Washington State’s annual sea otter survey is now complete—and the Seattle Aquarium was an active participant. Our Curator of Conservation Research Shawn Larson recently shared some background on the species and how the survey works:
The history of the sea otter in Washington State is complex. We lost our last native sea otter in 1910; a victim of the maritime fur trade. The final pelt that was taken was sold by the hunter for $1,000, which at that time was enough to buy a house. That’s why sea otters were hunted to extinction: they were more valuable dead than alive.
In 1911, sea otters (along with other fur-bearing marine mammal species) were given protection from fur trade hunting under an international fur seal treaty. But Washington was without sea otters for over 60 years until, in 1969 and 1970, 59 otters were moved from Amchitka Island in Alaska to areas along the Washington coast near La Push. It’s thought that most of the translocated animals died—many animals were found washed ashore dead soon after. It’s estimated that the otters we see off the Washington coast today are descended from as few as 10 animals.
The transplanted sea otters were monitored sporadically for the first two decades after their introduction to Washington waters, but have been surveyed formally each year since 1989. The Aquarium has been involved since 2001. The annual survey occurs over one week in late June or early July and includes partners from many organizations.
The survey encompasses the entire Washington coast—from the Columbia River to the south, to the corner of northwest Washington near Tatoosh Island, and into the entrance to the Strait of Juan de Fuca to Neah Bay. Rafts (or groups) of sea otters are commonly found in rocky intertidal areas where kelp is growing and rocky reefs provide some protection for the waves.
The actual survey is conducted over three consecutive days, and involves counts taken from the ground as well as photos taken from an airplane. The reason for this is that counters on the ground are able to provide a more accurate count than the plane’s pictures, which often catch just the main raft of otters and miss outlying individuals as well as, sometimes, moms with small pups.
Five or six sites are selected each year; ground counters hike to their assigned sites and wait for the survey plane to fly over. When it does, the ground counters take their official count, noting the time and number of sea otter adults and pups. If conditions are good, the plane flies over twice each day.
The highest single-day count becomes the official count for that year, and reflects numbers from the plane’s photos as well as the ground counters. In 2014, we counted a high of 1,573 otters. The 2015 count won’t be finalized until later this year—it takes time to make the count from all the photos taken by plane.
Overall, the increase in the Washington sea otters since the annual counts began has been about eight percent per year—one of the highest growth rates for otters populations anywhere.