Sea otters (Enhydra lutris) are the smallest marine mammal. This coastal marine
carnivore once ranged from northern Japan around the North Pacific Rim through
Russia, Alaska, Canada, and along the coast of the contiguous United States to central
Baja California in Mexico, perhaps numbering 300,000. However, the maritime fur trade in the late 18th and 19th centuries decimated sea otter populations throughout their
range, and they were exterminated in Japan. The North Pacific Fur Seal Treaty of
1911 enabled sea otters to recover and reoccupy historic habitat with varying levels of
success. Continued protection and conservation under U.S., Canadian and Russian laws will be required for many decades for sea otter populations to recover. As sea otters
return to Japan, it will be essential to quantify their effect on the coastal marine
ecosystem and to assess the socioeconomic costs and benefits of sea otter range
expansion to mitigate conflicts with commercially important fisheries.