Movements of humpback whales in Oceania, South Pacific

Résumé

To investigate movements of humpback whales among breeding and migratory areas of Oceania in the South Pacific Ocean, comparisons of individually identified whales were undertaken using catalogues from New Caledonia, Tonga, New Zealand, the Cook Islands and French Polynesia. These locations probably represent wintering grounds or migratory areas for the Group V and VI stocks, as recognised by the International Whaling Commission for management purposes. Comparisons were also made to small samples of photos from Colombia, Ecuador and the Antarctic Peninsula, representing wintering and feeding grounds of the Group I stock. Overall, the combined catalogues contained photographs of 912 individual whales, 767 of which were from Oceania. Twelve fluke matches were made, indicating movement between the following areas: New Caledonia and New Zealand (2); New Caledonia and Tonga (6, plus one made by dorsal fin); Tonga and the Cook Islands (2); the Cook Islands and French Polynesia (1, plus one made by dorsal fin); and between Ecuador and the Antarctic Peninsula (1). These results add to previously known connections between eastern Australia and the westerly component of Oceania (New Caledonia, Tonga and New Zealand). The data also suggest little movement between Oceania and Area I (western South America and the Antarctic Peninsula), although sample sizes for the latter region were too small to conclude this with certainty. The documented movement of some whales among portions of Oceania indicates that stock assessments based on combining regional estimates of abundance are likely to be positively biased, although this may be countered by problems of heterogeneity in sampling effort and whale distribution. In contrast with the recovery exhibited in Area IV and in the western portion of Area V, humpback whale abundance appears to remain low in Oceania, presumably because of overexploitation in the feeding grounds of Area VI and the easterly component of Area V.