Conservation

(Image credit: © Camille Pagniello, 2017)

(Image credit: Larson et al., 2021)

(Image credit: Mysid, 2006)

Current and historical distribution

Historically, the sea otter was found in a wide range across the East coast of North America, heading west across the coast of Alaska and reaching far out across the Pacific into Japan and Russia. Currently, the species has been extirpated from many regions, especially in the continental United States such as Oregon. Conservation efforts are constantly being reworked and introduced in different regions to help increase genetic diversity. The reason that this work is necessary is due to the Maritime Fur Trade, when the sea otters were hunted to near-extinction, triggering the genetic bottleneck effect (Larson et al., 2021).

The bottleneck effect is when the genetic diversity (the variety of alleles and genes seen within the species) of a population is greatly reduced due to a catastrophic event leaving very few survivors and therefore very little diversity. The genes of the survivors become the genes of the entire population, and the genetic structure of the population may be drastically different than it was before the catastrophe (Fowler et al., 2017). Thanks to conservation efforts, Southeast Alaska's genetic diversity is the greatest of all sea otter populations, at 78% diversity of what it was pre-bottleneck (Larson et al., 2021).

Enhydra lutris is listed as endangered under the IUCN Red List as of its most recent assessment on the 21st of January 2020 (Doroff et all., 2021). The species is currently on the Convention on International Trade in Endangered Species of Wild Fauna and Flora's (CITES) Appendix I, being the appendix with the most critical endangered species. Being on this list internationally prohibits the commercial trade of this species, which is vital protection given the highly desirable nature of its pelt (CITES 2022). The Marine Mammal Protection Act of 1972 and the Endangered Species Act 1973 apply protections specifically in the United States while making exceptions for sustainable, traditional indigenous practices. The U.S Fish and Wildlife Service is responsible for the conversation and management of the species in the United States (Doroff et al., 2021).

(Image credit: USFWS, 2007)

Population Demographics & Decline

There are many factors weighing in to why the species is still in decline despite both the end of the Maritime Fur Trade and a surge in conservation efforts. Despite their historical numbers reaching 300,000, the current population estimate is less than 130,000 (MMC, 2022). The species is extremely vulnerable to oil spills, a huge hazard to sea otter health and a major factor in this decline. As you may recall, sea otters are one of the few marine mammals to rely on fur rather than blubber to keep warming in the freezing ocean. Oil penetrates their water-proof fur and the air trapped under their fur to keep them warm escapes; this quickly causes them to perish from hypothermia (Costa & Kooyman, 1982). Increased orca predation is another big player in the continued decline of sea otter populations, which is covered more in depth on the ecology page under "species interactions."

Sea otters are considered a sentinel species (Jessup et al., 2004). A sentinel species is a species whose status can indicate the status of the ecosystem. The "canary in the coal mine" is a classic example, miners would take canaries into coalmines because of their sensitive respiratory systems, if toxic gasses were present, they would fall ill and cease singing, indicating danger to the miners and giving time to evacuate before the toxicity affects them (NRC, 1991). When environmental issues arise, looking to the status of the sea otters can determine if there are problems as they are extremely vulnerable to marine pollutants such as petroleum and the animals they prey on store high concentrations of the present toxins in the water, making them ill (Jessup et al., 2004).

While sea otters have made a remarkable comeback since their near-extinction in 1911, they still face a variety of threats. These include disease, oil spills (as described above), predation (as described on the ecology page), entanglements in fishing gear, and poaching (MMC, 2022).

Mediating Decline

What can be done?

While the Marine Mammal Protection Act of 1972 did much to halt the over-hunting of sea otters, there is more that can be done. Given that oil spills are one of the biggest problems facing otter populations, offshore drilling is something that needs to be stopped. Call your local representatives, senators, and governor and ask them to protect our environment and stop offshore drilling. The Chesapeake Bay Foundation, the Natural Resources Defense Council, Ocean Conservation Reasearch all have campaigns against offshore drilling that can be supported here, here, and here. Other conservation efforts include protecting the health of the kelp forests, better regulation by the U.S Department of Fish and Wildlife Service of commercial fishing practices and further study of the effects of toxic algae blooms on sea otter mortality (MMC 2022).

Why should we make the effort?

There are currently more than 41,000 species on the IUCN Red List that are under threat of extinction (IUCN 2022). What is so special about this one? The sea otter is a keystone species. This means that the effect of these animals is disproportionately large relative to the abundance of the species. We've witnessed this before. When they were overhunted for fur, their population was extirpated from certain kelp forest ecosystems (Davic, 2003). As the main predator of sea urchins, when the otters vanished they overpopulated and quickly took over these ecosystems. This wreaked havoc on the entire ecosystem; the kelp that built the ecosystem was replaced by "urchin barrens" (Stewart & Konar, 2012). Thousands of marine organisms rely on the kelp forests to survive. Kelp is a food source and shelter for many animals and absorbs large quantities of carbon dioxide. When the animals that hide in kelp have no kelp to hide in, they are exposed and killed. When the animals that eat the kelp have no kelp to consume, they die (Power et al., 1996). The predators of said animals, such as bald eagles, have a huge loss in the abundance of prey available and also go hungry. The ecosystem collapses, this is called trophic cascade (Anthony et al., 2008). The existence of countless other species rely on the continued existence of the sea otter. This marine mammal may be small, but the effects it has are huge.

References:

Larson, S., Gagne, R. B., Bodkin, J., Murray, M. J., Ralls, K., Bowen, L., Leblois, R., Piry, S., Penedo, M. C., Tinker, M. T., & Ernest, H. B. (2021). Translocations maintain genetic diversity and increase connectivity in sea otters, Enhydra lutris. Marine Mammal Science, 37(4), 1475–1497. https://doi.org/10.1111/mms.12841

Fowler, S., Roush, R., & Wise, J. (2017). Concepts of Biology. openstax.org. OpenStax. Retrieved December 15, 2022, from http://cnx.org/contents/b3c1e1d2-839c-42b0-a314-e119a8aafbdd@13.11.

Doroff, A., Burdin, A. & Larson, S. 2021. Enhydra lutris (errata version published in 2022). The IUCN Red List of Threatened Species 2021: e.T7750A219377647. https://dx.doi.org/10.2305/IUCN.UK.2021-3.RLTS.T7750A219377647.en. Accessed on 16 December 2022.

UNEP. (2022, June 22). Appendices. CITES. Retrieved December 16, 2022, from https://cites.org/eng/app/appendices.php

Mysid (2006). CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons

USFWS. (2007). Sea Otter. flickr.com. Flickr. Retrieved from https://flic.kr/p/aJ7Yvz.

Costa, D. P., & Kooyman, G. L. (1982). Oxygen consumption, thermoregulation, and the effect of fur oiling and washing on the sea otter, enhydra lutris. Canadian Journal of Zoology, 60(11), 2761–2767. https://doi.org/10.1139/z82-354

Jessup, D. A., Miller, M., Ames, J., Harris, M., Kreuder, C., Conrad, P. A., & Mazet, J. A. K. (2004). Southern Sea Otter as a Sentinel of Marine Ecosystem Health. EcoHealth, 1(3). https://doi.org/10.1007/s10393-004-0093-7

National Research Council (US) Committee on Animals as Monitors of Environmental Hazards. Animals as Sentinels of Environmental Health Hazards. Washington (DC): National Academies Press (US); 1991. PMID: 25144054.

U.S Government. (2022, November 2). Sea otters - marine mammal commission. Marine Mammal Commission. Retrieved December 18, 2022, from https://www.mmc.gov/wp-content/uploads/Sea-Otter-session_brief-summary1.pdf

Davic, R. D. 2003. Linking keystone species and functional groups: a new operational definition of the keystone species concept. Conservation Ecology 7(1): r11. [online] URL: http://www.consecol.org/vol7/iss1/resp11/

Stewart, N. L., & Konar, B. (2012). Kelp forests versus Urchin Barrens: Alternate stable states and their effect on sea otter prey quality in the Aleutian Islands. Journal of Marine Biology, 2012, 1–12. https://doi.org/10.1155/2012/492308

IUCN. 2022. The IUCN Red List of Threatened Species. Version 2022-1. https://www.iucnredlist.org. Accessed on 19 November 2022.

Mary E. Power, David Tilman, James A. Estes, Bruce A. Menge, William J. Bond, L. Scott Mills, Gretchen Daily, Juan Carlos Castilla, Jane Lubchenco, Robert T. Paine, Challenges in the Quest for Keystones: Identifying keystone species is difficult—but essential to understanding how loss of species will affect ecosystems, BioScience, Volume 46, Issue 8, September 1996, Pages 609–620, https://doi.org/10.2307/1312990

Pagniello, C. (2017). Fish Sounds - Kelp Forest. Flickr. California Sea Grant. Retrieved December 19, 2022, from https://www.flickr.com/photos/caseagrant/46267906622/in/photolist-2dux7FY-2bLRiR-kvc4HZ-sHZBC6-2kCvfhP-6MPTiu-2kZye13-2ct4GpG-nxnV8N-6PHW8i-2kDqTRG-2k66YB3-2k66YHW-4Xq9aH-2k66YSt-dbt7AP-8PjnfG-GoKvdb-othVk1-2k66m1S-2ii1xn-q59DvY-wSGvKf-knXvp-89mGmH-25p7dfr-4B57mx-24o5kaM-GRY3at-2fzJQ1-aVoVGr-g2ntEW-2jivZEj-a2LWaB-a2LVWn-om1qps-xz1Qzs-ahEJ3b-6pnsn-xSgAFB-21C9JPS-2k62xGN-weiuqi-6peSN-6pebX-Gvhxf-22TPkxM-6peSM-a2LiHM-okQxHN.

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