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Changes to Rainbow Trout Abundance and Salmonid Biomass in a Washington Watershed as Related to Hatchery Salmon Supplementation
Author(s) -
Pearsons Todd N.,
Temple Gabriel M.
Publication year - 2010
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/t08-094.1
Subject(s) - rainbow trout , chinook wind , hatchery , oncorhynchus , fishery , biomass (ecology) , trout , salmo , biology , zoology , salmonidae , abundance (ecology) , fish measurement , ecology , fish <actinopterygii>
We evaluated the changes in (1) the abundance, size, and biomass of rainbow trout Oncorhynchus mykiss , (2) the abundance of spring Chinook salmon O. tshawytscha parr, and (3) the combined biomass of rainbow trout and Chinook salmon parr after nine annual releases of approximately 250,000 Chinook salmon and coho salmon O. kisutch smolts into the North Fork of the Teanaway River, Washington. The trout and salmon were sampled in two treatment locations consisting of five sites and three control locations consisting of seven sites before (1990–1998) and during hatchery releases (1999–2007). We detected statistically significant decreases of rainbow trout abundance and biomass in both treatment streams relative to two of the three control streams. Furthermore, all of the differences in abundance between treatment and control streams were in the negative direction. All but one of the differences in biomass was negative. The only statistically significant change in the combined biomass of spring Chinook salmon parr and rainbow trout before and during supplementation was negative, and five of the six differences in combined biomass were negative. Only one of the four comparisons of the ratio of the log‐transformed weight to length of rainbow trout was statistically significant, and it decreased during supplementation; one‐half of the comparisons were positive and the other half negative. The changes to rainbow trout abundance and biomass were probably the result of the cumulative impacts from hatchery‐released Chinook salmon smolts and an increase in naturally produced Chinook salmon parr.