|Scientific Name:||Cystophora cristata|
|Species Authority:||(Erxleben, 1777)|
Cystophora antillarum Gray, 1849
Phoca cristata Erxleben, 1777
|Taxonomic Notes:||Morphometric and allozyme analyses, as well as molecular genetics analyses, suggest that Hooded Seals are a single panmictic population (Wiig and Lie 1984, Sundt et al. 1994, Coltman et al. 2007), though three breeding stocks are commonly recognized (Gulf and St Lawrence and the Front (east coast Canada), the Davis Strait and the West Ice (Greenland Sea north of the island of Jan Mayen)) (Sergeant 1974, Lavigne and Kovacs 1988).|
|Red List Category & Criteria:||Vulnerable A2b ver 3.1|
|Assessor(s):||Kovacs, K. (IUCN SSC Pinniped Specialist Group)|
|Reviewer(s):||Kovacs, K. & Lowry, L. (Pinniped Red List Authority)|
Hooded Seals in the northwest Atlantic breeding areas are currently either stable or increasing modestly. However, the northeast Atlantic stock has declined by 85-90 % over the last 40-60 years. The cause of the decline is unknown, but very recent data suggests that it is on-going (30% within 8 years), despite the protective measures that have been taken in the last few years. Although the Hooded Seal is thought to be panmictic, the precipitous decline in the eastern stock (from over half a million to 70 000) over a period of a few decades warrants that the hooded seal be classified as Vulnerable.
IUCN Evaluation of the Hooded Seal, Cystophora cristata
Prepared by the Pinniped Specialist Group
A. Population reduction Declines measured over the longer of 10 years or 3 generations
A1 CR > 90%; EN > 70%; VU > 50%
Al. Population reduction observed, estimated, inferred, or suspected in the past where the causes of the reduction are clearly reversible AND understood AND have ceased, based on and specifying any of the following:
(a) direct observation
(b) an index of abundance appropriate to the taxon
(c) a decline in area of occupancy (AOO), extent of occurrence (EOO) and/or habitat quality
(d) actual or potential levels of exploitation
(e) effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.
Generation time in Hooded Seals is approximately 10 years. Hooded Seals have experienced a dramatic decline over the last three generations (30 years) in the northeast Atlantic stock but the causes are not clearly reversible, nor understood (global decline is, however, not > 50%).
A2, A3 & A4 CR > 80%; EN > 50%; VU > 30%
A2. Population reduction observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under Al.
Hooded Seals in the northeast Atlantic have experienced a dramatic decline over the past 40-60 years (the precise time-frame is not known). This stock has been reduced by 85-90% since World War II. It is currently in decline, the causes of which are unknown (the decline may not be reversible). The northwest Atlantic stock of hooded seals is stable or increasing moderately in recent decades. Overall, the global population has declined by approximately 35-40% and thus this species should be considered Vulnerable.
A3. Population reduction projected or suspected to be met in the future (up to a maximum of 100 years) based on (b) to (e) under A1
There is concern that Hooded Seal will be negatively impacted by climate-change induced alternations to sea ice extent and character, as well as potential changes in the ecosystem that will affect its food supply. The relatively restricted distribution and some degree of overlap in diet with commercial fisheries add to the risk factor for this species.
A4. An observed, estimated, inferred, projected or suspected population reduction (up to a maximum of 100 years) where the time period must include both the past and the future, and where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.
It is suspected that a population reduction will occur in the next 100 years for Hooded Seals due to climate-change induced alterations to the physical and biological resources upon which this species depends. A marked reduction has already been observed in the northeast Atlantic for unknown reasons. The decline has not ceased and may not be reversible.
B. Geographic range in the form of either B1 (extent of occurrence) AND/OR B2 (area of occupancy)
B1. Extent of occurrence (EOO): CR < 100 km²; EN < 5,000 km²; VU < 20,000 km²
The EOO of Hooded Seals is >20,000 km².
B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²
The AOO of Hooded Seals is > 2,000 km².
AND at least 2 of the following:
(a) Severely fragmented, OR number of locations: CR = 1; EN < 5; VU < 10
(b) Continuing decline in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) area, extent and/or quality of habitat; (iv) number of locations or subpopulations; (v) number of mature individuals.
(c) Extreme fluctuations in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) number of locations or subpopulations; (iv) number of mature individuals.
C. Small population size and decline
Number of mature individuals: CR < 250; EN < 2,500; VU < 10,000
Both segments of the hooded seal population exceed 10,000 mature individuals.
AND either C1 or C2:
C1. An estimated continuing decline of at least: CR = 25% in 3 years or 1 generation; EN = 20% in 5 years or 2 generations; VU = 10% in 10 years or 3 generations (up to a max. of 100 years in future)
C2. A continuing decline AND (a) and/or (b):
(a i) Number of mature individuals in each subpopulation: CR < 50; EN < 250; VU < 1,000
(a ii) % individuals in one subpopulation: CR = 90–100%; EN = 95–100%; VU = 100%
(b) Extreme fluctuations in the number of mature individuals.
D. Very small or restricted population
Number of mature individuals: CR < 50; EN < 250; VU < 1,000 AND/OR restricted area of occupancy typically: AOO < 20 km² or number of locations < 5
Both segments of the hooded seal population exceed 1,000 mature individuals.
E. Quantitative analysis
Indicating the probability of extinction in the wild to be: CR > 50% in 10 years or 3 generations (100 years max.); EN > 20% in 20 years or 5 generations (100 years max.); VU > 10% in 100 years
There has been no population viability analysis conducted on hooded seals.
Listing recommendation — The relatively restricted distribution of Hooded Seals, their dependence on sea ice for breeding, moulting and resting and the observed, significant, declines for unknown reasons in the northeast Atlantic stock suggest that upgrading of this species to Vulnerable is warranted under criterion A2b. The observation of increased numbers of vagrant Hooded Seals well beyond their normal range, on both sides of the North Atlantic, suggests that the global population of Hooded Seals is experiencing change throughout the species range, despite the contrasting population trends in the west and east.
|Range Description:||Hooded Seals are found at high latitudes within the North Atlantic; seasonally they extend their range north into the Arctic Ocean, as well as south into the North Sea in the Northeast Atlantic. They breed on pack ice and are associated with it much of the year, though they spend significant periods of time pelagically, without hauling out (Lavigne and Kovacs 1988, Folkow and Blix 1999). There are four major pupping areas: near the Magdalen Islands in the Gulf of St Lawrence, north of Newfoundland in an area known as the “Front,” the Davis Strait (Sergeant 1974) and in the West Ice in the Greenland Sea near the island of Jan Mayen. Hooded Seals wander extensively sometimes; young animals have come ashore as far south as Portugal and the Canary Islands in Europe and south into the Caribbean in the West Atlantic (Kovacs and Lavigne 1986). They are increasingly common in recent years on Sable Island and along the New England coast (Harris et al. 2001, Lucas and Daoust 2002). They have also been found outside the Atlantic in the eastern Beaufort Sea and an adult female stranded in southern California in 1992 (Dudley 1992, Rice 1998, Kovacs 2002). Since the mid 1990s large numbers of vagrant Hooded Seals have been found away from the Arctic in some years; the numbers of these sightings are increasing for unknown reasons (Mignucci-Giannoni and Haddow 2002, Harris and Gupta 2006).|
Native:Canada; Greenland; Iceland; Norway; United States
Vagrant:Argentina; Bahamas; Bermuda; Denmark; Faroe Islands; France; Germany; Ireland; Portugal; Puerto Rico; Russian Federation; Spain; Svalbard and Jan Mayen; Turks and Caicos Islands; United Kingdom
|FAO Marine Fishing Areas:||
Atlantic – northeast; Atlantic – northwest
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Aerial surveys carried out at all three whelping areas in the Northwest Atlantic in 2005 produced an estimate of 116,900 pups born. The whole population, modelled based on the pup counts, produced an estimate of 592,000 individuals (Waring et al. 2005). This suggests a moderate increase both in pup production and population size between the mid 1980s and 2005 (Hammill and Stenson 2006, 2007). Hooded Seals in the northeast Atlantic are showing an opposite trend. Pup production estimated for the Greenland Sea stock (West ice, near Jan Mayen) in 2005 was 15 250 pups, which in turn produces an estimate of total population size of about 70,000 animals (Øigård and Haug 2007, Salberg et al. 2008). This population estimate for the northeast Atlantic stock is 10-15% of the level observed some 60 years ago. Pup production estimated for this hooded seal whelping area in 1997 was 24,000. The cause of the significant, on-going decline in this population is unknown. But, concern for the apparent problems facing this stock has lead to the closure of hunting in recent years and the listing of this stock in the Norwegian Red List as Vulnerable (www.artsdatabanken.no).|
|Habitat and Ecology:||
Hooded Seals are a markedly sexually dimorphic ice-breeding pinniped. Adult male hooded seals average 2.5 m in length and 300 kg (Kovacs and Lavigne 1986), with large animals reaching over 400 kg (Kovacs 2002). Adult females are smaller, averaging 2.2 m and 160 kg, but can reach 300 kg (Kovacs and Lavigne 1992). Pups are born at approximately 1 m in length and 24 kg (Kovacs and Lavigne 1992).
Hooded Seals pup on pack ice in mid March. The breeding season for this polygynous species is very short, usually lasting only about 2.5 weeks, and mating takes place in the water (Boness et al. 1988, Kovacs 1990). This species has the shortest lactation period for any mammal, with most pups being weaned in four days (Bowen et al. 1985). Pups weigh an average of 48 kg at weaning in the Northwest stocks (Kovacs and Lavigne 1992, Lydersen et al. 1997). The short reproductive period is energetically advantageous to both males and females, with relative losses in body mass being small for both sexes compared to other phocid seals (Kovacs and Lavigne 1992, Kovacs et al. 1996).
Hooded Seals moult in July, with each breeding stock congregating at a separate, traditional site, north of their whelping areas. If mixing does occur, the degree to which this takes place is unknown. Following the moulting period each stock disperses in the North Atlantic; movement patterns are only documented for the Greenland Sea stock (Folkow and Blix 1995, 1999, Folkow et al. 1996). Apart from the breeding and moulting periods where Hooded Seals form loose aggregations in specific areas, it is thought that hooded seals live quite solitary lives. However, little is in fact known about them outside the periods when they congregate. Groups of females with young animals have been seen at the northern ice edge in summer, but it is not known whether the groups were socially facilitated or solely the result of concentrations of prey (Kovacs pers. Obs.). Hooded seal longevity is 25-30 years (Kovacs 2002).
Hooded Seals are very capable divers that spend extensive periods at sea without hauling out (Folkow and Blix 1999). Most of their dives are from 100-600 m in depth and last 5-25 minutes, however, very deep dives to over 1,000 m and dives lasting almost an hour have been recorded (Folkow et al. 1996, Lydersen et al. Unpubl. Data). Hooded Seals feed on a wide variety of fish and invertebrates, including species that occur throughout the water column. Examples of typical prey are Parathemisto, Greenland halibut, members of the cod family such as Polar and Atlantic Cod, redfishes (Sebastes spp.), sand eels, herring, capelin, squid (e.g. Gonatus fabricii), and shrimp (Haug et al. 2004, 2007).
Polar Bears and Killer Whales are known Hooded Seall predators (Lavigne and Kovacs 1988); Greenland Sharks might also take young Hooded Seals.
Hooded Seals were subjected to intense commercial hunting in the 19th and 20th centuries. Harvests were often conducted in association with Harp Seal harvests and commercial fisheries for Greenland Sharks. Norway, the former Soviet Union, Canada, and Greenland have all been involved in the commercial harvests of this species. Following World War II the hunt was primarily focused on pups because of their highly prized blue-back pelt, however, many adult females were taken when defending their pups (Lavigne and Kovacs 1988). The number of Hooded Seals in the northwest Atlantic is relatively well known. Pup production estimates have been repeatedly conducted, and TAC (total allowable catch) adjusted through time (e.g. Sergeant 1976, Hay et al. 1985, Bowen et al. 1987, Hammill et al. 1992, Stenson et al. 1996). Since 1998 TAC has been set at 10,000 seals per year, but catches are in fact only a few hundred animals (ICES 2006). Hooded Seals have also been harvested commercially in the Greenland Sea for centuries. The hunt increased substantially after World War II, to levels that were clearly not sustainable; regulatory measures were introduced in 1958 to reduce effort, and quotas were imposed in 1971 (Sergeant 1976, ICES 2006). Based on catch per unit effort analyses and mark-recapture pup production estimates it was assumed that the stock increased from the 1960s through to the 1990s at an unknown rate (Ulltang and Øien 1988). Aerial survey attempts in 1994 failed to produce an estimate (Øritsland and Øien 1995). Recent modelling efforts suggest that a very substantial decrease in population abundance took place from the late 1940s up to the early 1980s (ICES 2006). Aerial surveys in recent years suggest that this downward trend is continuing. Total pup production was estimated to be 24 000 in 1997 and this number dropped to 15 250 in 2005 (Salberg et al. 2008).
Hooded Seals are also taken by native people of Greenland and Canada for subsistence purposes every year (Kovacs 2002). By-catch of Hooded Seals in coastal net fisheries has been reported from the United States, from trawl fisheries off Norway and Newfoundland, and salmon drift nets used off Greenland (Woodley and Lavigne 1991, Reeves et al. 1992, Waring et al. 2005). Competition for food with commercial fisheries and other predators has been suggested as a factor that may limit population growth or lead to declines (Reijnders et al. 1993).
Impacts of oil spills on Hooded Seals have not been reported; however, as an ice breeding species, they might be at risk of mortality from spills during the pupping season when newborn and newly weaned pups could be fouled (St. Aubin 1990). Hooded Seals have been exposed to morbillivirus (Duignan et al. 1997), but did not suffer fatalities during the mass die-offs of Harbour Seals in European waters from phocine distemper virus in 1998 and 2002. Subsequent testing of a variety of Arctic seals revealed antibodies to the virus in 18-24% percent of the Hooded Seals sampled indicating exposure to the virus (Harkonen et al. 2006).
The Hooded Seal is a pack ice species, which is dependent on ice as a substrate for pupping, moulting, and resting and as such is vulnerable to reduction in extent or timing of pack ice formation and retreat (Tynan and DeMaster 1997, Johnston et al. 2005, Learmonth et al. 2006, Kovacs and Lydersen 2008, Laidre et al. 2008). The productivity of the ice edge ecosystem is also dependent on the dynamics and seasonality of arctic ice, and alterations to the cycle of formation and retreat could have negative effects on important Hooded Seal prey such as Arctic Cod. Decreases in sea ice cover could also lead to more shipping and development of extraction based industries in the Arctic which in turn could negatively affect Hooded Seals through increased exposure to contaminants and pollution, increased disturbance and increased risk of shipping accidents and spills (Pagnan 2000).
|Conservation Actions:||Numerous conservation measures, international management plans, harvest quotas, and agreements and treaties, have been developed for the conservation of Hooded Seals dating back to the 1870s. Moulting seals in the Denmark Strait have been protected since 1961. Harvest quotas at Jan Mayen began in 1971. Hunting was banned in the Gulf of St Lawrence in 1972 and quotas were placed on the rest of the Canadian harvest beginning in 1974. A European Economic Community ban on importation on seal products in 1985 reduced the harvest of blueback Hooded Seals through the loss of the primary market for the furs (Lavigne and Kovacs 1986, Reeves et al. 1992).|
Boness, D. J., Bowen, W. D. and Oftedal, O. T. 1988. Evidence of polygyny from spatial patterns of hooded seals (Cystophora cristata). Canadian Journal of Zoology 66: 703-706.
Bowen, W. D., Myers, R. A. and Hay, K. 1987. Abundance estimation of a dispersed, dynamic population: hooded seals (Cystophora cristata) in the northwest Atlantic. Canadian Journal of Fisheries and Aquatic Sciences 44: 282-295.
Bowen, W. D., Oftedal, O. T. and Boness, D. J. 1985. Birth to weaning in four days: extraordinary growth in the hooded seal (Cystophora cristata). Canadian Journal of Zoology 63: 2841-2846.
Coltman, D. W., Stenson, G., Hammill, M. O., Haug, T., Davis, S. and Fulton, T. L. 2007. Panmictic population structure in the hooded seal (Cystophora cristata). Molecular Ecology 16: 1639-1648.
Dudley, M. 1992. First record of a hooded seal, Cystophora cristata Erxleben, 1777. Marine Mammal Science 8: 164-168.
Duignan, P. J., Nielsen, O., House, C., Kovacs, K. M., Duffy, N., Early, G., Sadove, S., St. Aubin, D. J., Rima, B. K. and Geraci, J. R. 1997. Epizootiology of morbillivirus infection in harp, hooded, and ringed seals from the Canadian Arctic and western Atlantic. Journal of Wildlife Diseases 33: 7-19.
Folkow, L. P. and Blix, A. S. 1999. Diving behaviour of hooded seals (Cystophora cristata) in the Greenland and Norwegian Seas. Polar Biology 22: 61-74.
Folkow, L. P., Martensson, P. E. and Blix, A. S. 1996. Annual distribution of hooded seals (Cystophora cristata) in the Greenland and Norwegian Seas. Polar Biology 16: 179-189.
Hammill, M. O. and Stenson, G. B. 2006. Abundance of Northwest Atlantic hooded seals (81960-2005). DFO CSAS.
Hammill, M. O. and Stenson, G. B. 2007. Application of the precautionary approach and conservation reference points to the management of Atlantic seals. ICES Journal of Marine Science 64: 701-706.
Hammill, M. O., Stenson, G. B. and Myers, R. A. 1992. Hooded seal Cystophora cristata) pup production in the Gulf of St Lawrence. Canadian Journal of Fisheries and Aquatic Sciences 49: 2546-2550.
Harkonen, T., Dietz, R., Reijnders, P., Teilmann, J., Harding, K., Hall, A., Brasseur, S., Siebert, U., Goodman, S. J., Jepson, P. D., Rasmussen, T. D. and Thompson, P. 2006. A review of the 1988 and 2002 phocine distemper virus epidemics in European harbor seals. Diseases of Aquatic Organisms 68: 115-130.
Harris, D. E. and Gupta, S. 2006. GIS-based analysis of ice-breeding seal strandings in the Gulf of Maine. Northeastern Naturalist 13: 403-420.
Harris, D. E., Lelli, B., Jakush, G. and Early, G. 2001. Hooded seal (Cystophora cristata) records from the southern Gulf of Maine. Northeastern Naturalist 8: 427-434.
Haug, T., Nilssen, K. T. and Lindblom, L. 2004. Feeding habits of harp and hooded seals in drift ice waters along the east coast of Greenland in summer and winter. Polar Research 23: 35-42.
Haug, T., Nilssen, K. T., Lindblom, L. and Lindstrom, U. 2007. Diets of hooded seals (Cystophora cristata) in coastal waters and drift ice waters along the east coast of Greenland. Marine Biology Research 3: 123-133.
Hay, K., Stenson, G. B., Wakeham, D. and Myers, R. A. 1985. Estimation of pup production of hooded seals (Cystophora cristata) at Newfoundland during March 1085. Can. Atl. Fish. Sci. Adv. Comm.
International Council for Exploration of the Sea. 2006. Report of the ICES/NAFO Working Group on Harp and Hoodes Seals. ICES Advisory Committee on Fishery Management, Copenhagen, Denmark.
Johnston, D. W., Friedlaender, A. S., Torres, L. G. and Lavigne, D. M. 2005. Variation in sea ice cover on the east coast of Canada from1969 to 2002: climate variability and implications for harp and hooded seals. Climate Research 29: 209-222.
Kovacs, K. M. 1990. Mating strategies of male hooded seals (Cystophora cristata). Canadian Journal of Zoology 68: 2499-2502.
Kovacs, K. M. 2002. Hooded seal Cystophora cristata. In: W. F. Perrin, B. Wursig and J. G. M. Thewissen (eds), Encyclopedia of Marine Mammals, pp. 580-583. Academic Press, San Diego, California, USA.
Kovacs, K. M. and Lavigne, D. M. 1986. Cystopora cristata. Mammalian Species 258: 1-9.
Kovacs, K. M. and Lavigne, D. M. 1992. Mass transfer efficiency between hooded seal (Cystophora cristata) mothers and their pups in the Gulf of St. Lawrence. Canadian Journal of Zoology 70: 1315-1320.
Kovacs, K. M. and Lydersen, C. 2008. Climate change impacts on seals and whales in the North Atlantic Arctic and adjacent shelf seas. Science Progress 91(2): 117-150.
Kovacs, K. M., Lydersen, C., Hammill, M. O. and Lavigne, D. M. 1996. Reproductive effort of male hooded seals (Cystophora cristata). Canadian Journal of Zoology 74: 1521-1530.
Laidre, K.L., Stirling, I., Lowry, L.F., Wiig, Ø., Heide-Jørgensen, M.P. and Ferguson, S.H. 2008. Quantifying the sensitivity of Arctic marine mammals to climate-induced habitat change. Ecological Applications 18: S97-S125.
Lavigne, D. M. and Kovacs, K. M. 1988. Harps and hoods: ice-breeding seals of the northwest Atlantic. University of Waterloo Press, Ontario, Canada.
Learmonth, J. A., Macleod, C. D., Santos, M. B., Pierce, G. J., Crick, H. Q. P. and Robinson, R. A. 2006. Potential effects of climate change on marine mammals. Oceanography and Marine Biology: An Annual Review 44: 431-464.
Lucas, Z. and Daoust, P.-Y. 2002. Large increases of harp seals (Phoca groenlandica) and hooded seals (Cystophora cristata) on Sable Island, Nova Scotia, since 1995. Polar Biology 25: 562-568.
Lydersen, C., Kovacs, K. M. and Hammill, M. O. 1997. Energetics during nursing and early postweaning fasting in hooded seal (Cystophora cristata) pups from the Gulf of St Lawrence, Canada. Journal of Comparative Physiology B 167: 81-88.
Mignucci-Giannoni, A. A. and Haddow, P. 2002. Wandering hooded seals. Science 295: 627-628.
Øigård,T. A. and Haug, T. 2007. Estimating pup production of hooded seals in the Greenland Sea pack ice. In: J. Holmen, G. Gotaas and A. Johnsen (eds), Polar Research in Tromsø, pp. 4-5. Roals Amundsen Centre, Tromsø, Norway.
Øristland, T. and Øien, N. 1995. Aerial surveys of harp seal and hooded seal pups in the Greenland Sea pack ice. In: A.S. Blix, L. Walløe and Ø. Ulltang (eds), Whales, seal fish and man, pp. 77-87. Elsevier, Amserdam.
Pagnan, J. L. 2000. Arctic marine protection. Arctic 53: 469-476.
Reeves, R. R. and Ling, J. K. 1981. Hooded seal Cystophora cristata Erxleben, 1777. In: S. H. Ridgway and R. Harrison (eds), Handbook of marine mammals, Volume 2: seals, pp. 171-194. Academic Press.
Reeves, R.R., Stewart, B.S. and Leatherwood, S. 1992. The Sierra Club handbook of seals and sirenians. Sierra Club Books, San Diego, CA, USA.
Reijnders, P., Brasseur, S., van der Toorn, J., van der Wolf, P., Boyd, I., Harwood, J., Lavigne, D. and Lowry, L. 1993. Seals, fur seals, sea lions, and walrus. Status survey and conservation action plan. IUCN Seal Specialist Group.
Rice, D.W. 1998. Marine Mammals of the World. Systematics and Distribution. Society for Marine Mammalogy, Lawrence, Kansas.
Salberg A.-B., Haug, T. and Nilssen, K. T. 2008. Estimation of hooded seal (Cystophora cristata) pup production in the Greenlnad Sea pack ice during the 2005 whelping season. Polar Biology.
Sergeant, D. E. 1974. A rediscovered whelping population of hooded seals Cystophora cristata Erxleben and its possible relationship to other populations. Polarforschung 44: 1-7.
Sergeant, D. E. 1976. History and present status of populations of harp and hooded seals. Biological Conservation 10: 95-118.
St. Aubin, D. J. 1990. Physiologic and toxic effects on pinnipeds. In: J. R. Geraci and D. J. St. Aubin (eds), Sea mammals and oil: confronting the risks, pp. 103-127. Academic Press, New York, USA.
Stenson, G. B., Myers, R. A., Ni, I. H. and Warren, W. G. 1996. Pup production of hooded seals (Cystophora cristata) in the Northwest Atlantic. NAFO Sci. Coun. Studies 26: 105-114.
Sundt, R. C., Dahle, G. and Naevdal, G. 1994. Genetic-variation in the hooded seal, Cystophora cristata, based on enzyme polymorphism and multilocus DNA-fingerprinting. Hereditas 121: 147-155.
Tynan, C. T. and DeMaster, D. P. 1997. Observations and predictions of Arctic climate change potential effects of marine mammals. Arctic 50: 308-322.
Ulltang, Ø. and Øien, N. 1988. Bestandsutvikling ofg status for grønlands-sel og klappmyss (Population estimates and status of harp and hooded seals. In Norwegian). Fiskets Gantg 74: 8-10.
Waring, G. T., Josephson, E., Fairfield, C. P. and Maze-Foley, K. 2005. U.S. Atlantic and Gulf of Mexico marine mammal stock assessments – 2005. NOAA Technical Memorandum. NOAA.
Wiig, Ø. and Lie, R. W. 1984. An analysis of the morphological relationships between the hooded seals (Cystophora cristata) of Newfoundland, the Denmark Strait and Jan Mayen. Journal of Zoology (London) 203: 227-240.
Woodley, T. H. and Lavigne, D. M. 1991. Incidental capture of pinnipeds in commercial fishing gear. International Marine Mammal Association Technical Report 91-01: 35 pp.
|Citation:||Kovacs, K. (IUCN SSC Pinniped Specialist Group) 2008. Cystophora cristata. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 26 November 2014.|