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The Effects of Stock and Prerelease Marine Net‐Pen Culture on Survival to Adulthood, Age at Maturity, and Fisheries Contribution for Three Stocks of Chinook Salmon in Southeast Alaska
Author(s) -
Thrower Frank,
Joyce John E.
Publication year - 2006
Publication title -
north american journal of aquaculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 41
eISSN - 1548-8454
pISSN - 1522-2055
DOI - 10.1577/a05-027.1
Subject(s) - fishery , chinook wind , biology , hatchery , oncorhynchus , juvenile , stock (firearms) , broodstock , fish stock , aquaculture , fishing , ecology , fish <actinopterygii> , geography , archaeology
Three stocks of juvenile stream‐type Chinook salmon Oncorhynchus tshawytscha were evaluated as part of an ocean ranching and broodstock development program at Little Port Walter, Southeast Alaska. Fish were either cultured in freshwater throughout the presmolt period or moved to marine net‐pens with an artificial freshwater lens for five periods (2–210 d); all fish were released on the same day. The fish were tagged with coded wire tags to determine the effect, if any, of stock and duration of marine net‐pen culture on precocity, fishery contribution, survival to adulthood, and size in the commercial fisheries relative to traditional freshwater culture. Recoveries of tagged fish in the fisheries and at the hatchery weir indicated significant overall effects of stock on marine survival; the Unuk stock survived better than the Chickamin and King Salmon stocks. Culture overwinter in marine net‐pens produced higher survival to adulthood in all stocks but also resulted in higher mortality during culture and a higher proportion of precocious males in one of the stocks. The effects of short‐term spring net‐pen culture on juvenile Chinook salmon also varied by stock. Unuk and Chickamin stocks cultured for short periods in marine net‐pens generally had higher survival to adulthood, similar fishery contribution, and similar precocious maturation rates as their respective freshwater controls, while the King Salmon stock experienced variable marine survival, precocity, and fishery contribution rates. For facilities with limited freshwater or a limited number of fish to release, the use of marine net‐pens for short‐term culture could help reduce densities, ease rearing space constraints, and maximize adult production. These benefits appear to have stock‐specific limitations.