Effect of origin, sex and sea age of Atlantic salmon on their recapture rate after river ascent |
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| Authors: | E. Jokikokko I. Kallio-Nyberg E. Jutila I. Saloniemi |
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| Affiliation: | Finnish Game and Fisheries Research Institute, Bothnian Bay Fisheries Research Station, Simo;;Finnish Game and Fisheries Research Institute, Quark Fisheries Research Station, Vaasa;;Finnish Game and Fisheries Research Institute, Helsinki;;Department of Biology, Section of Ecology, University of Turku, Turku, Finland |
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| Abstract: | The recapture rate of Atlantic salmon (Salmo salar L.) after river ascent was examined by the trapping and tagging of ascending spawners in the lower reaches of the Simojoki River, which flows into the northern Baltic Sea. In 1997 and 1998, altogether 825 Carlin‐tagged salmon were released to continue their upstream migration. Of these, 800 could be sexed and categorized as reared (91%) or wild (9%) salmon. In 1997, most of the ascending salmon were multi‐sea‐winter (MSW) fish, whereas in 1998 almost all were one‐sea‐winter (1SW) male grilse due to the late trapping season. About 10% of all tagged fish were recaptured, two‐thirds of which were caught in the river before their descent to the sea. There was no difference in the recapture rate between salmon of wild (8.5%) or reared (9.5%) origin, or between females (11.6%) and males (9.3%). Generalized linear models for data from 1997 showed that the recapture rate increased with length and age of females, but that the opposite was true for males. River fishing did not seem to remove proportionally more early ascending salmon than fish that ascended later. |
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