Abundance and distribution of Antarctic blue whales Balaenoptera musculus intermedia off the Queen Maud Land coast of Antarctica
The Antarctic blue whale Balaenoptera musculus intermedia was hunted to near extinction in the twentieth century. Current data on the abundance and distribution of the species are lacking owing to the difficulty and expense of surveys under adverse weather conditions in open-ocean habitats, and to the small population size. The most recently accepted global abundance estimate, based on the middle survey (1997/1998) of three circumpolar Antarctic surveys conducted between 1991/1992 and 2003/2004, was less than 1% of the original pre-whaling population size. The present study used a visual line-transect survey off the Queen Maud Land coast of Antarctica, in an area between 0° and 18° E and south of 67° S, in January 2014, to estimate the abundance of Antarctic blue whales in this area. Effort-accounted densities of sightings averaged 13.3 individuals per 1 000 nautical miles of survey effort (CV = 0.26) and reinforce recent findings that the area has significantly higher densities than averaged in circumpolar surveys (0.17–1.48 per 1 000 nautical miles). Distance sampling resulted in a population density estimate of 0.019 whales nautical-mile-2 (CV = 0.24) and an estimated abundance of 1 026 Antarctic blue whales (CV = 0.20, 95% CI 632–1 450) in the surveyed area. Obtaining such current estimates of abundance is crucial for assessment of the conservation status of the Antarctic blue whale population and for monitoring its recovery.
Keywords: baleen whale, distance sampling, endangered species, Southern Ocean, vessel survey, whale conservation