North Atlantic humpback whale abundance and rate of increase four decades after protection from whaling

Abstract

Humpback whales Megaptera novaeangliae in the North Atlantic Ocean were severely\ndepleted by exploitation. With legal protection since 1955, substantial recovery is likely to have\noccurred, but information on abundance and rates of increase has been limited. We present an\nassessment of humpback whale abundance in the North Atlantic Ocean based upon capturerecapture\nestimates using naturally marked individuals. These data result from a long-term collaborative\neffort combining large-scale dedicated projects and incidental data collection, leading to\nextensive geographical coverage. The application of robust statistical techniques produces estimates\nof greater accuracy and precision than has previously been possible. Abundance estimates ranging\nfrom 5930 to 12 580 individuals, with coefficients of variation (CVs) from 0.07 to 0.39, were calculated\nfor the West Indies breeding population using data from 1979 to 1993. The most precise estimate for\nthe West Indies breeding population is 10 752 (CV = 0.068) for 1992 and 1993. Due to application of\nnew analytical methods, these estimates are larger and more precise than those previously published\nfrom similar time periods. The average rate of increase for the West Indies breeding population over\na 14 yr period was estimated to be 0.031 (SE = 0.005). The best available estimate for the entire North\nAtlantic population of humpback whales is 11 570 (95% CI 10 290 to 13 390) based upon samples from\n1992 and 1993. However, this estimate may be biased downwards to an unknown extent due to\nheterogeneity in capture probabilities that do not influence the West Indies estimates.