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Postrelease Survival of Hatchery‐Reared Coho Salmon Juveniles Fed Low‐Phosphorus and Other Diets
Author(s) -
Tipping Jack M.,
Shearer Karl D.
Publication year - 2007
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/a07-001.1
Subject(s) - oncorhynchus , hatchery , biology , juvenile , zoology , phosphorus , fish <actinopterygii> , body weight , fish hatchery , fishery , aquaculture , fish farming , ecology , endocrinology , chemistry , organic chemistry
Three consecutive year‐classes of coho salmon Oncorhynchus kisutch (initial weight, ∼13 g) were adipose fin‐clipped, coded‐wire‐tagged, and divided into two groups and fed either a low‐phosphorus (0.82% P) or a standard diet (1.26% P) from October until release in April (final weight, ∼28 g). Each treatment group consisted of two raceways of 20,000 fish. The mean lengths and condition factors of fish at release were generally similar, as were feed conversion rates. Whole‐body P levels were similar at release in all groups (0.41–0.44%; wet basis). Percent retention of P was significantly greater for fish fed the low‐P diet than for those fed the standard diet in 2 of 3 years, and P discharges were reduced by a mean of 55.3% with the low‐P diet. Adult survival was similar for both groups of fish, ranging from 3.0% to 5.8%. Although no measurement was made of the availability of P, the total dietary P level (>0.77%) in the low‐P diets was sufficient for juvenile coho salmon during the freshwater phase of rearing.