Analysing Dam Effects on Fish Communities in Tagus Catchment Rivers (Central Spain)

Abstract

This paper deals with the assessment of effects caused by dam water regulations on fish communities in some sites of Tagus catchment. A set of 88 electro-fishing river samples has been analysed to detect significant effects on biodiversity. Ten different indexes related to species richness and abundance, which had been already tested in Central European regions (EFI+), were calculated. By means of statistical comparison between points located upstream and downstream to dams some significant effects have been obtained. These are related to total richness and total abundance, density of intolerant species to habitat degradation, density of oxygen depletion intolerant species, richness in number of species of rheophilic reproduction habitat and density of species with lithophilic reproduction habitat. The outcomes showed that population effects depend on dam proximity and hydro-morphological traits of river reaches. In spite of the latter, density in intolerant to oxygen species, density in habitat degradation species and richness in rheophilic reproduction habitat species showed significant effects that should be imputed to dam activities.