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Identification of stock components using morphological markers

Authors

  • B. J. McAdam,

    Corresponding author
    1. Institute of Biology, University of Iceland, Sturlugata 7, Reykjavik 101, Iceland
      Tel.: +44 131 258 4801; email: bruce@marice.is
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  • T. B. Grabowski,

    1. Institute of Biology, University of Iceland, Sturlugata 7, Reykjavik 101, Iceland
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    • Present address: U.S. Geological Survey, Texas Cooperative Fish & Wildlife Research Unit, Texas Tech University, Agricultural Sciences 218 MS 2120, Lubbock, TX 79409-2120, U.S.A.

  • G. Marteinsdóttir

    1. Institute of Biology, University of Iceland, Sturlugata 7, Reykjavik 101, Iceland
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Tel.: +44 131 258 4801; email: bruce@marice.is

Abstract

This study investigated the development of a quantitative method for distinguishing stock components of Icelandic cod Gadus morhua based on visual examination of morphology. The stock is known to be structured into genetically distinct geographic components (north and south of Iceland) and behavioural types that spawn sympatrically. Differences in morphology were tested between locations, genotypes (a proxy for behaviour) and sexes. Results show morphological markers on the head, fins and body of G. morhua that are correlated with the sex, genotype of the fish at the pantophysin (pan-I) locus and the location at which the fish were caught. Females were found to have relatively deep bodies, and the pan-IBB genotype (associated with deep-water feeding behaviour) have greater gaps between their fins. Overall, morphology is more useful for distinguishing sympatric genotypes but less powerful at identifying genetically distinct geographic sub-populations, perhaps because counter-gradient evolution reduces phenotypic differences even with an underlying genetic cause.

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