MEPS 258:263-273 (2003) - doi:10.3354/meps258263
North Atlantic humpback whale abundance and rate of increase four decades after protection from whaling
Peter T. Stevick1,11,*, Judith Allen2, Phillip J. Clapham3, Nancy Friday4, Steven K. Katona2, Finn Larsen5,12, Jon Lien6, David K. Mattila7, Per J. Palsbøll8,13, Jóhann Sigurjónsson9, Tim D. Smith3, Nils Øien10, Philip S. Hammond1
ABSTRACT: Humpback whales Megaptera novaeangliae in the North Atlantic Ocean were severely depleted by exploitation. With legal protection since 1955, substantial recovery is likely to have occurred, but information on abundance and rates of increase has been limited. We present an assessment of humpback whale abundance in the North Atlantic Ocean based upon capture- recapture estimates using naturally marked individuals. These data result from a long-term collaborative effort combining large-scale dedicated projects and incidental data collection, leading to extensive geographical coverage. The application of robust statistical techniques produces estimates of greater accuracy and precision than has previously been possible. Abundance estimates ranging from 5930 to 12580 individuals, with coefficients of variation (CVs) from 0.07 to 0.39, were calculated for the West Indies breeding population using data from 1979 to 1993. The most precise estimate for the West Indies breeding population is 10752 (CV = 0.068) for 1992 and 1993. Due to application of new analytical methods, these estimates are larger and more precise than those previously published from similar time periods. The average rate of increase for the West Indies breeding population over a 14 yr period was estimated to be 0.031 (SE = 0.005). The best available estimate for the entire North Atlantic population of humpback whales is 11570 (95% CI 10290 to 13390) based upon samples from 1992 and 1993. However, this estimate may be biased downwards to an unknown extent due to heterogeneity in capture probabilities that do not influence the West Indies estimates.
KEY WORDS: Abundance estimation · Population increase · Humpback whale · Capture-recapture
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