A new way to estimate the age of bowhead whales (Balaena mysticetus) using ovarian corpora counts
Abstract:We used lengths and reproductive data for bowhead whales (Balaena mysticetus L., 1758) harvested by Alaskan Eskimos to estimate female reproductive parameters and age. Data from 117 females determined that 75 were sexually mature and 42 were immature. Estimated length at sexual maturity was 13.35 m. Counts of ovarian corpora were obtained from 50 mature females. Corpora and baleen data were used with aspartic acid racemization (AAR) data to obtain estimated age at sexual maturity (ASM) at ≈26 years. The number of corpora counted in both ovaries (or estimated when only one ovary was counted) was used with ASM and estimated ovulation rate (OR) to obtain corpora age estimates ranging from 26 to 149 years. A stone harpoon tip recovered from whale 92B2 was consistent with her corpora age of 133 years. The correlation between corpora and AAR age estimates was 0.77. Estimated standard errors of corpora ages tended to be somewhat higher than those for comparable AAR ages. A sample of potentially mature females examined for maturity and presence of a corpus luteum and (or) fetus provided an OR value of 0.332·year–1 and an estimated pregnancy rate of 0.326·year–1, implying intervals between ovulations and pregnancies of 3.0 and 3.1 years.
Document Type: Research Article
Affiliations: 1: North Slope Borough, Department of Wildlife Management, P.O. Box 69, Barrow, AK 99723, USA. 2: Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775-7000, USA. 3: Department of Statistics, University of Washington, P.O. Box 354322, Seattle, WA 98195-4322, USA. 4: School of Arts and Sciences, University of Alaska Southeast, 11120 Glacier Hwy (SOB1), Juneau, AK 99801, USA. 5: Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843, USA. 6: School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, P.O. Box 757220, AK 99775-7220, USA.
Publication date: September 24, 2011
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