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Sea Otter Savvy

Sea Otter Science And Community Outreach

The We Were Here sea otter program is dedicated to educating communities and stakeholders who are missing sea otters. 

 


What are we missing?

Have you ever wondered why you don’t see sea otters in San Francisco Bay or off the shores of northern California or Oregon? Truth is, sea otters did inhabit the San Francisco Bay, and their historical range once continued north along the Pacific coast to Alaska and over to Japan and Russia. In the early 1700s the worldwide sea otter population was estimated to be between 150,000 to 300,000 individuals. However, due to the maritime fur trade the sea otter population was decimated. By 1911, when sea otters were protected under the International Fur Seal Treaty, there were fewer than 2,000 individuals that remained across 13 different colonies. The continuous population was broken. Only one tiny remnant of the extensive population that existed between Alaska and Baja California, Mexico, survived, hidden off the Big Sur coastline. 

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    Our current population of southern (or California) sea otters is composed entirely of descendants from these few survivors. The southern sea otter is now recognized as a distinct subspecies from northern sea otters, though the former range of sea otters was most likely a latitudinal cline, with gradual differences in characteristics along the range that reflected local adaptations to temperature, available prey, or other relevant features of their environment. The sea otters most closely resembling today’s southern sea otters spanned from about mid-Oregon to Baja California. The current range of the southern sea otter, which stretches from Pigeon Point near Año Nuevo State Park down to Gaviota, near Santa Barbara, is still just a fraction of the historical range. Despite protections under the Endangered Species Act and the Marine Mammal Protection Act, the southern sea otter range has expanded slowly, and currently further expansion is met with challenges.

    For more detailed information on sea otter natural history and range click here

    To learn more about the history of sea otters in Oregon click here.

     

Why is range expansion so slow? After a population has been fragmented for so long, range recovery can be complex. Sea otter research and conservation began only in the mid to late 1900s. Our understanding of how coastal ecological communities changed with the removal of sea otters, and of how sea otters influence their ecosystem when they return, has developed over time through many studies. We have learned that female sea otters have small home ranges, with the costs and risks of motherhood keeping them close to familiar foraging areas. They also prefer areas with kelp (if on the outer coast) or eelgrass (if in estuaries), which provide protection from rough waves, strong currents, and potential predators. Kelp canopy in particular is thought to give sea otters some security from fatal bites by white sharks, the most significant cause of southern sea otter mortality. 
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    Unfortunately, since large stretches of the Pacific Coast are missing sea otters, the ecological balance has shifted, and both kelp and eelgrass habitats are at risk. Finally, because of the small home ranges of adult females, the shape of the coastline influences the speed of range expansion. Most of central California has a linear coastline, with only a narrow band of habitat in the depths usually used by sea otters (40 m, with most dives occurring in 25 m or less). This means that a large proportion of the population is in areas in the center of the range that have reached carrying capacity, whereas only a small proportion is at its edges, where abundant prey is available within feasible travel distance. In contrast, in areas like Southeast Alaska or British Columbia, which have convoluted coastlines with numerous with inlets, estuaries, islands, and fjords, or in areas like Washington, which has a broad, shallow coastal shelf, unoccupied habitat is available not just to the north and south of the occupied range, but also to the east and west. In these areas, the population can grow much more rapidly because sea otters can find unoccupied habitat, with abundant prey resources, within feasible travel distance in multiple directions. More food usually translates into faster population growth and range expansion. The combined effect of a linear coastline shape and high shark-bite mortality at the range peripheries, which are precisely the areas where rapid population growth would otherwise occur, is limiting how quickly the southern sea otter population can expand into new areas.

How might sea otters impact the San Francisco Bay Area, northern California, and other areas where they have been absent since the end of the maritime fur trade?

Sea otters are a keystone species, meaning they greatly influence their ecological community. Maintaining body temperature in the cold waters of the Pacific Ocean requires a high metabolism, and they must eat over ¼ of their body weight every day. This large appetite means they consume a lot of invertebrates (animals without backbones). Sea urchins and crabs are among their preferred prey items. When sea urchins become too abundant and begin to run out of food, they change their feeding behavior from a sit-and-wait strategy, where they subsist on drift kelp, to one in which they attack and eat kelp holdfasts, essentially clear-cutting kelp forests. Sea otters’ control of sea urchin populations enhances kelp abundance by preventing overgrazing.

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    In estuaries, sea otters enhance eelgrass by a slightly different mechanism. When crabs are overly abundant in estuaries, they eat too many mesograzers, like sea hares and isopods. These are the animals that clean epiphytes (fouling algae) off the eelgrass blades, allowing sunlight to penetrate. When sea otters control crabs in estuaries, they enhance eelgrass by allowing the mesograzers to keep the eelgrass blades clean. By helping kelp forests and eelgrass beds to thrive, sea otters indirectly provide sanctuary to hundreds of other species. They also indirectly help to slow climate change because kelp and seagrass remove carbon from the atmosphere and sequester some of it in the deep sea or in estuarine sediments. In addition to sequestering carbon, abundant kelp and eelgrass helps to mitigate some of the worsening consequences of climate change. It protects shorelines from erosion caused by intense storms and sea level rise and can locally reduce ocean acidification, which is especially damaging to calcareous (hard-shelled) species like shellfish.  You could say sea otters are ecosystem superheroes – promoting a diverse coastal community.

    If sea otters were to returnto northern California or beyond, they could potentially enhance eelgrass bed restoration in San Francisco Bay and assist with the restoration of kelp forests along the northern Pacific coast. Although sea otters do not eat starving sea urchins, they can help to defend recovering patches of kelp by eating healthy sea urchins at the margins. Those patches of kelp provide the spores for further kelp recovery. Because kelp and eelgrass provide habitat and food to so many other species, including species that are commercially or recreationally fished, the presence of sea otters can lead to healthier fisheries. Sea otters can impact the catch of some shellfish fisheries (such as abalone, red sea urchins, and crabs), but through their indirect effects they also help to ensure the availability of food or larval habitat for these species. Sea otters provide important economic and subsistence benefits to human communities through enhanced finfish fisheries, ecotourism, and carbon sequestration. Research in British Columbia showed that these combined economic benefits of sea otters outweighed the costs to shellfish fisheries by 7x. Often, however, those groups who gain from the presence of sea otters are different from those who incur losses. One important avenue of research is the development of economic mechanisms to ensure a fair distribution of costs and benefits if sea otters are proposed to be actively reintroduced.

Where would sea otters go?

Despite the limitations on range expansion, sea otters may still slowly extend their range naturally. In this case, for northern California, it is likely they would end up in San Francisco Bay and cross to Marin County in time. Where specifically they end up would depend on a balance of prey availability, habitat suitability, and type and magnitude of threats. If sea otters are considered for reintroduction, these locations would be extensively reviewed and chosen based on research that investigates habitat suitability, prey availability, risks from human impacts (pollution, boat traffic etc.), and impacts on human activities. You can learn about Dr. Brent Hughes research on how San Francisco Bay could increase the California sea otter population here.

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    Responding to a congressional mandate, the U.S. Fish and Wildlife Service is currently studying the feasibility and cost of reintroducing sea otters to the waters of the Pacific coast where they remain absent. The longest stretch of coastline where sea otters remain extirpated is between Point Grenville, Washington, where the northern subspecies was successfully reintroduced in the 1970s, and Pigeon Point in California, just south of San Francisco Bay, which marks the northern edge of the southern sea otter population. Oregon is the only Pacific coast state that still has no sea otters at all. As noted, above, evidence suggests the southern sea otter once ranged into the waters of the southern Oregon coast, and that Oregon served as an historical transition zone between southern and northern sea otters. You can read more about the current consideration of sea otter reintroductions to northern California and Oregon hereThe Elakha Alliance is a non-profit based in Oregon looking to reintroduce this once native keystone predator. You can review their recently published scientific based Feasibility Study Draft on the potential direct and indirect effects of relocating sea otters along the Oregon coast.

     


What can we do?

The best way to support sea otters is to remain informed on how the southern sea otter population is doing and to understand how you are a stakeholder in conversations about reintroduction even if you do not live on the coast or directly use marine environments or organisms. Consumptive value is just one kind of value. Other kinds of value are non-consumptive, such as benefits gained from carbon sequestration, which are ultimately experienced globally; benefits gained from recreating (boating, kayaking, surfing, paddleboarding, SCUBA diving, or watching and photographing wildlife) in flourishing marine ecosystems; or benefits gained from simply knowing that intact marine ecosystems exist.

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    Your awareness and understanding allows you to share this information with others and to use your voice. Sea otters, like other fish and wildlife populations in the United States, are held in public trust. This means the government manages and protects these resources to benefit the public (you). Therefore, your voice and opinions matter. The public will ultimately decide the fate of sea otters. 

    So, if you are wondering what you personally can do, you can: learn about sea otters, spread this knowledge with others, share your opinions with your representatives, and support research and conservation efforts.

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Thank you to all of our We Were Here partners and collaborators!