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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Life Histories
CADDISFLY GROWTH IN RESPONSE TO SPRING CARRY-OVER OF MARINE-DERIVED NUTRIENTS FROM SPAWNING SALMON IN ALASKA.
J.L. Lessard1, R.W. Merritt1, and K.W. Cummins2. 1Department of Entomology, Michigan State University, East Lansing, MI, USA 48824, 2California Cooperative Fisheries Unit, Fisheries Department, Humboldt State University, Arcata, CA 95521
Studies investigating enrichment effects from spawning salmon, termed marine–derived nutrients (MDN), have shown the stimulation of production in stream communities including algae, invertebrates, and fish. We investigated the effect of MDN on the growth of three trichopteran genera (Dicosmoecus, Onocosmoecus, and Psychoglypha) in an anadromous stream above and below a waterfall barrier. Caddisflies were collected in May, during which a subsample of each genus was measured for total length and dry weight. Individuals were placed into growth boxes (Tupperware® with plastic mesh replacing cut-out sides) so that each box contained individuals of two genera. Insects taken from below and above sections were placed in boxes both below and above the waterfall. Conditioned leaves and algae on rocks provided food. The boxes were tethered into small pools for a month and then removed. Some larvae from all genera were lost, but Dicosmoecus larvae were most commonly missing from the boxes. Lengths and dry weights were obtained for all individuals remaining and from another subsample from the stream. Size frequency histograms revealed differences between stream insects and those grown in the boxes as well as differences in growth among genera. Preliminary results did not indicate larvae grew differently between stream sections.
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