The 2005 Galápagos humpback whale expedition: a first attempt to assess and characterise the population in the Archipelago

It has been known for some time that humpback whales (Megaptera novaeangliae) occur in waters of the Galapagos Islands, an oceanic archipelagolocated 1,000km west of Ecuador, South America (1°S, 91°W), but their presence there has been poorly documented. Although presumed, nolinkage has been established between Galapagos and southeast Pacific humpback whales (Breeding Stock G), the nearest breeding stock. Anexpedition to Galapagos was carried out between 31 August and 10 September 2005 to document the presence of humpback whales, their distribution,and their relationship to other stocks in the Pacific. Surveys covered 722km of the central and southern parts of the archipelago. Only one adultwith a newborn calf was found at Santa Fe Island (0°47’S, 90°05.1’W), yielding an encounter rate of 0.27 whales per 100km of survey. A hydrophonewith a response frequency range of 0.25–25kHz was dropped 25 times, but no whale sounds were heard. A skin sample was obtained by darting ofthe adult at Santa Fe, and was used for genetic analysis of the mtDNA control region. The haplotype of the Galapagos specimen has been found ina few individuals sampled previously off Colombia, Ecuador and the Antarctic Peninsula, thus establishing at least some degree of relatedness withBreeding Stock G. The observations, combined with a compilation of historical and recent sighting information in the archipelago, support the ideathat Galapagos is a breeding area for the species. Further studies are needed to establish the level of discreteness, size and other basic aspects of theGalapagos humpback whale population.