Sea otters have been absent from native habitats along the U.S. West Coast, including Northern California and Oregon, for more than 100 years. For years, tribes and stakeholders in Oregon have expressed interest and have been advocating for a sea otter reintroduction to the Oregon coast. To address these interests, I recently published a study, with Dr. Leigh Torres (Oregon State University) and Dr. Tim Tinker (University of California, Santa Cruz), estimating the carrying capacity of sea otters in Oregon (> 4,500 otters). Dr. Tinker, a co-author on this effort, published an earlier study, from which our Oregon analysis was based, predicting sea otter carrying capacity in California (> 17,000 otters). Together, these two studies suggest currently available habitats in Oregon and Northern California may support resident sea otter populations and sea otters could once again live in these historic habitats.
Sea otters are famed for their strong ecological role within kelp ecosystems; where via predation on herbivorous sea urchins, sea otters facilitate kelp growth uninhibited by intense urchin grazing. Oregon and California have, or are experiencing, kelp loss, partially due to unchecked sea urchin grazing. Another recent study suggests sea otters may play a role in reversing or preventing these declining trends by controlling urchin populations, but scientists and resource managers will need to carefully consider whether these habitats contain sufficient prey to sustain a viable sea otter population in the long run.
In January 2021, U.S. Congress approved a federal budget that included a directive to assess the feasibility of reintroducing sea otters along the U.S. West Coast. The Oregon and California carrying capacity estimates will greatly inform these sea otter reintroduction feasibility assessments for both Oregon and California. Whether sea otters may compete with fisheries for benthic invertebrates (e.g. abalone, red sea urchins), and balancing that with their role in future resilience to kelp loss, will likely be a focus of future discussions.
