamics in Canada. Warming temperatures in part have led to a reduction in annual mean sea-ice extent by 3.5% to 4.1% per decade between 1979 and 2012, and under high emission scenarios the Canadian Arctic could be ice-free in the summer by the end of the 21st century (IPCC 2023). Direct impacts on the species are unclear. There is some evidence to suggest seasonal sea ice may be a driver of Greenland Shark movements (Edwards et al. 2022) and changes in sea ice phenology could have negative impacts on the prey dynamics in the region (Edwards et al. 2019). It is uncertain how sensitive or adaptive Greenland Sharks may be to these impacts. As the species tolerates a wide range of temperatures (see Habitat section), has a broad geographic range including occurrences in deeper waters well beyond its core distribution (see Distribution section), and combined with its capability for long-distance movements (see Movements, Migration, Dispersal section) and opportunistic/generalist foraging behaviour with potentially low energy requirements, it is possible that Greenland Shark has a high adaptive capacity and/or ability to locate away from these impacts.

Number of threat locations

Greenland Sharks are highly mobile and capable of transiting long distances, with individuals observed to occupy a wide range of habitats across the North Atlantic and Arctic regions. At present, the species is believed to be a single population, with the primary threat of incidental bycatch applied throughout its range, both within and outside Canadian waters. As the species is susceptible to capture in a variety of fishing gears and is highly mobile, in the absence of any gear modifications to mitigate capture, the threat of bycatch is presumably anywhere fisheries and the species’ range overlaps; thus a single location is used.

Protection, status, and recovery activities

Legal protection and status

Greenland Shark is not listed under the Species at Risk Act (2002), nor is it protected or regulated under any provincial, territorial, or other Canadian federal legislation. In Canada, incidental capture of sharks in commercial fisheries are to be released alive if they are not to be landed, but no specific guidelines for Greenland Shark handling and release or bycatch limits are in place. The species is also not listed under the Endangered Species Act in the U.S., nor is it listed under legislation within any other country where it is found (for example, Greenland [Denmark], Iceland, Norway, Russia).

The North Atlantic Fishery Organization (NAFO) includes protective measures for Greenland Shark within Article 12 of the NAFO Conservation and Enforcement Measures, including prohibition of NAFO fishing vessels conducting a directed fishery for the species and requiring “every vessel to undertake all reasonable efforts to minimize incidental catch and mortality, and where alive, release Greenland Sharks in a manner that causes the least possible harm” (NAFO, 2022). Following the 44th NAFO Annual Meeting in September 2022, member parties further agreed to a prohibition of Greenland Shark retention within the NAFO Regulatory Area.

Non-legal status and ranks

Greenland Shark is not globally ranked (GNR) by NatureServe, but provincial statuses are provided for Nunavut (No Status Rank) and Quebec (S4-Apparently Secure). As of 2020, their Rounded National Rank is considered to be “Apparently Secure” (N4) and subnational conservation status of “Apparently Secure” (S4) in the Atlantic Ocean and “Unrankable” (SU) in the Eastern Arctic Ocean (Canadian Endangered Species Conservation Council 2022).

In 2020, the IUCN Red List reassessed Greenland Shark and changed its designation from “Near Threatened” to “Vulnerable” based on population reconstruction estimates that found evidence of decreasing population trends along with persistent risks from fisheries encounters as bycatch.

Land tenure and ownership

The distribution of Greenland Shark overlaps with several protected and conserved marine areas throughout eastern Canadian waters, including the Disko Fan, David Strait, and Hatton Basin Conservation Areas, and the Northeast Newfoundland Slope Closure. Larger closed areas further north, such as the Tallurutiup Imanga National Marine Conservation Area, also overlap, but it is uncertain whether fishing (See Threats section for potential impacts) may still occur there. However, these protected areas represent only a small portion of Greenland Shark range of occurrence in Canada. Additional protected areas are expected to be secured in the future as Canada aims to meet conservation targets, but it is unknown how or if these protected areas will benefit the Greenland Shark population.

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Collections examined

No collections were examined for the preparation of this report.

Authorities contacted

• Pirie-Dominix, L. Canadian Wildlife Service – Northern region: Nunavut
• Jackson, S.F. Canadian Wildlife Service – Atlantic region
• Ilves, K. Research Scientist. Canadian Museum of Nature. Ottawa, Ontario
• Doubt, J. Canadian Museum of Nature. Ottawa, Ontario
• De Forest, L. Parks Canada
• Shepherd, P. Parks Canada
• Snook, J. TJFB
• Taylor, C. TJFB
• Schnobb, S. COSEWIC Secretariat
• Ritchie, K. Habitat and Species at Risk Biologist. Nunavut Wildlife Management Board
• Gallant, J. Scientific Director. St. Lawrence Shark Observatory
• Diment, J. Fisheries and Oceans Canada
• Gauthier, Isabelle. Coordonnatrice provinciale des espèces fauniques menacées et vulnérables, Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs
• Cardinal, N. COSEWIC ATK SSC

Acknowledgements

Funding for the preparation of this report was provided by Environment and Climate Change Canada.

Biographical summary of report writer(s)

Dr. Brynn Devine received her BSc in Marine Biology at Texas A&M University (Galveston) and her MSc in Tropical Marine Ecology at James Cook University in Queensland, Australia. She earned her PhD from Memorial University of Newfoundland, where her research explored the environmental drivers of deep-sea fish distributions in Atlantic Canada and the Eastern Arctic, including Greenland Shark in Nunavut. In 2021, she completed a Liber Ero Postdoctoral Fellowship at the University of Windsor with a focus on Greenland Shark movement ecology and fisheries interactions in northern deep-water fisheries. She is currently an Arctic Fisheries Scientist with the non-profit Oceans North, where she continues to study Greenland Sharks and other elasmobranchs in eastern Canada.

Appendix 1. Threats calculator

Species or Ecosystem scientific name: Somniosus microcephalus, Greenland Shark

Date: 2025-01-14

Assessor(s): Dwayne Lepitzki (facilitator), Jena Edwards, Sabrina Crowley, Kevin Hedges, Matthew Webb, Heather Bowlby, Mark Simpson, Jennifer Diment, Hugues Benoit, Pasan Samarasin, Tommy Palliser, Monica Engel, David Keith, and Nigel Hussey

References: Draft calculator provided along with 6-month COSEWIC report; teleconference from January 8, 2025.

Assigned overall threat impact:

U = Unknown

Impact adjustment reasons:

Multiple recognized threats with Unknown impacts

Overall threat comments:

This is a large sleeper shark species known to inhabit polar waters. It is the largest fish in Arctic waters and is currently believed to be among the longest-living vertebrates. It is found from surface waters to at least 2,900 m throughout the North Atlantic Ocean and adjacent Arctic waters, extending throughout Atlantic Canada and the eastern Canadian Arctic, across Greenland and Iceland. In Canada, a seasonally higher abundance of the species has been observed in inshore fjords of Nunavut in summer months. Tagging studies confirm it is capable of long-distance movements, and fish tagged in Canadian waters were observed to migrate to or between waters of neighbouring countries including Greenland and the United States. There are currently no estimates of the species population size in Canadian waters, hence population size and trends in abundance are considered unknown. Reproductive potential, litter size, gestation period, and length of reproductive cycle are uncertain. Generation time is likely between 150 and 200 years, based on current estimates of age-at-maturity and longevity. Anthropogenic activities are the most significant threat to the species. It is reported as incidental bycatch in a wide variety of trawl, longline, and gillnet fisheries throughout its range, with estimates of at least 3,500 sharks bycaught in fisheries each year; however, bycatch data are poor and this is likely underestimated. Greenland Shark remains the target of directed artisanal, small-scale fisheries in Iceland and Greenland. The extreme life history traits of the species, including remarkably slow growth, late maturity, and longevity, make it particularly high-risk to overfishing. Given that it primarily inhabits regions experiencing climate change impacts at an accelerated rate (two to four times faster in the Arctic compared with the global average), it is possible the species may experience changes to habitat that could impact their distribution, fitness, and population dynamics in Canada. The time frame for scoring severity and timing is 100 y (maximum allowable). Threats assessed to Canadian population, including threats outside Canadian waters. The species was globally designated as Vulnerable under criteria A2bd. In 2022, the North Atlantic Fisheries Organization (NAFO) agreed to a ban on retention of the species for all fisheries occurring within NAFO Regulatory Areas. Although most sharks are released, post-release survivorship of bycatch is largely unknown.

Classification of Threats adopted from IUCN-CMP, Salafsky et al. (2008).