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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Expanding the Prey Base: Terrestrial vs Aquatic Prey in Predator Diets - Special Session Posters
AN ASSESSMENT OF RIPARIAN INVERTEBRATE PREY AVAILABILITY IN AN EASTERN OREGON STREAM.
C.H. Frady1, W.J. Gerth1, J.L. Li1, S.L. Johnson2, and H.W. Li3. 1Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR 97331, 2USDA Forest Service, PNW Research Station, 3200 SW Jefferson Way, Corvallis, OR 97331, 3Oregon Cooperative Fish and Wildlife Research Unit, Oregon State University, Corvallis, OR 97331
We compared prey availability for rainbow trout (Oncorhynchus mykiss) using three techniques: pan traps, drift nets, and beating sheets placed under riparian vegetation in a third-order, birch riparian stream reach. These methods assessed prey sources from the water column, water surface, and riparian vegetation. We observed differences in relative abundances and species composition among collection techniques over a 48 h interval. Aquatic and terrestrial invertebrates collected in pan traps exhibited temporal variations over 12 and 24 h. Slight differences in collection dates resulted in large differences in species composition, probably related to pulses of emerging insects. Adult stoneflies were abundant in riparian shrubs but not collected in pan traps. A hatch of tipulid flies captured in pan traps was not detected in other methods. Fish diet, determined by stomach lavage, revealed a higher proportion of glossosomatid caddisflies than predicted by availability in invertebrate samples. Our preliminary comparisons suggest that ideally, concurrent sampling of invertebrates and fish consumption is needed to estimate prey electivity.
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