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Presented at the NABS Annual meeting, Athens, Georgia, 2003
in Community Ecology II
The best place to eat: food availability vs. predation risk in lotic crayfish habitat selection
C.A. Flinders1 and D.D. Magoulick2. 1Patrick Center for Environmental Research, The Academy of Natural Sciences, Philadelphia, Pennsylvania 19103, 2Arkansas Cooperative Fish and Wildlife Research Unit, Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701
Optimal foraging theory predicts that in a patchy environment, foragers occupy patches with the greatest rate of energy intake. However, predation risk often results in habitat selection offering diminished foraging yields but greater protection from predators. In the Warm Fork River (Oregon Co., MO), crayfish differentially utilize stream habitats by size with greater densities of small crayfish in shallower habitats and large crayfish in deeper habitats. We examined resource availability (macroinvertebrates, detritus) and predation risk (tethering experiments) of small and large crayfish (Orconectes marchandi) in shallow (<30 cm) and deep (>55cm) stream habitat. An enclosure experiment with replicate blocks containing a single large crayfish, small crayfish, and no crayfish determined size– and habitat– related foraging profitability (growth). Macroinvertebrate biomass was significantly greater and detrital biomass significantly lower in the shallow than deep habitat. Crayfish predation rates were significantly greater in the deep than shallow habitat but independent of crayfish size. Growth rates were significantly greater for small crayfish than large, but were not habitat-dependent. Large crayfish significantly reduced levels of silt, chlorophyll a, and AFDM on tiles in enclosures relative to small and no crayfish treatment, and this effect was habitat–dependent. Results indicate an interaction between resources and predation risk in crayfish habitat selection.
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