CHANGES IN THE REPRODUCTIVE CHARACTERISTICS OF NORTHERN FUR SEAL FEMALES ON TYULENIY ISLAND DURING ACTIVE HARVESTING OF MALES

O.L. Zhdanova, A.E. Kuzin, Е.Ya. Frisman

Аннотация


Analyzing data on the physiological state of the northern fur seal females on Tyuleniy Island, which were captured at sea in the period of 1958–1980, we compare the trends with those observed in the populations of Pribylov Islands. Despite a significant difference in the fur seal harvesting strategies used for the Pribylov and Tyuleniy populations, the analysis revealed similar dynamics in the reproductive characteristics of females from both locations during the period of intensive hunting. There were a higher age of first birth and lower pregnancy rates of young females.


Ключевые слова


Callorhinus ursinus; northern fur seal; harvest; reproductive characteristics of females; age at first birth; proportion of pregnant females.

Литература


Zhdanova O.L., Kuzin A.E., Frisman E.Ya. Estimating the juvenile survival rate of male northern fur seals (Callorhinus ursinus): Mathematical modeling and data analysis. Matematicheskaya biologiya i bioinformatika, 2018, vol. 13, no. 2, pp. 360–375. DOI: 10.17537/2018.13.360 (In Russ.).

Frisman E.Ya., Zhdanova O.L., Kuzin A.E. The outcome of northern fur seal harvesting: the results of calibration of mathematical models based on observation data (the example of Tyulenii island population). Ekologiya, 2019, no. 2, pp. 149–160. (In Russ.).

Interim Convention on Conservation of North Pacific Fur Seals. 1957. Washington. Available at: http://sedac.ciesin.columbia.edu/entri/texts/acrc/1957FS.txt.html (accessed: 19.03.11)

Trites A.W., York A.E. Unexpected changes in reproductive rates and mean age at first birth during the decline of the Pribilof northern fur seal (Callorhinus ursinus). Canadian Journal of Fisheries and Aquatic Sciences, 1993, vol. 50, no. 4, pp. 858–864. DOI: 10.1139/f93-098


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