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Do triploid S almo trutta stocked into a chalk stream in the spring prey on wild S almo salar smolts?
Author(s) -
Riley W. D.,
Davison P. I.,
Ives M. J.,
Maxwell D. L.
Publication year - 2013
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/fme.12023
Subject(s) - salmo , brown trout , stocking , predation , biology , fishery , spring (device) , zoology , ecology , fish <actinopterygii> , physics , thermodynamics
The predation impact of recently stocked triploid brown trout, S almo trutta L., on migrating wild A tlantic salmon, S almo salar L., smolts was investigated in two field‐based experiments. The first experiment employed a unique experimental facility to monitor 57 wild S . salar smolts through an enclosure containing a known density of stocked S . trutta to determine a predation rate. None of these smolts were preyed upon by the stocked S . trutta . The second experiment investigated the diet of free‐ranging stocked triploid S . trutta in a chalk stream during the spring. Although at least 6% of the free‐ranging stocked triploid S . trutta became piscivorous on P hoxinus phoxinus (L.), the results suggest that large, recently stocked, triploid S . trutta with a high condition factor do not represent a predation threat to wild S . salar smolts. However, it is recommended that a precautionary approach is maintained and the findings are not generalised until further investigation permits explicit management advice to be developed, and that the stocking of large triploid S . trutta is avoided before May/ June (regional variations to apply) each calendar year, where this can reasonably be achieved.