Census of "Hawaiian" humpback whales (Megaptera novaeangliae) by individual identification

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Abstract
The numbers of humpback whales (Megaptera novaeangliae) that assembled in Hawaii in one winter and over the five winters from 1977 to 1981 were estimated by photographic identification of individual animals. Individual whales were identified by the black and white skin patterns on the underside of their flukes. Straight counts of identified individuals provide absolute minimum estimates, 521 in 1 year and 922 over 5 years. Calculations based on the number of repeat sightings of individuals were used to estimate total population size. These were based on the graph of the rate of discovery of "new," previously unidentified, whales and a form of the Bernoulli distribution, a theoretical distribution that estimates total numbers from multiple sightings of individuals in repeated sampling. The best estimates are 1000 in one winter and 2100 over five winters. The difference between one and five winters indicates that the population is not identical from year to year. Also, there are suggestions that the population increases in size over the winter period, and a small subpopulation may have a different behaviour pattern, possibly remaining in Hawaii longer, than the majority of animals.

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