Killer Whales and Predation on Steller Sea

The western stock of Steller sea lions has declined from over 140,000 individuals in the 1960s to possibly fewer than 40,000 individuals in 2000. The primary hypotheses put forth by the National Marine Fisheries Ser-vice (NMFS) explaining this decline centers around food limitation. One alternative hypothesis that has recently received attention is that the de-cline or lack of recovery is due to the effects of predation by killer whales or sharks. Reports of large numbers of killer whales surrounding longline and trawl fishing vessels in western Alaska suggest that there are many killer whales in the region. In order to assess the impact of killer whale predation on this popula-tion decline, we need the following information: 1. Number of Steller sea lions. 2. Intrinsic growth rate of Steller sea lion population. 3. Number of killer whales that prey on Steller sea lions. 4. Percentage of the killer whale diet that consists of Steller sea lions an