Failure of reproduction in ringed seals (<i>Phoca hispida</i>) in Amundsen Gulf, Northwest Territories in 1984-1987

Abstract

Ringed seals (Phoca hispida) in Thesiger Bay (about 71 °45'N, 125°00'W), in northwestern Amundsen Gulf in the western Canadian Arctic, suffered a failure of pup production in the years before 1987, starting probably in 1984. Pups taken in the summer hunt in the years before 1987 were reported scarce, and in 1987 were only 2.8% of the total 4+ and older. This low reproduction was associated with poor body condition in females and with an age distribution of adults that was weighted toward older animals (the modal year class was the 8+ class). An unusually high proportion of adult females had never reproduced; the median age of first birth was estimated at 8.6 years. By the summer of 1988 the age distribution had changed toward younger animals (modal age 5+), in better condition (by 20%), which had almost all ovulated. Pups were more numerous in the catch. In 1989 pups were very numerous in the catch (142% of the 4+ adults) and the estimated mean ageof first birth had decreased to 5.3 years; almost all 5-year-olds sampled had borne pups. A similar occurrence of low pup production had been documented in the early 1970s, and resumption of reproductive activity had then also been associated with an apparent turnover of the population, the mean age of adults decreasing from 16-17 years when reproduction was low to 10.9 years in the year before reproduction resumed. Long-term data on ringed seals in the western Canadian Arctic has shown an average age at first ovulation of about 5.55 years and first birth just before age 7, about 1 year older than seen in this sample in 1989. Our 1989 sample may have been able to mature earlier because food was temporarily more abundant, or breeding densities temporarily lower, than long-term average values.

Variation in Reproduction and Body Condition of the Ringed Seal (<i>Phoca hispida</i>) in Western Prince Albert Sound, NT, Canada, as Assessed Through a Harvest-based Sampling Program

“…This fact obviates comparison with the values calculated by Smith (1987) or those available from other studies (i.e., Kingsley and Byers, 1998).…”

“…Changes documented in the seal population of the western Artic have included reductions in ovulation rates among mature females, the percentage of pups in the harvest (Smith, 1987), and the number of birth lairs (Smith and Stirling, 1978); a possible shift in the age of sexual maturity (Kingsley and Byers, 1998); and changes in relative abundance during both ice-covered (Stirling et al, 1977) and open water (Harwood and Stirling, 1992) periods.…”

Quantifying the Sensitivity of Arctic Marine Mammals to Climate-Induced Habitat Change

“…In the mid-1960s, 1970s, and 1980s, reproductive failures in ringed seals in the Beaufort Sea and Amundsen Gulf were associated with severe ice conditions (Stirling and Archibald 1977, Smith and Stirling 1978, Stirling et al 1982, Smith 1987, Kingsley and Byers 1998, Stirling 2002. It took approximately three years before reproduction and pup survival returned to normal, and immigration may have been partially responsible for the recovery in total numbers.…”

“…Stirling (2002) reviewed studies of large-scale declines in ringed seal and polar bear reproduction and survival of young in both the mid-1970s and mid-1980s in the southeastern Beaufort Sea. Reduced reproductive rates or lack of reproduction in ringed seals were associated with heavy overwinter sea ice conditions, late breakup, and probably reduced primary and secondary productivity (Smith and Stirling 1978, Stirling et al 1982, Kingsley and Byers 1998 and demonstrated that environmental fluctuations were capable of having a significant influence on reproductive success.…”

An Emerging Pattern of Declining Growth Rates in Belugas of the Beaufort Sea: 1989–2008

“…They respond to ecosystem variation with changes in body condition, which is directly linked to the year-to-year availability and quality of their prey. Changes in condition can eventually affect reproduction, growth rates, and survival of individuals, all of which can have impacts on populations (Smith, 1987;Kingsley and Byers, 1998;Stirling, 2002;Moore, 2008;Williams et al, 2013).…”