Sea otter, Enhydra lutris, containment management: field studies and feasibility assessment

Abstract

Limiting sea otter geographic distribution in California (containment management) has long been recognized as being necessary to preserve human recreational and commercial uses of shellfish resources. However, passage of federal legislation that focused preferentially on marine mammal protection and the 1977 listing of the California sea otter population as "threatened" effectively precluded any range-limiting management program. Research, however, that evaluated various non-lethal means of influencing sea otter movements and distribution was encouraged. Our research suggests that herding and acoustical devices may not have any real potential use in this context. Based on research-related capture success rates, capture and relocation techniques may be useful in influencing sea otter geographical distribution. The translocation of sea otters to San Nicolas Island provided the first opportunity to test the technical feasibility of maintaining a large area free of sea otters. Capture success rates were appreciably poorer than those achieved during research-related efforts. We identify several logistical and behavioral influences that contributed to the relatively poor success rate. Based on this evaluation, we discuss the factors likely to limit application of these techniques in the future. We feel that capture techniques can be useful in a long-term management program, if used in conjunction with efforts to limit the sea otter population growth rate. Consequently, we feel future research should focus on assessing individual health effects from using chemical contraceptives and assessing the feasibility of their use to safely control population growth. (12pp.)