Role of predatory fish in community dynamics of an ephemeral stream

Abstract

In a third-order ephemeral stream in W-central Kentucky, the effects of predatory sunfish Lepomis on benthic macroinvertebrates, benthic algae, and detritivory were compared. Ambient fish densities had little effect on total macrobenthic densities and processes on lower trophic levels before intermittence. Fish modestly affected macroinvertebrate densities after intermittence, when surface exchange of prey was interrupted by sections of dry stream. Fish influence macroinvertebrates on bedrock, but not on stony, coarse substrata. Densities of two taxa were significantly affected by fish; this significantly altered the relative abundance of functional feeding groups in enclosures on bedrock by increasing the proportion of invertebrate predators in fish treatments. Macroinvertebrate densities in microhabitats on both substrata were not affected by fish presence. Dense growth of the stalked diatom Cymbella generally covered microhabitats and added structural complexity, particularly to bedrock surfaces. -from Authors