Journal Article

Seasonal marine feeding and body condition of sea trout (<i>Salmo trutta</i>) at its northern distribution

A.H. Rikardsen, P-A. Amundsen, R. Knudsen and S. Sandring

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 63, issue 3, pages 466-475
Published in print January 2006 | ISSN: 1054-3139
Published online January 2006 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2005.07.013
Seasonal marine feeding and body condition of sea trout (Salmo trutta) at its northern distribution

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The seasonal marine feeding pattern of sea trout was studied from March to December 2001 in two large fjords situated at latitudes 69°N and 66°N in the northern part of Norway. Despite low sea temperatures and high salinity, sea running trout were caught during all sampling occasions in both fjords. The trout had fed extensively on marine crustaceans (shrimps, amphipods, and krill) and polychaetes during early and late winter, and had a stable or increasing condition factor during this period. In summer and autumn, the trout fed predominantly on fish, mainly juvenile herring. Food consumption rates were lowest during late autumn and early winter (October–December) in both fjords, while trout in the southernmost fjord had the highest consumption rates from April to August and trout in the northernmost fjord from May to September. These patterns in both fjords matched the seasonal variations in condition factor and relative lipid content of the fish during the same periods. The marine winter migration of these northern sea trout populations appears to be a feeding migration in which the fish maintain or increase their body condition, representing a previously undocumented alternative to the more common life history strategy of over-wintering and starvation in freshwater at the northern distribution of this species.

Keywords: anadromy; brown trout; diet; fat; food consumption; growth; life history; lipid; migration; season; winter

Journal Article.  5670 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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