U.S. Fish & Wildlife Service

Sea Otters

About the Species

The sea otter is the largest member of the weasel family and the smallest marine mammal.  Ninety percent of the world’s sea otters live in coastal Alaska.

The Marine Mammal Protection Act protects sea otters.  It prohibits commercial harvest of sea otters, and allows Alaska natives to hunt sea otters for subsistence and creation of handicrafts.

Sea otters were hunted nearly to extinction in the late 1700s and 1800s through commercial harvest for their luxurious furs.  Once commercial harvest ceased, sea otter numbers rebounded and they re-colonized much of their former range.

Sea Otters in capture pens
Sea Otters in capture pens. Credit: Verna Gill/Angela Doroff/USFWS

 

Sea otter ranges in Alaska
Sea Otter Range Map

Population

Sea otter numbers have declined in southwestern Alaska over the past 20 years.  Once containing more than half of the world’s sea otters, this population segment, which ranges from Kodiak Island through the western Aleutian Islands, has undergone an overall population decline of at least 55–67 percent since the mid-1980s.  In 2005, the U.S. Fish and Wildlife Service listed this distinct population segment as Threatened under the Endangered Species Act.  See the Sea Otters and the Endangered Species Act page for more details.

See Also

Sea otter floating on its back

FWS Role in Sea Otter Management

Marine Mammals Management biologists work to keep the Alaska sea otter population and its habitats healthy and ensure there will be opportunities for a variety of human uses, including subsistence hunting and wildlife viewing. 

  • We track sea otter population abundance, trends, and distribution throughout Alaska using aerial and boat-based surveys. Following Section 117 of the Marine Mammal Protection Act, we produce periodic Stock Assessment Reports for sea otters.  See our Reports tab below for information on stock assessments.
  • For the population stocks listed under the Endangered Species Act we produce recovery plans, determine critical habitat and review listing status. For more information
  • We provide pertinent information to the Service’s Endangered Species Office for Section 7 consultations.
  • We monitor health, disease, and patterns of mortality for sea otters in Alaska by; assessing information from ‘healthy’ live-captured animals, assessing information from stranded animals, and conducting forensic necropsies on dead sea otters.  Fore more information on some of our results see our Reports page
  • We work with the Alaska SeaLife Center and the Alaska volunteer stranding network to respond to all live stranded and dead sea otters where possible.  We assist in placing orphaned pups with approved aquariums i.e. see Oregon Coast Aquarium.
  • We use data from the Marking, Tagging and Reporting Program to assess harvest patterns of sea otters legally hunted by Alaska Native peoples.
  • We collaborate with research organizations. For example, we work to conduct research examining the impact of sea otter recolonization on commercial and subsistence fisheries in the Southeast Alaska population stock with the University of Alaska, the Alaska Sea Grant program and the North Pacific Research Board (for more information on this particular project) 
  • We present our latest research at scientific conferences and publish papers in peer-reviewed journals (see Reports page )
  • We work with graduate students, volunteers and interns on a variety of sea otter management and research projects.  For more information about these opportunities
  • We work with Alaska Native Organizations, for example, the Indigenous People’s Council on Marine Mammals, on issues of mutual concern and information sharing.  We engage in Government to Government consultations with Tribes.  For more information on Alaska Native relations.
  • We respond to pollution events, such as boat wrecks and oil spills that may threaten sea otters.
  • We provide comments on resource and conservation plans i.e. oil spill response planning documents and provide interagency reviews as well as testimony at public meetings.
  • We sit on expert panels to provide the most current information on sea otter management and research and provide peer reviews for reports and publications.
  • We review permits for the Service’s Division of Management Authority on requests to work with sea otters from researchers, photographers, documentary film makers, and aquariums.
  • We work with Industry (i.e. oil and gas exploration in Cook Inlet) to make sure development is not in violation of the Marine Mammal Protection Act and the Endangered Species Act.  We review applications for Incidental Harassment Authorization.
  • We conduct outreach and education about sea otters, their conservation, and the Marine Mammal Protection Act at many different venues i.e. schools, special events, Tribal and community meetings

Sea Otter Reports

To receive a copy of a publication or report listed here, please contact: 
Marine Mammals Management, U.S. Fish and Wildlife Service
1011 E. Tudor Road, Anchorage, Alaska 99503
or call 907-786-3800

Publications

2018

Garlich-Miller, J.L., G.G. Esslinger, and B.P. Weitzman. 2018. Aerial Surveys of Sea Otters (Enhydra lutris) in Lower Cook Inlet, Alaska, May 2017. U.S. Fish and Wildlife Service, Marine Mammals Management Technical Report: MMM 2018-01. 22pp. (pdf)  

2014

Burek, K.A., V.A. Gill, and D.S. Bradway.  2014.  The first case of locally acquired disseminated Histoplasmosis in Alaska and in a free-ranging marine mammal.  Journal of Wildlife Diseases 50(2): 389-392. DOI: 10.7589/2013-11-288 (pdf)

Carrasco, S.E., B.B. Chomel, V.A. Gill, A.M. Doroff, M.A. Miller, K.A. Burek, R.W. Kasten, B.A. Byrne, T. Goldstein, J.A.K. Mazet. 2014. Bartonella spp. Exposure in Northern and Southern Sea Otters in Alaska and California.  Journal of Vector-Borne and Zoonotic Diseases 14 (12): 831-837 (pdf)

Carrasco, S.E., B.B. Chomel, V.A. Gill, R.W. Kasten, R.G. Maggi, E.B. Breitschwerdt, B.A. Byrne, K.A. Burek-Huntington, M.A. Miller, T. Goldstein, J.A.K. Mazet.  2014.  Novel Bartonella Infection in Northern and Southern Sea Otters (Enhydra lutris kenyoni and Enhydra lutris nereis). Veterinary Microbiology 170: 325-334.  (pdf)

Marshall, C. D., K. Rozas, B. Kot, and V.A. Gill.  2014. Innervation Patterns of Sea Otter (Enhydra lutris) Mystacial Follicle-Sinus Complexes: Support For An Expanded Facial Somatosensory Cortex.  Frontiers in Neuroanatomy 8(121): 1-8.  DOI: 10.3389/fnana.2014.00121 (pdf)

Newsome, S.D. M.T Tinker, V.A. Gill, A.M. Doroff, L. Nichol, J. Bodkin (in press). The interaction of intraspecific competition and habitat on individual diet specialization:a near range-wide examination of sea otters.  Oecologia.

2013

Goertz C.E.C., R. Walton, N. Rouse, J. Belovarac, K. Burek-Huntington, V. Gill, R. Hobbs, C. Xavier, N. Garrett, and P. Tuomi. 2013. Vibrio parahaemolyticus, a Climate Change Indicator in Alaska Marine Mammals. In: F.J. Mueter, D.M.S. Dickson, H.P. Huntington, J.R. Irvine, E.A. Logerwell, S.A. MacLean, L.T. Quakenbush, and C. Rosa, eds. 2013. Responses of Arctic Marine Ecosystems to Climate Change. Alaska Sea Grant, University of Alaska Fairbanks. doi:10.4027/ramecc.2013.03 (pdf)

Larson, S.D., Z.N. Hoyt, G.L. Eckert, and V.A. Gill.  2013.  Impacts of sea otter predation on commercially important sea cucumbers (Parastichopus californicus) in Southeast Alaska.  Canadian Journal of Fisheries and Aquatic Sciences 70:1498-1507. (pdf)

2012

Counihan Edgar, K., V.A. Gill, A.M. Doroff, K.A. Burek Huntington, W. A. Miller, P.L.Shewmaker, S. Jang, E.C. Goertz, P.A. Tuomi, M.A. Miller, D. Jessup, and B.A. Byrne.  2012.  Genotypic Characterization of Streptococcus infantarius subspecies coli Isolates from Sea Otters with Infective Endocarditis and/or Septicemia and from Environmental Mussel Samples.  Journal of Clinical Microbiology 50(12):4131-4133. (pdf)

Tseng, M., M. Fleetwood, A. Reed, V.A. Gill, R.K. Harris, R.B. Moeller, T.P. Lipscomb, J.A.K. Mazet, and T. Goldstein. 2012. Mustelid Herpesvirus-2, a novel herpes infection in northern sea otters (Enhydra lutris kenyoni). Journal of Wildlife Diseases 
48:181-185. (pdf)

2011

Brownstein, D., M.A. Miller, S.C. Oates, B.A. Byrne, S. Jang, M.J. Murray, D.A. Jessup, and V.A. Gill. 2011. Antimicrobial susceptibility of bacterial isolates from sea otters (Enhydra lutris). Journal of Wildlife Diseases 47(2): 278-292. (pdf)

Goldstein, T., V.A. Gill, P. Tuomi, D. Monson, A. Burdin, P.A. Conrad, J.L Dunn, C. Field, C. Johnson, D.A. Jessup, J. Bodkin and A.M. Doroff. 2011. Assessment of clinical pathology and pathogen exposure in sea otters (Enhydra lutris) bordering the threatened population in Alaska. Journal of Wildlife Diseases 47(3): 579–592.(pdf)

2009

Goldstein, T., J.A.K. Mazet, V.A. Gill, A.M. Doroff, K.A. Burek, and J.A. Hammond. 2009. Phocine distemper virus in northern sea otters in the Pacific Ocean, Alaska, USA. Journal of Emerging Diseases 15(6): 925-927. (pdf)

Hart, K, V.A. Gill, and K. Kannan.  2009.  Temporal Trends (1992-2007) of Perfluorinated Chemicals (PFCs) in Northern Sea Otters (Enhydra lutris kenyoni) from South-central Alaska.  Archives of Environmental Contamination and Toxicology 56(3): 607-614. (pdf)

Von Biela, V.R., V.A. Gill, J.L. Bodkin, and J.M. Burns. 2009. Phenotypic plasticity in the average age of first reproduction in northern sea otters (Enhydra lutris kenyoni). Journal of Mammalogy 90(5):1224-1231 (pdf)

2008

Von Biela, V.R, W. J. Testa, V.A. Gill, and J. M. Burns. 2008. Evaluating cementum annuli to determine past reproduction in northern sea otters. Journal of Wildlife Management 72(3): 618-624. (pdf)

2005

Burn, D.M. and A.M. Doroff.  2005.  Decline in sea otter (Enhydra lutris) populations along the Alaska Peninsula, 1986-2001.  Fishery Bulletin 103:270-279. (pdf)

Estes, J.A., M.T. Tinker, A.M. Doroff, and D.M. Burn.  2005.  Continuing sea otter population declines in the Aleutian archipelago.  Marine Mammal Science.  21:169-172. (pdf)

2003

Burn, D.M., A.M. Doroff, M.T. Tinker. 2003. Estimated carrying capacity and pre-decline abundance of sea otters (Enhydra lutris kenyoni) in the Aleutian islands. Northwestern Naturalist. 84(3):145-148. (pdf)

Doroff, A.M., J.A. Estes, M.T. Tinker, D.M. Burn, and T.J. Evans. 2003. Sea otter population declines in the Aleutian archipelago. Journal of Mammalogy 84(1):55-64. (pdf)

2001

Gorbics, C.S. and J.L. Bodkin. 2001. Stock structure of sea otters (Enhydra lutris kenyoni) in Alaska. Marine Mammal Science 17(3): 632-647. (pdf)

1994

Burn, D.M. 1994. Boat-based population surveys of sea otters in Prince William Sound. Pp. 61-80 in: Marine Mammals and the Exxon Valdez. T. Loughlin (Ed.) Academic Press, Inc. (pdf)

DeGange, A.R., A.M. Doroff, and D.H. Monson. 1994. Experimental recovery of sea otter carcasses at Kodiak Island, Alaska, following the Exxon Valdez oil spill. Marine Mammal Science 10(4):492-496. (pdf)

Doroff, A.M. and J.L. Bodkin. 1994. Sea otter foraging behavior and hydrocarbon levels in prey following the Exxon Valdez oil spill in Prince William Sound, Alaska. In: Marine Mammals and Oiling. Ed. T.R. Loughlin. Academic Press.

Doroff, A.M. and A.R. DeGange. 1994. Sea otter prey composition and foraging success in the northern Kodiak archipelago. Fishery Bulletin 92:704-710 (1994).(pdf)

1993

Garrott, R.A., L.L. Eberhardt, and D.M. Burn. 1993. Mortality of sea otters in Prince William Sound following the Exxon Valdez oil spill. Marine Mammal Science. 9(4):343-359. (pdf - 928kb)

Technical Reports

2009

Gill, V.A., A.M. Doroff, and D. Burn. 2009. Aerial Surveys of Sea Otters Enhydra lutris in Kachemak, Alaska 2008. U.S. Fish and Wildlife Service report for Army Corps of Engineers. MIPR # WC1JUW80880784. 21pp. (pdf)

2007

Gill, V.A. and D. Burn. 2007. Aerial Surveys of Sea Otters Enhydra lutris in Yakutat Bay, Alaska 2005. U.S. Fish and Wildlife Service, Marine Mammals Management Technical Report: MMM 2007-01. 18pp. (pdf)

 Von Biela, V.R. and V.A. Gill. 2007. Analysis of the Sea Otter (Enhydra lutris) Reproductive Tract: A Methods Manual. U.S. Fish and Wildlife Service, Marine Mammals Management Technical Report: MMM 2007-02. 24pp. (pdf)

2006

Gill, V.A. 2006. Marine Mammal Unusual Mortality event initiation protocol for northern sea otters. Unpublished USFWS report. 11pp. (pdf)

2004

Burek, K.A. V.A. Gill, N. Bronson, and P. Tuomi.  2005.  A pictorial guide to sea otter anatomy and necropsy findings.  USFWS unpublished report.  44pp. (pdf)

2001

Ballachey, B.E., C.S. Gorbics, and A.M. Doroff. 2001. Sea otter mortality in Orca Inlet, Prince William Sound, Alaska, winter 1995-1996. U.S. Fish and Wildlife Service, Marine Mammals Management Technical Report: MMM 01-1. 23 pp.(pdf)

U.S. Fish and Wildlife Service. 2001a. Standard methods to assess over winter mortality trends in sea otter populations in Alaska. Marine Mammals Management, Anchorage, Alaska. 7 pp.

U.S. Fish and Wildlife Service. 2001b. Population trend surveys as an index to abundance and distribution of sea otters: a standard protocol in Alaska. Marine Mammals Management, Anchorage, Alaska. 10 pp.

1999

Doroff, A.M. and M. Roy. 1999. Sea Otter Surveys of Izembek Lagoon, Alaska: a Pilot Study. U.S. Fish and Wildlife Service, Marine Mammals Management, Anchorage, Alaska. 6 pp.

1997

Doroff, A.M. and C. Gorbics. 1997. Sea otter surveys of Yakutat Bay and adjacent Gulf of Alaska coastal areas - Cape Hinchinbrook to Cape Spencer 1995-1996. Final Report to Minerals Management Service. Interagency Agreement No. 05059. 23 pp. (pdf)

Doroff, A.M. and D. Mulcahy. 1997. A field guide to general necropsy and tissue collection for sea otters (Enhydra lutris) in Alaska. U.S. Fish and Wildlife Service, Marine Mammals Management Technical Report MMM 97-3. 49 pp.(pdf)

Evans, T.J., D.M. Burn, and A.R. DeGange. 1997. Distribution and relative abundance of sea otters in the Aleutian archipelago. U.S. Fish and Wildlife Service, Marine Mammals Management Technical Report MMM 97-5. (pdf)

1996

Doroff, A.M. and J.L. Bodkin. 1996. Sea otter foraging behavior and hydrocarbon levels in prey following the Exxon Valdez oil spill in Prince William Sound, Alaska. Exxon Valdez Oil Spill State/Federal Nat Natural Resources Damage Assessment Marine Mammal Study 6-8. Final Report. 33 pp. (pdf)

1995

Doroff, A.M. and A.R. DeGange. 1995. Experiments to determine drift patterns and rates of recovery of sea otter carcasses following the Exxon Valdez oil spill. Exxon Valdez Oil Spill State/Federal Natural Resources Damage Assessment Marine Mammal Study 6-9. Final Report. 13 pp. (pdf)

1994

U.S. Fish and Wildlife Service. 1994. Conservation plan for the sea otter in Alaska. Marine Mammals Management, Anchorage, Alaska. 44 pp.(pdf)

1993

Doroff, A.M., A.R. DeGange, C. Lensink, B.E. Ballachey, J.L. Bodkin, and D. Bruden. 1993. Recovery of sea otter carcasses following the Exxon Valdez oil spill. Pp. 285-288 in: Exxon Valdez Oil Spill Symposium, Program and Abstracts. 365 pp.