Fur Seal Investigations, 1995

Counts of adult male northern fur seals (Callorhinus ursinus) are obtained each year on St. Paul Island and semi-annually on St. George Island as a factor of population monitoring. In 1995, counts were obtained from 11 to 16 July. A total of 5,154 harem and 8,459 idle adult male seals were counted on St. Paul Island. On St. George Island a total of 1,242 harem and 1,054 idle adult males were counted. Overall, these numbers represent a decrease of 13.2% in adult male seals on the Pribilof Islands since 1994. A similar pattern occurred between 1993 and 1994. Northern fur seal entanglement in marine debris has been studied cooperatively since the early 1980s by the National Marine Mammal Laboratory (NMML), the National Research Institute of Far Seas Fisheries of Japan, and the Aleut community of St. Paul Island. Studies conducted since 1988 indicate a decline in the rate of entanglement. There is variation in the degree of entanglement by debris type, seal age, and island. For instance, the 1995 rate of entanglement was significantly different among juvenile males on St. Paul (0.22%) and St. George Islands (0.39%), however there was no significant difference in adult male entanglement rates between the two islands. Differences are probably due to a higher incidence of entanglement in trawl net debris among juveniles on St. George Island. The overall rate of entanglement for all males was calculated as 0.18% and 0.22% for St. Paul and St. George Islands, respectively (Robson et al., this volume). Trends in the mass and length of fur seal pups serve as indicators of population health and have been monitored semi-annually since 1989. Consistent with earlier years, studies in 1995 demonstrated that male pups are heavier and longer on average than female pups, and pups tend to be both heavier and longer on St. George Island relative to St. Paul Island. The mean mass of