Effects of lowhead dams on riffle-dwelling fishes and macroinvertebrates in a midwestern river

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dams, habitat, upstream, Substrate, species richness

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Transactions of the American Fisheries Society


Many studies have assessed the effects of large dams on fishes andmacroinvertebrates, but few have examined the effects of lowhead dams. We sampled fishes,macroinvertebrates, habitat, and physicochemistry monthly from November 2000 to October 2001at eight gravel bar sites centered around two lowhead dams on the Neosho River, Kansas. Sitesincluded a reference site and a treatment site both upstream and downstream from each dam.Multivariate analysis of variance indicated that habitat, but not physicochemistry, variedimmediately upstream and downstream from the dams, with resultant effects onmacroinvertebrate and fish assemblages. Compared with reference sites, upstream treatmentsites were deeper and had lower velocities and downstream treatment sites were shallower andhad higher velocities; both upstream and downstream treatment sites had greater substrate compaction than reference sites. Macroinvertebrate richness did not differ among site types, butabundance was lowest at downstream treatment sites and evenness was lowest at upstreamtreatment sites. Fish species richness did not differ among site types, but abundance was highestat downstream reference sites and evenness was highest at upstream sites. The abundance ofsome benthic fishes was influenced by the dams, including that of the Neosho madtom (Noturusplacidus), which was lowest immediately upstream and downstream from dams, and those of thesuckermouth minnow (Phenacobius mirabilis), orangethroat darter (Etheostoma spectabile), andslenderhead darter (Percina phoxocephala), which were highest in downstream treatment sites.Although limited to one system during a 1-year period, this study suggests that the effects oflowhead dams on fishes, macroinvertebrates, and habitat are similar to those reported for largerdams, providing important considerations for riverine ecosystem conservation efforts.





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