Sea otter abundance, distribution, and pup production in Prince William Sound Alaska, following the Exxon Valdez oil spill

The authors investigated effects of the 1989 Exxon Valdez oil spill on the abundance, distribution, and pup production of sea otters (Enhydra lutris) in Prince William Sound by comparing counts made during 1990 and 1991 with prespill counts. Changes in the distribution of otters 1--2 years after the spill from that observed during the late 1970s and early 1980s were not related to oiled shorelines. Despite a substantial loss of sea otters immediately following the spill, the authors counted fewer otters than prespill investigators at only one of three heavily oiled islands, and from 1990 to 1991 their counts at this one site increased to a level equivalent to the latest (1985) prespill count. The unexpectedly high counts at two of the three oiled sites cannot be explained simply by interobserver variability between te pre- and postspill counts or by immigrations of otters from other parts of the sound. The most plausible explanation for the findings also involves a modest population increase prior to the spill. At three heavily oiled sites, pup production 1--2 years after the spill was as high as or higher than before the spill. These results indicate the potential for renewed population growth