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Survival of Rainbow Trout during Their First Winter in the Henrys Fork of the Snake River, Idaho
Author(s) -
Smith R. W.,
Griffith J. S.
Publication year - 1994
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1994)123<0747:sortdt>2.3.co;2
Subject(s) - cobble , rainbow trout , predation , fishery , fish measurement , biology , fish <actinopterygii> , salmo , trout , zoology , environmental science , ecology , habitat
To evaluate their first‐winter survival, wild rainbow trout Oncorhynchus mykiss (78–169 mm total length) were placed in small wire‐mesh cages at four sites along a thermal gradient in the Henrys Fork of the Snake River in October 1989. Four cages at each site contained cobble rock cover and four had no cover. Our hypotheses were that test fish would have better survival if cover were available or if water temperatures were higher at the site, and that larger fish would have better survival than the smaller fish of the test group. Survival ranged from 100% at a spring‐fed site to 63% at the coldest site. In the cages checked periodically, 95% of the mortality occurred during early winter and no mortality occurred during late winter. Survival was 11–24% higher in cages with cover than in those without cover; and was higher for larger fish than for smaller ones. Fish smaller than 100 mm in October did not survive the winter. Water temperature in spaces among cobble rock cover in the cages was 0.2–1.0°C higher throughout winter than in the overlying water. Survival rates of the test fish in the colder sites were probably higher than those of free‐living wild fish in the study area because the cages protected test fish from predators and shifting ice.