Effects of Substrate Embeddedness on Behavior of the Gilt Darter (Percina evides)
Sutherland, Andrew B.
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We investigated the general behavior of the gilt darter (Percina evides Jordan and Copeland), a benthic fish whose distribution has been shrinking since the early part of this century. Direct observations (by snorkeling) were made in Fall 1999 in five streams that differed in sedimentation, measured as substrate embeddedness. Embeddedness varied from 40% - 70%. Ten fish were observed per stream, each for 15 minutes. Observations focused on foraging, swimming, and resting as well as number of feeding strikes. Time spent foraging, swimming, and resting was significantly different (p < 0.001) among sites, as was number of feeding strikes per observation period. We also found a marginally significant (p = 0.08) relationship between foraging time and mean substrate embeddedness. Number of feeding strikes versus embeddedness was also marginally significant (p = 0.06). Swimming and resting time were not correlated with embeddedness. Mean number of feeding strikes was significantly correlated with mean foraging time (p = 0.03). This study suggests that increasing embeddedness may affect the activity of this relatively silt-tolerant darter, implying that less tolerant benthic taxa may be more heavily influenced by increasing streambed sedimentation.