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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

1Sea Mammal Research Unit, Gatty Marine Laboratory, University of St Andrews, Fife KY16 8LB, Scotland
2College of the Atlantic, 105 Eden Street, Bar Harbor, Maine 04609, USA
3Northeast Fisheries Science Center, 166 Water Street, Woods Hole, Massachusetts 02543-1026, USA
4Cetacean Assessment and Ecology Program, National Marine Mammal Laboratory, AFSC/NMFS, Seattle, Washington 98115-6349, USA
5Greenland Institute for Natural Resources, PO Box 570, 3900 Nuuk, Greenland
6Biopsychology Programme and Ocean Sciences Centre, Memorial University of Newfoundland, St. Johns A1C 5S7, Canada
7Center for Coastal Studies, PO Box 1036, Provincetown, Massachusetts 02657, USA
8Department of Population Biology, University of Copenhagen, 2100 Copenhagen Ø, Denmark
9Marine Research Institute, Skulagata 4, PO Box 1390, 121 Reykjavik, Iceland
10Institute of Marine Research, PO Box 1870, Nordnes, 5817 Bergen, Norway
11Present address: PO Box 93, Rockport, Maine 04856-0093, USA
12Present address: Danish Institute for Fisheries Research, Charlottenlund Castle, 2920 Charlottenlund, Denmark
13Present address: University of California at Berkeley, Ecosystem Sciences Division - ESPM, California 94720-3110, USA

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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