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Migratory timing, marine survival and growth of anadromous brown trout Salmo trutta in the River Imsa, Norway
2009 (English)In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 74, no 3, 621-638 p.Article in journal (Refereed) Published
Abstract [en]

The aim of the paper was to study sea migration, growth and survival of brown trout Salmotrutta of the River Imsa, 1976–2005. The migratory S. trutta were individually tagged and fishleaving or entering the river were monitored daily in traps located near the river mouth. Themean annual duration of the sea sojourn was 6–9 months for first-time migrants moving to seabetween January and June. It was 8–18 months for those migrating to sea between July andDecember. Veteran migrants stayed 12 months or less at sea and most returned to the river inAugust. Early ascending fish stayed the longest in fresh water because most returned to sea inApril to May. The day number of 50% cumulative smolt descent correlated negatively withmean water temperature in February to March and the February North Atlantic Oscillationindex (NAOI). Mean annual sea growth during the first 2 years after smolting was higher for S.trutta spending the winter at sea than those wintering in the River Imsa. First year's sea growthwas lower for S. trutta descending in spring than autumn. For first-time migrants, it correlatednegatively with the February NAOI of the smolt year. Sea survival was higher for spring thanautumn descending first-time migratory S. trutta with a maximum in May (149%). Number ofanadromous S. trutta returning to the river increased linearly with the size of the cohort movingto sea, with no evidence of density-dependent sea mortality. Sea survival of S. trutta smoltsmoving to sea between January and June correlated positively both with the annual number ofAtlantic Salmo salar smolts, the specific growth rate at sea, and time of seaward migration inspring. This is the first study indicating how environmental factors at the time of seawardmigration influence the sea survival of S. trutta.

Place, publisher, year, edition, pages
2009. Vol. 74, no 3, 621-638 p.
Keyword [en]
mortality, NAOI, Salmo salar, Salmo trutta, temperature, time series
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:kau:diva-34224DOI: 10.1111/j.1095-8649.2008.02152.xISI: 000263040100010OAI: oai:DiVA.org:kau-34224DiVA: diva2:754014
Available from: 2014-10-09 Created: 2014-10-09 Last updated: 2014-10-15Bibliographically approved

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Jonsson, Bror
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