Changes in the abundance of sea lions worldwide is a concern to fisheries and conservation groups, in part because fisheries are feared to threaten sea lions and sea lions are feared to threaten fisheries. The September 2004 symposium, Sea Lions of the World, brought sea lion researchers together in Anchorage, Alaska. This proceedings book contributes to understanding why sea lion populations fluctuate, including Alaska's Steller sea lions. Interspecies comparisons shed light on why some populations decline while others increase, and insights are gained on whether trends in the abundance of sea lions are related to fishing activities through food dependencies or through conservation measures. Authors also discuss parasites, contaminants, nutrition, pup survival, foraging, wintering, historical fluctuations, and other topics.