Arctic | Mammals
Close-kin mark-recapture used to estimate bearded seal population abundance and demographics Presenter: Brian Taras , bdtaras-dfg@alaska.gov, Alaska Department of Fish and Game, retired Paul Conn , paul.conn@noaa.gov, Marine Mammal Lab, NOAA Alaska Fisheries Science Center Mark Bravington , mark.bravington@data61.csiro.au, CSIRO Marine Lab, Hobart, TAS, Australia Lori Quakenbush , lori.quakenbush@alaska.gov, Alaska Department of Fish and Game - Arctic Marine Mammal Program Andrzej Kilian , zej@diversityarrays.com, Diversity Arrays Technology Pty Ltd, University of Canberra, Bruce, ACT, Australia Aimée Lang , aimee.lang@noaa.gov, Southwest Fisheries Science Center, NOAA-Fisheries, La Jolla, CA Anna Bryan , anna.bryan@alaska.gov, Alaska Department of Fish and Game Bearded seals ( Erignathus barbatus ) use sea ice for pupping, nursing, and molting, and are a vital subsistence resource to coastal Alaska Natives. In 2012, bearded seals were listed as threatened under the U.S. Endangered Species Act, resulting in higher scrutiny for management assessments. To provide better estimates of abundance and vital rates, the Alaska Department of Fish and Game (ADF&G) and the National Marine Fisheries Service are using close-kin mark- recapture (CKMR) methods with genetic samples of bearded seals harvested by 13 Alaskan communities spanning the Bering, Chukchi, and Beaufort seas. This first application of CKMR in Alaska seeks to estimate the size of the bearded seal population needed for management. ADF&G’s ice seal biomonitoring program archived 1,759 samples with tooth ages, harvested from 1998 to 2020. A subset (282) was used to generate a ~3,000 single nucleotide polymorphism (SNP) panel; all samples were genotyped and sexed. After rigorous quality control, kin relationships were established for 1,484 seals (~1 million pairwise comparisons) at 2,569 loci. Kin relationships included two parent offspring pairs (POPs) and ~22 half sibling pairs (HSPs), four of which were potentially confounded with grandparent-grandoffspring pairs (GGPs). Mitochondrial DNA analysis identified 15 of the 22 HSPs (68%) as paternally related, providing substantial evidence of heterogeneity in adult male reproductive success consistent with observed territorial behavior of males during breeding. In addition, the lack of full sibling pairs suggests a lack of female to male fidelity. Underpinning the CKMR analysis is an age-structured population dynamics model composed of annual survival probabilities and fecundity parameters. The model incorporates probabilities associated with POPs, HSPs, and GGPs. The preliminary models assume that age is known, and abundance is constant over time. Models that did not accommodate heterogeneity in adult male breeding success resulted in a population abundance estimate of ~232,000 (CV = 0.21), however when included, the proportion of adult males breeding is estimated at 0.34 (SE = 0.15) leading to a 76% increase in abundance to ~409,000 (CV = 0.35). Our next steps are to refine the model (e.g., by including aging error) and to increase sampling to improve precision going forward.
Alaska Marine Science Symposium 2023 274
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