Site-fidelity and movement ranges of southern right whales in Antarctic Area IV inferred from genetic tagging
Luis A. Pastene, Takashi Hakamada, Paola Acuna, Mioko Taguchi, Mutsuo Goto, Koji Matsuoka and Shigetoshi Nishiwaki
International Whaling Commission
Genetic markers (‘tags’) were employed to identify individual southern right whales in order to assess their site-fidelity and sex-specific ranges in the Antarctic Area IV (i.e., between 80°-135°E and south of 60°S). In total, 157 biopsy samples were collected as skin biopsies from free-ranging whales during fourteen summer surveys. The DNA was extracted from each biopsy sample and genotyped at fourteen microsatellite loci, sequenced for 430 nucleotides of the mtDNA control region, and the sex determined by the presence of a Y-chromosome specific locus. The overall probability of identity (the probability that two unrelated individuals from the same panmictic population have identical multi-locus genotypes) was estimated at 1.95 x10-10. After removal of biopsies with identical multi-locus genotypes sampled during the same sighting, the number of individuals was reduced to a total of 153. Eight ‘mark-recapture’ incidences were detected (four males and four females). Individual matching by multi-locus genotypes was supported by mtDNA, sex determination, and in two cases where pictures were available, by photo-identification. These eight re-captures suggested that individual whales tended to return to the same location in the Antarctic in subsequent years. The average longitudinal dispersal ranges were 13°06’ and 7°15’ in males and females, respectively. The time span between the ‘mark’ and the ‘recapture’ ranged from 3-13 years with an average at 7.3 years. Preliminary application of a ‘mark-recapture’ method based on an open population model, resulted in abundance estimates in Area IV similar to those obtained using sighting survey data and the Line Transect Method in the same area and similar period.