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Proportions of Hatchery‐ and Naturally Produced Steelhead Smolts Migrating past Rock Island Dam, Columbia River, Washington
Author(s) -
Peven Charles M.,
Hays Steven G.
Publication year - 1989
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8675(1989)009<0053:pohanp>2.3.co;2
Subject(s) - hatchery , salmo , fishery , rainbow trout , fish <actinopterygii> , fish hatchery , oncorhynchus , biology , environmental science , fish farming , aquaculture
Proportions of hatchery‐ and naturally produced fish contributing to the outmigrant run of steelhead smolts Oncorhynchus mykiss (formerly Salmo gairdneri ) were estimated from data collected at the Rock Island Dam bypass trap between 1 April and 30 June 1986. Hatchery fish, which averaged 28 mm longer than naturally produced fish, made up 72.5% of the run. Two methods were used to estimate the total run size. One was the “life history” method based on the number of spawning adults and survival rates; the other was the Petersen mark–recapture method in which hatchery fish with clipped adipose fins formed the marked group. The two resulting estimates were 904,689 and 904,729 fish, respectively. Sensitivity analyses were performed on variables that affected the natural production and total run size estimates. The analysis suggested that estimates of mortality related to dam passage and egg‐to‐smolt survival have the greatest effect on the run size estimations.