The California sea lion (Zalophus californianus) is the most abundant pinniped in northwestern Mexico. Five cohorts at the breeding colony on a small island (Los Islotes) in the Gulf of California were tagged and monitored over their lifespan to create data for demographic modeling. Changes in demographic characteristics from 1979 through 2004 were analyzed. Estimates of growth rate, length-weight relationships, and mortality coefficient per age and sex groups are provided. A 25-year simulation period showed a deficit in the number of pups with respect to adult females arriving at the colony. This analysis of the population dynamics provides an accuracy that was not possible in previous studies.

Gulf of California, pinniped, population dynamics, sea lion, Zalophus californianus, breeding colony.