EFFECTS OF CHANNEL INCISION ON BASE-FLOW STREAM HABITATS AND FISHES

Channel incision is a widespread phenomenon that results in stream and riparian habitat degradation. Fishes and physical habitat variables w ere sampled at base flow from three incised stream channels and one re ference stream in northwest Mississippi, USA, to quantify incision eff ects on fish habitat and provide a basis for habitat rehabilitation pl anning and design. Incised channels were sampled in spring and autumn; the reference channel was sampled only in the autumn. Incised channel habitat quality was inferior to the reference channel despite the pre sence of structures designed to restore channel stability. Incised cha nnels had physical habitat diversity levels similar to a nonincised re ference channel, but contained fewer types of habitat. At base flow, i ncised channels were dominated by shallow, sandy habitats, moderate to high mean local Froude numbers, and had relatively little organic deb ris in their beds. In contrast, the reference stream had greater mean water depth, contained more woody debris, and provided more deep pool habitat. Fish assemblages in incised channels were composed of smaller fishes representing fewer species relative to the reference site. Fis h species richness was directly proportional to the mean local Froude number, an indicator of the availability of pool habitat.