Northern sea otter, all 3 Alaska stocks Enhydra lutris (kenyoni)

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1 Northern sea otter, all 3 Alaska stocks Enhydra lutris (kenyoni) Conservation Status Heritage Agency G Rank: G4 USFWS/NOAA: S Rank: S4 SOA: Species of Greatest Conservation Need BLM: USFS: Class: Mammalia Order: Carnivora AA: IUCN: Endangered Final Rank Conservation category: IX. Blue IX = low status and low biological vulnerability and action need Category Range Status: -0 to Biological: -50 to Action: -40 to 40 - Higher numerical scores denote greater concern Status - variables measure the trend in a taxon s population status or distribution. Higher status scores denote taxa with known declining trends. Status scores range from -0 (increasing) to 0 (decreasing). Population Trend ( to 10) State short-term trend comments: Trends among three E. l. kenyoni stocks variable. Overall, Southeast Alaska stock is thought to be stable, Southcentral stock is stable, and the Southwest stock is declining rapidly. 3.6 The southwest Alaska stock has declined by more than 50% since the mid-1980s. In 005, the USFWS designated the southwest distinct population segment as threatened under the Endangered Species Act (ESA; USFWS 00b) due to an observed 70% population decline between 199 and 000 and an 88% decline at islands that were at carrying capacity in 1965 (USFWS 00b, Doroff et al. 004, USFWS 004c). The Southeast population increased from 8,807 in 1998 (USFWS 00b) to about 1,63 in 00 (USFWS 00b). Numbers in Glacier Bay were increasing rapidly, from 5 in 1995 to an estimated 1590 in 001, with an increase of 187% between 000 and 001 (Bodkin et al. 001). Although, trend for this stock has been one of growth and the Yakutat Bay population has increased over the last decade, the current trend for the entire stock is believed to be stable (USFWS 00b). The trend for the Southcentral population is uncertain, but it is thought to be stable. The 1989 Exxon Valdez oil spill in Prince William Sound resulted in an estimated mortality of 750-,650 otters. Since the spill, numbers in western Prince William Sound have increased by approximately 750 animals, but overall abundance in the sound has not increased appreciably since The lower current population estimate compared to the 00 stock assessment may be due to emigration from Orca Inlet into areas that have not been surveyed recently (USFWS 00b). Distribution Trend ( to 10) The historic range of the species is along the northern Pacific Rim, between central Baja CA and the islands of northern Japan. Beginning in about 1750, sea otters underwent dramatic declines as a direct result of commercial harvest for their furs. By 1890, the species had been eliminated throughout most of it's range, persisting at 13 locations in AK, Russia, and CA. Animals have been translocated from Amchitka Island and Prince William Sound to vacant habitat in SE AK, BC, and WA (Bodkin and Monson 003). Sea otters have expanded their range beyond the outer coast of southeast Alaska, and are currently occupying inside waters such as Glacier Bay and Sumner Strait. Although the southwest Alaska sea otter population is believed to have declined by more than 50% in the past 0 years, the overall range of the population has actually expanded slightly during the past 50 years (70 FR 46366). Status Total: 5.6 1

2 Biological - variables measure aspects of a taxon s distribution, abundance and life history. Higher biological scores suggest greater vulnerability to extirpation. Biological scores range from -50 (least vulnerable) to 50 (most vulnerable). Population Size ( to 10) Southwest Alaska stock: The most recent estimate is 53,674 based on surveys in and adjusted for animals not detected (USFWS 010d). Southeast Alaska stock: adjusted total estimate 10,563; minimum population estimate 9,136 based on surveys conducted in Southeast Alaska 00 and 003, Yakutat Bay 005, Glacier Bay in 00, and the Northern Gulf of Alaska 000 (USFWS 00b). Southcentral Alaska stock: adjusted total estimate 15,090 with a minimum of 1,774 individuals based on surveys conducted in the Northern Gulf of Alaska 1996, Prince William Sound 003, and Cook Inlet/Kenai Fjords National Park in 00 (USFWS 00b). Range Size ( to 10) Alaska range includes the Aleutian Islands, along the Alaska Peninsula, Kenai Peninsula and Prince William Sound, and southeastern Alaska. The range of the southeast stock extends from Dixon Entrance to Cape Yakataga; the southcentral stock extends from Cape Yakataga to Cook Inlet including Prince William Sound, the Kenai Peninsula coast, and Kachemak Bay; and the southwest stock includes the Alaska Peninsula and Bristol Bay coasts and the Aleutian, Barren, Kodiak, and Pribilof Islands. Distribution is continuous from Kachemak Bay to Cape Suckling; between Cape Suckling and Yakutat Bay there is 15 miles of vacant coastal habitat between southeast and southcentral Alaska stocks; nearly continuous distribution from Attu Island in the western Aleutians to the Alaska Peninsula (>00 km between some island groups) (USFWS 00b). Population Concentration ( to 10) Does not concentrate. Population is distributed throughout coastal waters of Alaska from the Aleutian Islands to southeastern with no focal aggregation sites. Reproductive Potential Age of First Reproduction (-5 to 5) Average age of sexual maturity for female sea otters is 3 to 4 years with some maturing at years of age (Rotterman and Simon-Jackson 1988). In Alaska, 30% of females were sexually mature at age, 100% by age 5; annual reproductive rates increased from % at age to 78% at age 5 and remained relatively stable (75-88%) through age 15 (Bodkin et al. 1993). Number of Young (-5 to 5) In California, adult females generally give birth to 1 pup every year. Ecological Specialization Dietary (-5 to 5) Feed on a wide variety of benthic invertebrates, including sea urchins, clams, mussels, crabs, and octopus. In some parts of Alaska, feed on epibenthic fishes (Estes et al. 198). Habitat (-5 to 5) Occupy nearly all coastal marine habitats, from fine sediment bays and estuaries to rocky shores exposed to oceanic swells. Habitat area depends on slope of the sea floor and where depth contour intervals are widely spaced, may extend far offshore to include shallow areas. Typically inhabit waters within 1 km of shore (Riedman and Estes 1990). Highest densities of sea otters occur in water less than 40 m deep where they have access to benthic foraging habitat in subtidal and intertidal zones (Reidman and Estes 1990), although they can be found in water up to 00 m deep (Bodkin and Udevitz 1999, Bodkin and Kenyon 004). Biological Total: Action - variables measure current state of knowledge or extent of conservation efforts directed toward a given taxon. Higher action scores denote greater information needs due of lack of knowledge or conservation action. Action scores range from -40 (lower needs) to 40 (greater needs). Management Needs ( to 10) -4 Sea otters are taken by Alaska Natives for subsistence purposes, and the harvest is currently not regulated in number or season but is reported low. Southwest stock listed as Threatened under the ESA and critical habitat designated. International Fur Seal Treaty of 1911 afforded sea otters protection from commercial harvest.

3 Monitoring Needs ( to 10) USFWS is responsible for the management and monitoring of this species. Although surveys are not conducted annually, they are conducted with some regularity and population estimates for all three stocks recognized in Alaska are available. Research Needs ( to 10) The leading hypothesis suggests that increased predation by killer whales (Orcinus orca) may be the cause of the sea otter decline in southwest Alaska. This hypothesis was arrived at largely through a "weight of evidence" approach. In southeast Alaska, growth limited by one or more of the following processes: reproduction, emigration, or mortality, with mortality the most likely factor. Possible factors contributing to morality include lack of food, pollution (or other habitat degradation), disease, predation, and human-caused mortality. Harvest levels in some regions of southeast may be sufficient to limit population growth (Esslinger and Bodkin 009). Cook Inlet oil and gas development may affect a small portion of sea otters in Alaska. Oil contamination affects insulative properties and buoyancy and impacts nearshore coastal habitats used by sea otters. Contaminants from other sources are of increasing concern. Alaska natives are legally allowed to take sea otters for subsistence or handicraft use. Mean annual reported subsistence take between 00 and 006 was 346 animals in southcentral, 91 in southwest, and 3 in Southeast. Occasionally taken incidentally in commercial fisheries. Sea otter strandings have occurred due to Streptococcus incatarius infection with the majority of cases occurring in Kachemak Bay (USFWS 00b). Survey Needs ( to 10) Habitat relationships are well described and range maps are currently available. Surveys (aerial and/ or boat) are established for all 3 stocks in Alaska (USFWS 00b). Action Total: - Supplemental Information Harvest: Seasonal Occurrence: Taxonomic Significance: Range Map - variables do not receive numerical scores. Instead, they that are used to sort taxa to answer specific biological or managerial questions. Not substantial Year-round % Global Range in Alaska: >10% % Global Population in Alaska: >5% Peripheral: Monotypic species No References 3

4 Bodkin, J. L. and K. W. Kenyon Sea otter. Pages in G.A. Feldham and B. Thompson, (eds) Wild Mammals of North America, nd Edition. Johns Hopkins University Press. Bodkin, J. L. and D. H. Monson Sea otter population structure and ecology on Alaska. Arctic Research of the United States16: Bodkin, J. L. and M. S. Udevitz An aerial survey method to estimate sea otter abundance. Pages 13-6 in G.W. Garner et al., editors. Marine Mammal Survey and Assessment Methods. Balekema, Rotterdam, Netherlands. Bodkin, J. L., D. Mulcahy, and C. J. Lensink Age-specific reproduction in female sea otters (Enhydra lutris) from south-central Alaska: analysis of reproductive tracts. Can. J. Zool. 71: Bodkin, J. L., K. A. Kloecker, G. G. Esslinger, D. H. Monson, J. D. DeGroot, and J. Doherty Sea otter studies in Glacier Bay National Park and Preserve. Annual Report 001. Burns, USFWS, personal communication Cronin, M. A., J. Bodkin, B. Ballachey, J. Estes, and J. C. Patton Mitochondrial-DNA variation among subspecies and populations of sea otters (Enhydra lutris). Journal of Mammalogy 77: Doroff, A. M., V. A. Gill, and J. A. Haddix Sea otter (Enhydra lutris kenyoni) surveys in the west and central islands of the Aleutian archipelago 003. Unpublished Report U.S. Fish and Wildlife Service Marine Mammals Management, MS 341. Esslinger, G. G. and J. L. Bodkin Status and trends of sea otter populations in southeast Alaska, U.S. Geological Survey Scientific Investigations Report p. Estes, J. A., R. J. Jameson, and E. B. Rhode Activity and prey selection in the sea otter: influence of population status on community structure. The American Naturalist 10: Federal Register. August 9, 005. Volume 7 (15): NatureServe NatureServe Explorer: An online encyclopedia of life. Version 5.0. NatureServe, Arlington, VA. Available Riedman, M. L. and J. A. Estes The sea otter Enhydra lutris: behavior, ecology, and natural history. Biological Report; 90 (14). U. S. Fish and Wildlife Service. Riedman, M. L., and J. A. Estes The sea otter (Enhydra lutris): Behavior, ecology, and natural history. Biological Report 90(14). U.S. Fish and Wildlife Service, Washington, DC. 16 p. Rotterman, L. M. and T. Simon-Jackson Sea Otter (Enhydra lutris). Pages In Selected marine mammals of Alaska: Species accounts with research and management recommendations (J.W. Lentfer, ed.). Marine Mammals Commission, Washington, D.C. U.S. Fish and Wildlife Service (USFWS). 00b. Stock assessment for Marine Mammals. Marine Mammal Protection Act Stock Assessment Report. Available online at: U.S. Fish and Wildlife Service (USFWS). 004c. Endangered and threatened wildlife and plants; listing the southwest Alaska distinct population segment of the northern sea otter (Enhydra lutris kenyoni) as threatened. Proposed Rules. February 11, 004, Fed U.S. Fish and Wildlife Service (USFWS). 010d. Southwest Alaska distinct population segment of the northern sea otter (Enhyra lutris kenyoni)- draft recovery plan. U.S. Fish and Wildlife Service, Region 7, Alaska. 171 pp. Wilson, D. E., et al Geographic variation in sea otters, Enhydra lutris. Journal of Mammalogy 7:-36. Version date: 1//013 Report authors: K. Walton, T. Gotthardt, and T. Fields 4

5 Alaska Natural Heritage Program University of Alaska Anchorage Anchorage, AK For details on the development of the ASRS and criteria, please see: Gotthardt, T. A., K. M. Walton, and T. L. Fields. 01. Setting Conservation Priorities for Alaska's Wildlife Action Plan. Alaska Natural Heritage Program, University of Alaska Anchorage, AK. 5