Research Document - 2001/050
Stock discrimination of belugas (Delphinapterus leucas) hunted in eastern Hudson Bay, northen Québec, Hudson Strait, and Sanikiluaq (Belcher Islands), using mitochondrial DNA and 15 nuclear microsatellite loci
By B.G.E. de March and L.D. Maiers
Abstract
We examined the possibility that eastern Hudson Bay (EHB) beluga were hunted by the communities outside of the EHB arc. The molecular genetics of 100 belugas hunted from Sanikiluaq on the Belcher Islands, 126 from EHB communities, 137 from north-western Québec and Hudson Strait communities (65/137 from 1983-1997 with complete genetic data, 115/137 from 1998-1999 only mtDNA ), and 378 from other geographic areas which might share stocks or are known to be genetically similar were examined. Individuals and sample populations were characterized with a mitochondrial DNA (mtDNA) d-loop sequence of 324 base pairs which described 32 different haplotypes (maternally inherited) and with 15 nuclear microsatellite loci (inherited from both parents).
Stocks could most often be defined from different mixtures of haplotypes in different sample populations. There was weak genetic differentiation among populations on the basis of microsatellites, however, there was considerable overlap of microsatellite alleles frequencies among all populations. All genetic results supported the hypotheses that belugas hunted in EHB and Sanikiluaq are from different stocks. However some individuals from each area had genotypes that strongly associated them with the other stock. Large genetic diversities in samples from Northern Québec and northern Hudson Bay samples may mean that mixtures of stocks were hunted in these areas. On the basis of microsatellite results, it is possible that most examined populations interbreed.
Belugas from both the Nastapoka River (1984-1995) and other locations on the EHB arc (1993-1997) were genetically similar, and were characterized by high frequencies of two haplotypes which are not common elsewhere. Belugas from the Nastapoka River also had low haplotype and microsatellite allelic diversities. Belugas sampled from other locations in the EHB arc in the 1990s had these same haplotypes, but also a low frequency of western haplotypes. These later samples also had a slightly higher microsatellite diversity. 17% of belugas hunted in EHB (all 1984-1997) had genotypes that resemble western Hudson Bay populations. However such belugas were not sampled every year.
The genetic composition of belugas hunted in Sanikiluaq over five years was consistent. These belugas had both a high haplotype and microsatellite diversity, however proportions differed from other western Hudson Bay populations. These belugas may be a different stock or a consistent mixture of other stocks. Beluga males from Sanikiluaq may have a slightly higher genetic diversity than females. Approximately 10% of belugas hunted from Sanikiluaq have genotypes that resemble EHB (1984-1997) more than they resemble other populations.
Since genetic characteristics overlapped among the populations we examined, it was impossible to distinguish with belugas that were outside of their summering range and those that had genetic characteristics more typical of other population. Nevertheless, 31% of belugas from northwestern Québec and Hudson Strait had genotypes that were more probable in EHB, again this value not consistent between communities and years. EHB genotypes comprised 20% in northern Hudson Bay, and 7% in Kimmirut.
Belugas from the Churchill, Nastapoka, and St. Lawrence Rivers have low genetic diversities. This may be a characteristic of populations that frequent estuaries and/or may be due to overhunting in the past.
Some genetic patterns described can be explained by post-glacial dispersion.
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