Sea otter mortality from the Exxon Valdez spill: Evaluation of an estimate from boat-based surveys

The Exxon Valadez oil spill killed large numbers of sea otters (Enhydra lutris) in Prince William Sound (PWS), Alaska, where the spill originated, as well as within the oil’s path along the coasts of the Kenai Peninsula and Kodiak Island. Sea otters attracted particular attention after the spill due to their public appeal (Batten 1990) and known vulnerability to oil (Costa and Kooyman 1982, Siniff et al. 1982, Davis et al. 1988, Williams et al. 1988). Extensive efforts were made to rescue and rehabilitate oiled otters at a resulting cost of ca. \$80,000 per animal (Estes 1991). The argument that otters lost in the spill should be similarly valued made the estimate of mortality a matter of substantial concern to those involved in spill-related litigation or out-of-court settlements.