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Stocking location and predation by marine fishes affect survival of hatchery‐reared Atlantic salmon smolts
Author(s) -
Thorstad E. B.,
Uglem I.,
Finstad B.,
Chittenden C. M.,
Nilsen R.,
Økland F.,
Bjørn P. A.
Publication year - 2012
Publication title -
fisheries management and ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 55
eISSN - 1365-2400
pISSN - 0969-997X
DOI - 10.1111/j.1365-2400.2012.00854.x
Subject(s) - salmo , gadus , fishery , predation , hatchery , biology , stocking , fish <actinopterygii> , ecology
Release strategies of hatchery‐reared Atlantic salmon, Salmo salar L., smolts were compared by studying survival and migration of smolts ( n = 99) and their predators (Atlantic cod, Gadus morhua L., n = 8; and saithe, Pollachius virens (L.), n = 2) during the first 37 km of the marine migration using acoustic telemetry. Survivorship was higher in smolts released at the river mouth (30%) compared with smolts released in the river (12%). This was likely due to mortality or reduced migratory behaviour in fresh water. The marine mortality was 37% during the first 2 km after leaving the river (at least 25% mortality because of predation from marine fishes), and total marine mortality over 37 km was 68%. Detection‐depth data were useful for evaluating whether the tagged smolts were alive or predated; mortality during the first 2 km of outward migration would have been underestimated at 26% instead of 37% without the analysis of depth detection. Transmitters from consumed post‐smolts remained in predators for up to 47 days (average 29 days).