Monthly indices of the post-smolt growth of Atlantic salmon from the Drammen River, Norway

Authors

  • J. L. McCarthy,

    Corresponding author
    1. * Department of Natural Resources Conservation, 160 Holdsworth Way, University of Massachusetts Amherst, Massachusetts 01003 U.S.A., National Marine Fisheries Service, 28 Tarzwell Drive, Narragansett, Rhode Island 02882 U.S.A. and § Norwegian Institute for Nature Research, Gaustadalleen 21, NO-0349 Oslo, Norway
      †Tel.: +1 413 695 9600; fax: +1 413 545 4358; email: oceanjennifer@yahoo.com
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  • K. D. Friedland,

    1. * Department of Natural Resources Conservation, 160 Holdsworth Way, University of Massachusetts Amherst, Massachusetts 01003 U.S.A., National Marine Fisheries Service, 28 Tarzwell Drive, Narragansett, Rhode Island 02882 U.S.A. and § Norwegian Institute for Nature Research, Gaustadalleen 21, NO-0349 Oslo, Norway
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  • L. P. Hansen

    1. * Department of Natural Resources Conservation, 160 Holdsworth Way, University of Massachusetts Amherst, Massachusetts 01003 U.S.A., National Marine Fisheries Service, 28 Tarzwell Drive, Narragansett, Rhode Island 02882 U.S.A. and § Norwegian Institute for Nature Research, Gaustadalleen 21, NO-0349 Oslo, Norway
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†Tel.: +1 413 695 9600; fax: +1 413 545 4358; email: oceanjennifer@yahoo.com

Abstract

Indices of the monthly post-smolt growth of three maturity groups of Atlantic salmon Salmo salar from the Drammen River in Norway were examined. Scale samples were collected from 1983 to 2003, providing a retrospective growth history for 2854 individuals. Overall post-smolt growth of all three maturity groups decreased throughout the study period. When the post-smolt year was segmented into 8 monthly indices, there was a significant decline in growth during the fourth and fifth month, typically months of maximum growth. The pre-fishery abundance of one and two sea-winter fish from Norway also showed a decline throughout the study period and was positively correlated to the post-smolt growth of fish returning to the Drammen River. Freshwater growth was negatively correlated to the pre-fishery abundance, thus indicating that factors affecting post-smolt growth during the fourth and fifth months at sea may be responsible for declining return numbers in Norway.

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