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Morphological variation between lake- and stream-dwelling rock bass and pumpkinseed populations

Authors

  • J. Brinsmead,

    1. Ontario Ministry of Natural Resources, Sudbury, Ontario, P3G 1E7, Canada
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  • M. G. Fox

    Corresponding author
    1. Environmental & Resource Studies Program and Department of Biology, Trent University, Peterborough, Ontario, K9J 7B8, Canada
      ‡Author to whom correspondence should be addressed. Tel: +1 705 748 1011; fax +1 705 748 1569; email: mfox@trentu.ca
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‡Author to whom correspondence should be addressed. Tel: +1 705 748 1011; fax +1 705 748 1569; email: mfox@trentu.ca

Abstract

Pumpkinseed Lepomis gibbosus and rock bass Ambloplites rupestris stream populations of both sexes were significantly different in external morphology from lake populations in a central Ontario, Canada, watershed. The predictions that stream fishes would be more slender-bodied, and have a more anterior placement of lateral fins than lake fishes were generally supported. The prediction that stream fishes would have a more robust caudal peduncle was partially supported. The prediction that fin size would be larger in stream fishes was not supported, as lake rock bass generally had longer and wider fins than those from stream sites. The results suggest that in some species, smaller fins may be favoured in stream-dwelling individuals because the reduction of drag during swimming more than compensates for their reduced power and propulsion efficiency in a current. Smaller fin size in stream-dwelling centrarchids may be related to their body shape, or to their low usage of fast-moving water within the streams they inhabit.

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