The effects of recreated instream and ecotone structures on the fish fauna of an epipotamal river

Studies carried out between 1981 and 1984 on 15 stretches of 7 Austrian epipotamal streams provided data on the effect of river bed structures on fish communities. River straightening reduced spatial heterogeneity, resulting in a reduction of species abundance, diversity, stock density and biomass. A subsequent project which restructured cross section, bottom and shorelines with the introduction of groynes and bedfalls improved all fish communities during a period of investigation between 1988 to 1990. The restructuring provided refuge areas during flooding and nursery grounds for fish fry. The surrounding landscape was not altered. The benefits of the recreated land and water ecotone are discussed with regard to river restoration projects.