The Dynamics of the Reproductive Characteristics of Northern Fur Seal (Callorhinus ursinus, Linnaeus, 1758) Females on Tyuleniy Island during Active Harvesting of Males

This paper analyzes the dynamics of reproductive characteristics of Northern fur seal females on Tyuleniy Island based on the data on their physiological state obtained by Japan and the USSR in the western part of the Pacific Ocean and the Sea of Okhotsk in 1958-1980. We have compared the dynamics of the reproductive characteristics of Northern fur seal females on Tyuleniy Island where commercial onshore harvesting of females was not practiced with those in the populations of the Pribilof Islands, where an experimental strategy of females harvesting was introduced, along with the commercial harvesting of males. Despite the significant difference in the harvesting strategies for fur seals from the Pribilof and Tyuleniy populations, an analysis revealed similar dynamics in the reproductive characteristics of females from both locations during the period of intensive hunting: a higher age at first birth and lower pregnancy rates of young females. The most likely reason for this negative trend in the population of Tyuleniy Island seems to be a shortage of young bulls and subadult males due to intensive hunting of males.