Research Document - 2015/008

Abundance estimates of the Eastern Canada-West Greenland bowhead whale (Balaena mysticetus) population based on genetic capture-mark-recapture analyses

By Timothy R. Frasier, Stephen D. Petersen, Lianne Postma, Lucy Johnson, Mads Peter Heide Jørgensen, and Steven H. Ferguson

Abstract

We conducted Bayesian analyses of genetic capture-mark-recapture data to estimate abundance of the Eastern Canada-West Greenland (EC-WG) bowhead whale population. We employed two different analytical approaches, one that ignored location data and treated the entire data set as one large capture-mark-recapture data set, and another that used location-specific data to explicitly account for the presence of unsampled areas. For both approaches we conducted analyses based on two different data sets, one containing data from throughout the entire study period (19 years), and the other containing a 5-year subset of the data. The rationale was that the population size may have changed throughout the 19 years of sample collection, which would bias subsequent estimates. A total of 1,177 samples, from 9 locations throughout the distribution, were genotyped at 21 microsatellite loci. Of these, 992 unique genotypes were identified, with 49 recaptures occurring between years and/or locations. Both estimates for the 5-year data set were smaller than for the 19-year data set, which is consistent with a population increase throughout the study period. Although the estimates differ for each approach, our best estimate of total population abundance is 7,660 individuals (95% HDI 4,500-11,100). We also obtained location-specific estimate for four areas: Greenland (2,854, 95% HDI 1,230-6,460); Igloolik (2,760, 95% HDI 1,980-5,050); Pangnirtung (3,500, 95% HDI 1,700-4,960); and Repulse Bay (38, 95% HDI 20-124).

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