Population size of humpback whale, Megaptera novaeangliae, in waters off the Pacific coast of Mexico

The humpback whale (Megaptera novaeangliae) is a cosmopolitan species whose stocks were drastically decreased by commercial whaling practices prior to 1967. The North Pacific population was estimated to be between 15,000 and 20,000 animals before the practice of whaling. At the time of the commencem ent of its international protection in 1967, this population may have been reduced to fewer than 1000 individuals. The Pacific coast of Mexico and the Revillagigedo Archipelago constitute one of the main breeding and calving areas for North Pacific humpback whales. The objective of this paper is to present an estimation of abundance of humpback whales in this region based on photographic identification of individual animals. Estimates of populati on size were obtained by using mark and recapture models for both closed an d open populations, with each year representing a capture occasion. A total of 1184 humpback whales were identified in Mexican waters between 1986 and 1993. The best estimates of population size for the Mexican stocks were th ose provided by the modified Jolly-Seber method: 1813 (95% CI: 918-2505) fo r the coastal st 914 (95% CI: 590-1193) for the Revillagigedo stock in 1991 .