We in the Pacific Northwest are very lucky to have sea otters as offshore neighbors.
I decided to look into the history of sea otters offshore of Washington state, with an eye toward talking about how beneficial they are. Much to my surprise, their history is more dramatic than I ever imagined.
Sea otter population before the advent of fur traders in their territory is not known for sure but their numbers were once estimated at 150,000 to 300,000. They were hunted extensively for their fur from 1741 to 1911. A treaty was signed on July 7, 1911, that was designed to manage the commercial harvest of fur-bearing mammals (such as seals and sea otters) in the Pribilof Islands of the Bering Sea. This was the first international treaty to address wildlife preservation.
By this time, the world population of sea otters had fallen to 1,000 or 2,000 individuals, living in a fraction of their historic range. There were some left in Alaska but none south of that on the North American west coast.
Sea otters were reintroduced to our area in 1969 and 1970, when 59 animals were translocated from Alaska to two Washington sites. Nearly half of the otters released in 1969 died and those introduced in 1970 didn’t do so well, either. The current Washington sea otter population is descended from between 10 to 43 individuals that survived the two initial reintroductions. Some people estimate the number of survivors at about a dozen. We now have about 2000 that reside in Washington waters.
As marine mammals go, otters are rather small. Adult males weigh a bit under 70 pounds and females weigh in at about 50 pounds. They live from fifteen to twenty years. They have single births, which nearly always take place at sea. Cubs can be born in any season and are dependent on their mothers for about a year.
Otters are carnivores. They like to feed in around kelp stands. A typical diet includes crabs, clams, abalone, mussels, sea urchins, octopuses, and bottom fish such as lingcod. They consume a quarter of their body weight every day. This appetite for shell fish has brought them into conflict with coastal fishing folks.
On the other hand, the benefits of otters are the good they do for kelp stands. It all comes down to sea urchins. A number of creatures graze on kelp but the most destructive herbivore is the urchin. Over grazing by these little spiny beings is similar to over grazing by sheep or goats on land, They can clear out whole kelp forests. Otters really like to eat urchins. Otters equal fewer urchins equal more kelp equals more habitat for young food fish equals more income for fishers.
The University of British Columbia did a regional economic analysis of the costs and benefits of sea otter recovery along the west coast of Vancouver Island. This study showed that otters are excellent kelp farmers and the improved kelp stands led to increased supplies of food fish.
I personally think that anything as cute as otters doesn’t need to justify its existence by being useful but nature very seldom consults me. And yes, we are rather proud of our resident otters.