AGE-LENGTH RELATIONSHIPS IN HUMPBACK WHALES: A COMPARISON OF STRANDINGS IN THE WESTERN NORTH ATLANTIC WITH COMMERCIAL CATCHES

Authors

  • Peter T. Stevick

    1. College of the Atlantic, 105 Eden Street, Bar Harbor, Maine 04609, U. S. A.
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    • 1

      Current address: Sea Mammal Research Unit, Gatty Marine Laboratory, University of St. Andrews, St. Andrews, Fife KY16 8LB, Scotland; e-mail: pts2@st-andrews.ac.uk.


Abstract

Strandings of previously identified individuals, while rare, provide an opportunity to examine age-length relationships in humpback whales (Megaptera novacangliae) from the North Atlantic. Ages and lengths of 23 individuals are presented: 11 females and 12 males, 9 of known age and 14 with estimated minimum ages. Lengths ranged from 853 to 1, 430 cm, ages 0.5–17 yr. These individuals were generally smaller and more variable in size at age than reported from commercial catches. Fifteen of the stranded individuals were four years of age or younger, while few of the animals taken by whalers were this young, and these probably represented the larger individuals in these age categories. Thus the data presented herein help to give more definition to the early growth curve for the humpback whale than has previously been available. Growth equations illustrate a difference of about one meter in asymptotic length through age five between stranding and catch data. The close fit of growth models to data from younger and older animals separately and the difficulty of fitting a single growth model to animals of all ages, could indicate that a dynamic or staged growth pattern exists in this species.

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