Abstract
A nine-winter-long study (1983-91) of marine mammals at Santa Cat- <br /><br />alina Island, California provided data on the ecological relationships among three <br /><br />pinniped and nine cetacean species observed there. A dramatic reduction in the <br /><br />number of California sea lions occurred during and following the winter with the <br /><br />most severe effects from the 1983 El Nino. The most striking change in cetacean <br /><br />occurrence was a precipitous decline in pilot whale numbers followed by an <br /><br />increase in abundance of Risso's dolphins. The six most often-sighted cetaceans <br /><br />appeared to partition the habitat according to water depth and distance from <br /><br />shore.
