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Ontogenetic allometry and body composition of harbour porpoises (Phocoena phocoena, L.) from the western North Atlantic

Published online by Cambridge University Press:  01 August 2002

W. A. McLellan
Affiliation:
Biological Sciences and Center for Marine Science, University of North Carolina at Wilmington, 601 South College Road, Wilmington, NC 28403, U.S.A.
H. N. Koopman
Affiliation:
Nicholas School of the Environment, Duke University Marine Laboratory, 135 Duke Marine Lab Road, Beaufort, NC 28516, U.S.A.
S. A. Rommel
Affiliation:
Florida Department of Environmental Protection, Marine Mammal Pathobiology Laboratory, 3700 54th Ave South, St Petersburg, FL 33711, U.S.A.
A. J. Read
Affiliation:
Nicholas School of the Environment, Duke University Marine Laboratory, 135 Duke Marine Lab Road, Beaufort, NC 28516, U.S.A.
C. W. Potter
Affiliation:
Division of Mammals, Smithsonian Institution, MRC Stop 108, Washington, DC 20560, U.S.A.
J. R. Nicolas
Affiliation:
National Marine Fisheries Service, Northeast Fisheries Science Center, 166 Water Street, Woods Hole, MA 02543, U.S.A.
A. J. Westgate
Affiliation:
Nicholas School of the Environment, Duke University Marine Laboratory, 135 Duke Marine Lab Road, Beaufort, NC 28516, U.S.A.
D. A. Pabst
Affiliation:
Biological Sciences and Center for Marine Science, University of North Carolina at Wilmington, 601 South College Road, Wilmington, NC 28403, U.S.A.
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Abstract

North Atlantic harbour porpoises Phocoena phocoena (L.) face considerable energetic challenges, as they are relatively small marine mammals with an intense reproductive schedule and a cold-water habitat. Post-natal growth of these porpoises was described using ontogenetic allometry and body composition techniques. The cross-sectional sample contained robust calves, immature, and mature porpoises (n = 122) incidentally killed in commercial fishing operations between 1992 and 1998. Total mass and the mass of 26 body components were measured using a standard dissection protocol. Most body components grew similarly in female and male porpoises. Blubber, brain and skull were negatively allometric, while muscle and reproductive tissues exhibited positive allometry. Female heart, liver, intestine and mesenteric lymph node grew at significantly higher rates than in males. Male locomotor muscle and pelvic bones grew significantly faster than in females. High growth rates for visceral and reproductive organs in porpoises, relative to other mammals, may underlie their early maturation and support their intensive, annual reproductive schedule. Relative to other cetaceans, porpoises seem to allocate a larger percentage of their total body mass to blubber. This allocation to blubber, which is greatest in calves (37% of body mass), may provide harbour porpoises with the thermal insulation required to live in cold water. The factors influencing growth rates and differential investments in body composition seem to change at various stages of a porpoise's life. Energy allocation in porpoises seems to shift from an emphasis on developing an insulative blubber layer in young animals to preparing the body for annual reproduction at sexual maturity.

Type
Research Article
Copyright
2002 The Zoological Society of London

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