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Potential for sea ranching rainbow trout, Oncorhynchus mykiss (Walbaum): evidence from trials in two Norwegian fjords
Author(s) -
JONSSON N.,
JONSSON B.,
HANSEN L. P.,
AASS P.
Publication year - 1993
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/j.1365-2109.1993.tb00641.x
Subject(s) - rainbow trout , fishery , fjord , biology , hatchery , stocking , commercial fish feed , zoology , electrofishing , fish <actinopterygii> , aquaculture , oceanography , geology
. In total, 10014 hatchery‐reared 1+ and 2+ rainbow trout, Oncorhynchus mykiss (Walbaum), were released near the mouth of the River Imsa, south‐western Norway, and in the Oslofjord, south‐eastern Norway. The reported recapture rate was significantly higher in the Oslofjord(15·4%) than at Ims(3·6%). Between 70 and 80% of the recaptures were made in the year of release. The fish were recaptured in rivers and the sea along the Norwegian coast, most of them near the release sites. In total, 60% were recaptured in salt water and 40% in fresh water. Fish released in the Oslofjord were largely captured with rod and line. Of those released at Ims most of the freshwater recaptures were made in a fish trap in the River Imsa. In salt water most fish were captured by nets. Specific growth rate varied inversely with body weight at release, decreased with time after release and decreased faster for fish released in the Oslofjord than at Ims. In general, the proportion of fish recaptured increased with mean fish weight at release. Recaptured biomass per 1000 fish released was higher when released in the Oslofjord (87·12kg) than at Ims (24·42kg). Stocking of rainbow trout in fjords is feasible and may contribute to local recreational fisheries. Yield was highest when relatively small (∼50g) fish were released. Economically, the best results may be obtained when the fish are released in nutrient rich fjords.