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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Fish Ecology II
STREAM ECOSYSTEM RESPONSE TO INCREASED LIGHT AND SALMON CARCASS INTRODUCTION.
M.A. Wilzbach1, B.C. Harvey2, K.W. Cummins1, O. Hernandez3, and H. Ambrose1. 1California Cooperative Fish Research Unit, Humboldt State University, Arcata, CA 95521USA, 2USFS Redwood Sciences Laboratory, Arcata, CA 95521USA, 3Department of Entomology, Michigan State University, East Lansing, MI 48824 USA
We are conducting a split-plot field experiment to evaluate the relative effects of increased light together with nutrient enhancement from salmon carcasses and riparian litter on salmonid growth and the structure of the food web pathways that support salmonid production. In each of six streams in the Smith and Klamath River basins in northern California, a 20-m wide band of riparian hardwoods was removed along both streambanks of a 100 m reach to increase incident radiation. A second 100 m reach, with an intact canopy, was established in each stream to serve as a light control. In three of the six streams, salmon carcasses, at a density of 1 carcass/2m of stream, were added to both canopy-pruned and light-control sections. Pre-treatment stream reaches were similar in nutrient concentrations, chlorophyll-a, macroinvertebrate functional group composition, and in fish composition. In canopy-removed sections, litter inputs and shredder representation decreased and cumulated PAR increased dramatically, with an attendant increase in primary production. Data are being collected to test the hypothesis that fish growth will be greatest in lighted, nutrient-enhanced reaches, and will decrease in order of lighted reaches without nutrient enhancement, shaded reached with nutrient enhancement, and shaded reaches without nutrient enhancement.
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