Collaborators: Lowell Fritz, National Marine Mammal Lab. Anne York, York Data Analysis.
From the mid-1970s through 2000, the western stock of Steller sea lion (Eumetopias jubatus) declined by over 80%. This fish- and squid-eating predator, the largest eared seal (Otariidae), is distributed across the North Pacific Ocean. The western stock breeds on rookeries west of 144°W in Alaska and Russia and the eastern stock breeds to the east and south to the Channel Islands off California. In 1997, the western stock of Steller sea lion was listed as endangered under the U.S. Endangered Species Act, which created new challenges for managers of Alaska’s groundfish fishery, the most productive in the United States. Since 2000, over $120 million, the largest budget for a U.S. endangered species, has been devoted to reducing uncertainty about the factors negatively affecting the population: food limitation, killer whale predation, disease, and direct or indirect impacts from fishing. But despite well-funded and large-scale coordinated research, the complexity, indirectness and cumulative effects of these factors have made it difficult to determine which were responsible for the decline and which are primary threats to recovery. This project is focused on using population models combined with data on the numbers and age distribution of Steller sea lions in the central Gulf of Alaska to estimate the historical changes in survivorship and fecundity that drove the decline.
Publications
Holmes, E. E. and A. E. York. 2003. Using age structure to detect impacts on threatened populations: a case study using Steller Sea Lions. Conservation Biology 17:1794-1806.
E. E. Holmes, L. W. Fritz, A. E. York and K. Sweeney. Fecundity declines in Steller sea lions suggest new conservation and research priorities. To be submitted.
Recent Meeting Presentations
EE Holmes, LW Fritz, AE York, & K Sweeney. Evidence of continuing declines in fecundity of Steller sea lions. Marine Mammal Society Meetings. San Diego, CA. December 2005. PDF of poster.
EE Holmes & AE York. Cooperative Fish and Wildlife Research Unit, WA Dept. of Fish and Wildlife, Invited speaker: "Monitoring the effect of management on long-lived species". Olympia, WA. December 2004.
EE Holmes & AE York. Society for Conservation Biology Annual Meeting, Invited speaker for Symposium on Designing Marine Reserves for Marine Mammals, "Using age-structure to monitor long-lived marine mammals" Hawaii. June 2001.
last modified
02/14/2007
Web site owner: Northwest Fisheries Science Center
From the mid-1970s through 2000, the western stock of Steller sea lion (Eumetopias jubatus) declined by over 80%. This fish- and squid-eating predator, the largest eared seal (Otariidae), is distributed across the North Pacific Ocean. The western stock breeds on rookeries west of 144°W in Alaska and Russia and the eastern stock breeds to the east and south to the Channel Islands off California. In 1997, the western stock of Steller sea lion was listed as endangered under the U.S. Endangered Species Act, which created new challenges for managers of Alaska’s groundfish fishery, the most productive in the United States. Since 2000, over $120 million, the largest budget for a U.S. endangered species, has been devoted to reducing uncertainty about the factors negatively affecting the population: food limitation, killer whale predation, disease, and direct or indirect impacts from fishing. But despite well-funded and large-scale coordinated research, the complexity, indirectness and cumulative effects of these factors have made it difficult to determine which were responsible for the decline and which are primary threats to recovery. This project is focused on using population models combined with data on the numbers and age distribution of Steller sea lions in the central Gulf of Alaska to estimate the historical changes in survivorship and fecundity that drove the decline.
