Population Genetics of St. Lawrence Beluga Whales, Assessment of Inbreeding by DNA Fingerprinting and Assessment of Biopsy Darting Factors for Minimal Wounding and Effective Sample Retrieval

Abstract

The endangered St. Lawrence beluga (Delphinapterus leucas) population is not recovering from severe depletion despite its protected status over the past 20 years. DNA fingerprinting analysis of St. Lawrence beluga whales with three minisatellite probes (Jeffreys 33.6, 33.15 and Ml3) indicate a reduced level of genetic variability compared to Mackenzie Delta animals. The average band-sharing between individuals of the St. Lawrence beluga population for the three probes (0.534, 0.573, 0.478) was significantly higher than the average band-sharing of the Mackenzie Delta beluga population for the same probes (0.343, 0.424, 0.314). Higher levels of mean homozygosity in the isolated St. Lawrence belugas (0.33 vs 0.21) as well as a high degree of relatedness suggest that this population is inbred and that inbreeding depression is a factor in the lack of recovery of the St. Lawrence beluga population. Because sampling of some beluga populations may be biased, there is the need of alternative sampling procedures such as biopsy darting. To evaluate the impact of biopsy darting on beluga whales, different combinations of dart and stop sizes were tested on fresh beluga carcasses and the effect of different factors on the success of retrieval and the extent of wounding were evaluated. Tips with smaller diameters were more likely to retrieve a sample than those with larger diameters (p <0.05) and longer tips were also more likely to retrieve a sample than shorter tips (p < 0.10). The force of impact, a function of draw weight and distance, had a significant effect on the severity of wounding (p<0.05). The samples obtained from all biopsy darts tested yielded sufficient amounts of DNA for genetic analysis.