COMPARATIVE POPULATION-DYNAMICS OF FUR SEALS

The population sizes, trends, exploitation, and life history parameter s for the ten fur seal species and subspecies are summarized. The larg est population is that of Arctocephalus pusillus pusillus with approxi mately two million seals, and the smallest is A, townsendi with approx imately 7,000 individuals. Most populations are legally protected, alt hough controlled harvesting may occur. None of the fur seal population s is currently known to be decreasing. Data are presented for paramete rs related to the survival of pups, juveniles, adults, and territorial males, and to reproduction, including the age of attainment of territ orial status, aggregation sizes, age of first parturition, pregnancy r ates, sex ratios of young animals, and information on the birth season s of the different species. Since pinnipeds are often of concern in fi sheries management, their daily consumption rates are of importance, a nd consequently data on body masses are summarized and the paucity of data on consumption rates as a function of body mass noted. A simplifi ed age-structured model is developed, and the results of this model ar e compared with results from more detailed models based on two publish ed life tables for Callorhinus ursinus. This comparison shows that the use of the simplified age-structured model is justified to explore ch anges in population growth rate. However, the simplified model does sh ow exaggerated age structure effects compared to the more detailed mod els. This model is used to compare the population dynamics of those sp ecies for which sufficient data are available. Areas in which limited, or no, data are available for the different fur seal species are high lighted.