The population of Steller sea lions (Eumetopias jubatus) in the western Aleutian Islands has declined significantly and is currently listed as an endangered species. Among the possible limiting factors for this population is predation by transient killer whales (Orcinus orca). The purpose of this report is to provide some analysis of the feasibility of limiting killer whale predation on Steller sea lions in the western Aleutian Islands using marine mammal deterrents. This report provides a review of various marine mammal deterrents, used primarily in fisheries, to either prevent marine mammal entanglement or predation. Deterrent methods are evaluated based upon various factors including effectiveness, particularly with killer whales, potential impacts on non-target species, including Steller sea lions, and feasibility of use in the western Aleutian Islands. Possible deterrent options are considered, however, all would require significant research before implementation. Based upon a thorough review of the literature, lack of previous long-term success and high degrees of uncertainty, it is unlikely that deterrents would be successful in this application.

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