Efectes de l’alteració hidrològica en les comunitats de macroinvertebrats i en la dieta de les poblacions de barb de muntanya en la Llémena

The hidrological intermittence is a common perturbation in Mediterranean rivers which dry out during summer forming isolated puddles between them. The construction of dams can cause that a river, which previously had a permanent flow, becomes intermittent in some of its sections. This type of perturbations cause changes in the communities which live associated with the aquatic ecosystems. Macroinvertebrates are important indicators of the condition of these ecosystems because they are really sensitive to perturbations. Modifications of macroinvertebrates communities can cause several changes in the predator fish’s diet, which can see themselves obligated to feed on less nutritious preys. In order to evaluate this effect, macroinvertebrates comunities and the diet of the mountain barb (Barbus meridionalis) have been studied in two sections separated by a dam that causes intermittent hydrological periods down the Llémena stream. Several differences have been found in biomass and abundance of the macroinvertebrates communities and in the abundance of the mountain barb in both sections, but differences haven’t been found in the composition of its diet. This study demonstrates that the presence of the dam has a clear effect on the macroinvertebrates community as well as to the density of mountain barbs. However, the barb’s diet is not affected because it feeds mainly on chironomidae larvae, which were really abundant in both section