Summary of female harp seal reproductive parameters
Two parameters, pregnancy rate and mean age of maturity, are of particular interest with respect to the management of Northwest Atlantic harp seals (Phoca groenlandicus) because they may be convenient indices of population change. In this study data are presented on mean age of sexual maturity (1980...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
1996
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.550.8122 http://archive.nafo.int/open/studies/s26/sjare2.pdf |
| Summary: | Two parameters, pregnancy rate and mean age of maturity, are of particular interest with respect to the management of Northwest Atlantic harp seals (Phoca groenlandicus) because they may be convenient indices of population change. In this study data are presented on mean age of sexual maturity (1980–92) and pregnancy rates (1980–94), and results are compared to the historical data base. Estimates of the total number of harp seals in the Northwest Atlantic declined from approximately 3.0 million in the 1950s to 1.8 million in the early 1970s and then increased steadily to 4.8 million seals by 1994. During this period, pregnancy rates increased from 85.5 % in the 1950s to 95.2 % in the mid 1960s and then declined steadily to 69.0 % in the early 1990's. The mean age of sexual maturity decreased from 5.8 years in the mid 1950s to 4.6 years in the early 1980s and then increased to 5.4 years in the early 1990s. Given the dynamics of the seal population, these variations in reproductive parameters, growth rates and body condition are consistent with a density-dependent reponse. Coinciding with the increase in seal abundance in recent years, there also has been changes in the availability of prey taken by seals – particularly capelin and Arctic cod. These changes could be related to the colder water temperatures observed since the mid 1980s. Key words: harp seals, reproduction, maturity NAFO Sci. Coun. Studies, 26: 41–46 |
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