Sea Otter
History
of the Sea Otter
Sea otters have inhabited the northern coasts of the Pacific Ocean
since the Pleistocene, about 1 to 3 million years ago. By 1740, when
the Bering expedition explored the coasts of the Aleutian and Commander Islands,
there were between 100,000 and 300,000 sea otters on the Pacific coast
"Historical Range of Sea Otters".
Sea otter fur is extraordinarily dense, providing excellent insulation
in cold ocean waters. Their fur has up to 1 million hairs per square
inch, more than any other mammal. It is considered some of the finest
fur in the world. Native Americans on the Pacific coast hunted sea otters
throughout their range, but the abundant populations encountered by
early Russian hunters indicate that otters were not widely overhunted
before contact with Europeans. Between 1740 and 1900, Russian and American
fur traders harvested the sea otter almost to extinction in order to
profit from their fur.
By 1900 commercial harvest had essentially ceased for the simple reason
that it was difficult to locate a sea otter; they had been reduced to
13 tiny  remnant
populations totaling no more than a few hundred each "Remnant
Colonies". In 1911, the International Fur Seal Treaty halted
commercial hunting of sea otters.
Once commercial harvest ceased, sea otter populations rebounded and
re-colonized much of their former range between Prince William Sound;
Alaska west to the Kuril Islands. However, by the 1950s they became
extinct along the Pacific coast from Prince William Sound south to Baja
California, with the exception of one remnant population in California.
During the 1960s and 1970s, the Alaska Department of Fish and Game
reintroduced sea otters into former habitat in Alaska, Canada, Washington
and Oregon in collaboration with other State and 
Provincial wildlife management agencies. In 1987, otters were reintroduced
to San Nicholas Island in southern California. Due to these efforts,
sea otter populations in southeast Alaska, British Columbia and Washington
are currently stable or increasing. "Present
Distribution of Sea Otters"
Twentieth century human activity, especially coastal development and
marine pollution, provide the most recent threat to sea otter populations.
The most striking example was the Exxon Valdez oil spill in Prince William
Sound, Alaska. The oil tanker Exxon Valdez struck Bligh Reef on March
24, 1989, spilling 11 tons of crude oil into the Sound. 
According to surveys conducted by the U.S. Fish and Wildlife Service,
the spill killed approximately 3,905 sea otters (range 1,904-11,257).
At present, abundance of sea otters in some oiled areas of Prince William
Sound remains below pre-spill estimates, and evidence from ongoing studies
suggest that sea otters and the nearshore ecosystem have not fully recovered
from the spill.
For more
information on the Exxon Valdez oil spill and its effect on sea otters see Sea Otter Reports.
Recent precipitous declines in sea otter populations in southwest Alaska,
from Kodiak Island to the western Aleutian Islands, constitute the most
significant conservation issue for northern sea otters since commercial
fur trades. The reasons for the decline are unknown. The Service has
proposed this population for listing as Threatened under the Endangered
Species Act.
Other recent human threats to sea otter populations include contamination
from pollutants such as heavy metals or PCBs; pollutants from log transfer
sites and harbors; disturbance from recreational and industrial activity;
entanglement in fishing equipment, such as set nets or gill nets; competition
from commercial fishing for food; and fish offal dumped into marine
waters by seafood processing plants.
Last updated: December 5, 2008
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