Demographic distinctness of the Pacific Coast Feeding Group of gray whales (Eschrictius robustus)

January 19, 2011

Principal Investigator: Aimee Lang, Marine Mammal Genetics Program

Gray whaleWithin the North Pacific, gray whales are recognized as distinct eastern and western populations. Although both populations were severely reduced by whaling, the eastern population is generally considered to have recovered while the western population has remained highly depleted. Genetic differentiation of the small western population from the much larger population of gray whales found in the eastern North Pacific was initially described on the basis of mitochondrial DNA (mtDNA) haplotype frequencies (LeDuc et al. 2002). Subsequent studies utilizing microsatellites provided additional support for recognition of the two populations as distinct units, with small but statistically significant differences in microsatellite allele frequencies identified between the two populations (Lang et al. 2010)

Structure within the eastern population of gray whales may also exist. Evidence from photo-identification research (Darling 1984, Calambokidis et al. 2002, 2010) as well as a recent genetic study (paper presented by Tim Frasier at the annual meeting of the International Whaling Commission Scientific Committee in 2010) suggests that the group of gray whales (referred to as the Pacific Coast Feeding Group, PCFG) feeding in more southern waters between northern California and southeastern Alaska may represent a demographically distinct stock. To further investigate this hypothesis, this project will use data from mtDNA control region sequencing and microsatellite genotyping to evaluate the level of differentiation between PCFG of gray whales and gray whales feeding in more northern areas.


Calambokidis, J., J.D. Darling, V. Deecke, P. Gearin, M. Gosho, W. Megill, C.M. Tombach, D. Goley, C. Toropova and B. Gisborne. 2002. Abundance, range and movements of a feeding aggregation of gray whales (Eschrichtius robustus) from California to southeastern Alaska in 1998. Journal of Cetacean Research and Management 4:267-276.

Calambokidis, J., J.L. Laake and A. Klimek. 2010. Abundance and population structure of seasonal gray whales in the Pacific Northwest, 1998 - 2008. Paper IWC/62/BRG32 submitted to the International Whaling Commission Scientific Committee. 50 pp.

Darling, J.D. 1984. Gray whales (Eschrichtius robustus) off Vancouver Island, British Columbia. in M.L. Jones, S.L. Swartz and S. Leatherwood, eds. The Gray Whale, Eschrichtius robustus. Academic Press, New York.

Lang, A.R., D. W.Weller, R. G. LeDuc, A.M. Burdin, and R. L. Brownell, Jr. 2010. Genetic differentiation between the western and eastern gray whale (Eschrichtius robustus) populations using microsatellite markers. Paper SC/62/BRG11 presented to the International Whaling Commission Scientific Committee. 18 pp.

LeDuc, R.G., D.W. Weller, J. Hyde, A.M. Burdin, P.E. Rosel, R.L. Brownell, Jr., B. Wursig and A.E. Dizon. 2002. Genetic differences between western and eastern gray whales (Eschrichtius robustus). Journal of Cetacean Research and Management 4:1-5.