We use age distributions of sea otters (Enhydra lutris) found dead on beaches of western Prince William Sound, Alaska, between 1976 and 1998 in conjunction with time-varying demographic models to test for lingering effects from the 1989 Exxon Valdez oil spill. Our results show that sea otters in this area had decreased survival rates in the years following the spill and that the effects of the spill on annual survival increased rather than dissipated for older animals. Otters born after the 1989 spill were affected less than those alive in March 1989, but do show continuing negative effects through 1998. Population-wide effects of the spill appear to have slowly dissipated through time, due largely to the loss of cohorts alive during the spill. Our results demonstrate that the difficult-to-detect long-term impacts of environmental disasters may still be highly significant and can be rigorously analyzed by using a combination of population data, modeling techniques, and statistical analyses.
According to the work of Rausch (1953) , two species of helminth parasites, Porrocaecum decipiens (Krabbe, 1878) and Microphallus pirum (Afanas'ev, 1941), are pathogenic for the sea otter, Enhydra lutris (L.) , on the Aleutian Island of Amchitka. In continuation of investigations of sea otter mortality on Amchitka during the latter part of May and early June, 1952, the writer made an attempt to
obtain information on the life cycles and developmental characteristics of these parasites. It is the purpose of this paper to report the results of these observations.