Beluga Whale (Delphinapterus leucas)
The beluga whale, Delphinapterus leucas, is an arctic adapted odontocete. They are typically 3-5m in length and weigh between 500 and 1500kg. Calves are relatively dark in colour, changing from brown to bluish and gray before becoming a striking pure white at sexual maturity.
Our work deals primarily with the endangered St. Lawrence Estuary beluga population. This is the southernmost population of this primarily arctic species and is believed to be geographically isolated from other populations. In the summer, the distribution of St. Lawrence beluga is centered around the Saguenay, but in the winter they are found from Tadoussac (at the mouth of the Saguenay) to the Gulf of St. Lawrence. The St. Lawrence beluga is possibly best known for its high contamination load. Toxicological studies and necropsies of dead beached whales have revealed high levels of mercury, lead, PCB’s, DDT, Mirex, and benzo[a]pyrene metabolites, as well as large numbers of tumors, non-neoplastic lesions, and neoplasms.
Prior to 1885, it is estimated there were at least 5000 St. Lawrence beluga whales. However, from the 1500’s to the 1950’s they were heavily hunted. In the 1920’s the Canadian government even placed a bounty on the St. Lawrence beluga because they were blamed for declining fish stocks and 2,233 bounties were paid. The St. Lawrence beluga has been officially protected by the Canadian Fisheries Act since 1979, but has failed to show significant population recovery. This lack of recovery is believed to be due to extrinsic factors such as harassment, habitat degradation, and contamination by toxic chemicals as well as intrinsic factors such as the genetic status of the population.
We have been working in collaboration with the Group de Recherche et d’Éducation sur les Mammifères Marins (GREMM) since 1994,
collecting skin biopsies from known individuals for genetic analyses. Individual-specific DNA profiles are being developed using a combination of molecular gender determination and genotypes from the mitochondrial control region, microsatellite loci, and Major Histocompatibility Complex loci. The genetic data, in conjunction with the GREMM’s photo-identification and long-term association research program, is being used to assess levels of genetic variability, genetic consequences of reduced population size, and population structure in this endangered population. This will allow an evaluation of factors contributing to the lack of recovery of this population and will ultimately be applied to population conservation and management strategies.
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Fig. 1:Molecular gender determination. Males have two bands, females have one band
Fig. 2 Skin sample collected with crossbow and biopsy dart (H. Hughes, www.gremm.org).
Murray,BW, Michaud,R and White, BN (1999) Allelic and haplotype variation
of Major Histocompatibility Complex class II DRB1 and DQB loci in the St Lawrence beluga (Delphinapterus leucas). Molecular Ecology 8, 1127-1159.
Murray, BW and White, BN (1998) Sequence variation at the major histocompatibility complex DRB loci in beluga (Delphinapterus leucas) and the narwhal (Monodon monoceros). Immunogenetics, 48: 242-252.
Brennin R, Murray B, Friesen M Postma L, Maiers D, Clayton J, White BN (1997).Population genetic structure of beluga whales (Delphinapterus leucas): mitochondrial sequence variation within and among North American populations. Can J. Zool. 75, 795-802.
Murray, BW, Malik,S and White, BN (1995) Sequence variation at the major histocompatibility Complex Locus DQB in Beluga Whales (Delphinapterus leucas).Mol. Biol. Evol. 12, 582-593.
Patenaude N and BN White.(1995) Skin biopsy sampling of beluga carcasses: Assessment of biopsy darting factors for minimal wounding and effective retrieval on beluga whales. Marine Mammal Science 11(2): 163-171.
Patenaude N, J Quinn, P Beland, M Kingsley and BN White (1994) Genetic variation of the St. Lawrence beluga whale population assessed by DNA fingerprinting. Molecular Ecology 3: 375-381.
Patenaude, NJ, EA Guglich, and BN White (1993) Assessment of genetic variation in two beluga whale (Delphinapterus leucas) populations from DNA fingerprints: preliminary results. Muskox 39: 196-202.
Shaw, C., Wilson, P., and White B.N. (2003) A reliable molecular method of gender determination for a range of mammals. J. Mammalogy 84(1), 123-128.