Abstract

Following passage of the Marine Mammal Protection Act of 1972, pinniped populations along the west coast of North America began to increase, many to the point of recovery or even localized overabundance. A case in point is the migratory male population of California sea lions (Zalophus californianus) in the lower Columbia River, where they frequently cause property damage and depredate catch in sport and commercial fisheries. In addition to these negative human interactions, California sea lions also prey heavily on several species of fish listed under the Endangered Species Act, a fact that led the states of Oregon, Washington, and Idaho to apply for and receive lethal removal authority for this species in 2008. State and federal biologists have sought to better understand and manage this situation by conducting basic and applied research when possible, and lethal and non-lethal management when necessary. Research tools include branding animals for lifelong identification, attaching telemetry transmitters for monitoring movements and behavior, tissue sampling for health screenings and disease monitoring, relocation to zoos and aquaria, and in limited circumstances chemical euthanasia.

Acknowledgments

The authors thank: Robert Stansell of the U.S. Army Corps of Engineers; Matt Tennis, Dan Heiner, and Dave Colpo of Pacific States Marine Fisheries Commission; Josh Oliver and Dyanna Lambourn of Washington Department of Fish and Wildlife; Julia Burco, DVM, and Bryan Wright of Oregon Department of Fish and Wildlife; Katherine Prager, DVM, of UC Davis; and the Oregon State University Veterinary Diagnostic Laboratory.