Sea otters historically ranged across the Pacific Rim from Baja California to northern Japan, and the California sea otter population at one time was estimated between 16,000-20,000. The fur trade of the 18 th and 19 th centuries caused sea otter populations to collapse, and by the early 1900s, the southern sea otter was believed to be extinct. In 1938, the public learned that a small remnant population of otters had been discovered living off the Big Sur coast. The population has slowly expanded, and since 1995, has fluctuated around 2,000 animals. The feeding habits of the sea otter have a top-down effect on the marine ecosystem, meaning that their actions affect organisms lower in the food chain.
Sea otters are also indicators of the health of that ecosystem.
The sea otter derives much of its nutritional needs from shellfish which, unfortunately, put the otter at odds with the commercial shellfish industry. However sea otters play an important role in maintaining the health of the kelp ecosystem. By limiting the numbers of shellfish that feed on kelp, the sea otter promotes the development of kelp forests which are larger, more productive, and more diverse biologically and structurally. Kelp beds, in turn, provide habitat for fish and other invertebrate species. Because these sea otters lived so close to oil tanker traffic, a major goal of the recovery plan was to minimize risk from any potential oil spills.