California sea otters

Information on the size, distribution, and productivity of the California sea otter population is broadly relevant to two federally mandated goals: removing the population’s listing as threatened under the Endangered Species Act (ESA) and obtaining an “optimal sustainable population” under the Marine Mammal Protection Act.  Except for the population in central California, sea otters (Enhydra lutris) were hunted to extinction between Prince William Sound, Alaska, and Baja California (Kenyon 1969). Wilson et al. (1991), based on variations in cranial morphology, recently assigned sub-specific status (E. l. nereis) to the California sea otter. Furthermore, mitochondrial DNA analysis has revealed genetic differences among populations in California, Alaska, and Asia (NBS, unpublished data).

In 1977, the California sea otter was listed as threatened under the ESA, largely because of its small population size and perceived risks from such factors as human disturbance, competition with fisheries, and pollution. Because of unique threats and growth characteristics, the California population is treated separately from sea otter populations elsewhere in the North Pacific.