Abundance and mtDNA differentiation of humpback whales (Megaptera novaeangliae) in the Shumagin Islands, Alaska

摘要

Despite extensive research on humpback whales (Megaptera novaeangliae (Borowski, 1781)) in parts of the North Pacific, little research has focused on the whales feeding in coastal waters west of Kodiak Island in the Gulf of Alaska. To extend research westward in the North Pacific, small-boat surveys were conducted near the Shumagin Islands during the summers of 1999-2002. Photographs of the natural markings of humpback whales were collected, representing 413 sightings of 171 individual whales. Small samples of skin tissue were collected from 20 individuals, including two mother-calf pairs, for sex identification and comparison of mtDNA haplogroups with previously published results from surveys in other regions of the North Pacific. Individual identification photographs were used in mark-recapture analysis to estimate abundance for the Shumagin Island region. The best estimate was given by a modified Jolly-Seber method: N = 410 (95% Cl: 241-683) for 2002. Comparison of photographs with archived photographs from throughout the North Pacific revealed four migratory destinations for 13 of the Shumagin Islands whales: Hawai'i, Japan, offshore Mexico, and coastal Mexico. The frequencies of mtDNA haplogroups differed significantly from those in three other sampled feeding grounds: California, southeastern Alaska, and Prince William Sound. The haplogroup frequencies and migratory destinations of individuals suggested an affinity with the Hawaiian wintering ground but data are insufficient to associate whales off the Shumagin Islands with any surveyed breeding ground.