Reproductive rates of ringed seals and survival of pups in Northwestern Hudson Bay, Canada, 1991-2000

摘要

Reproductive parameters were determined from a sample of ringed seals collected by Inuit hunters during their annual open water harvest in autumn at Arviat, Nunavut, on the western coast of Hudson Bay, Canada, in 1991-1992 and 1998-2000. Ovulation rates of adult females were high and similar to rates recorded from studies of ringed seals in other geographic areas. However, pregnancy rates averaged only 55% and were significantly lower than in other studies, and the proportions of young-of-the-year were only 4.8, 4.2, 7.5, 4.1, and 23% for the mentioned years, respectively, instead of being > 30% as expected. These results appear to indicate that reproductive parameters of ringed seals and survival of their young are exhibiting long-term shifts rather than short-term fluctuations, and that the trend is downward. Furthermore, these downward trends in reproduction, in conjunction with changes in the proportions of different seal species in the diet of polar bears, climatic warming in western Hudson Bay, and progressively earlier breakup of sea ice over the last 25-years, suggest that major changes are occurring in the marine ecosystem of Hudson Bay. The pathways involved are poorly understood and merit further study.