Hydrocarbon residues in sea otter tissues

On 24 March 1989, the T/V Exxon Valdez ran aground in Prince William Sound (PWS). eventually releasing 11 million gallons of Prudhoe Bay crude oil. The subsequent oil slick extended from PWS southwest along the Kenai Peninsula, past Kodiak Island to the Alaska Peninsula (Galt and Payton 1990). The spill encompassed extensive areas of sea otter (Enhydra lutris) habitat. Estimates of sea otter mortality due to the oil spill run between 3000 and 5000 animals, although only 878 carcasses were actually recovered (Bayha and Komendy 1990). Some of the recovered sea otters may have died quickly from hypothermia, or inhalation and ingestion of oil, while others may have survived for varying lengths of time before succumbing. An unknown and presumably very small number of animals may have died from causes unrelated to the oil spill and drifted into the oil slick to become coated with oil.

The effects of petroleum exposure on sea otters and other marine mammals have been reviewed (Geraci and Smith 1977: Geraci and St. Aubin 1980, 1990; Engelhardt 1983; Engelhardt 1985; Waldichuk 1990). However, very little has been published on the concentrations of hydrocarbons found naturally in marine mammal tissues or in animals exposed to oil.

We report the results of hydrocarbon analyses of tissues taken from ten sea otters found dead in western PWS following the Euon Valdez oil spill (EVOS). All of the carcasses were covered with oil when found. and evidence of the involvement of oiling in the deaths of these animals was provided by necropsy observations, However, the patterns of hydrocarbon prevalence and concentration varied among individual animals. We used those variations to divide the ten sea otters into three groups. In addition, we compare hydrocarbon residues in oiled sea otters to those in sea otters collected from an area in southeastern Alaska that has not experienced a crude oil spill.