A multimetric index based on fish fauna for the evaluation of the biotic integrity of streams at a mesohabitat scale

Abstract

AIM: In this study, we evaluated the ability of the Index of Biotic Integrity (IBI), based on fish fauna, to discriminate between reference streams and degraded streams at a mesohabitat scale. METHODS: We sampled the ichthyofauna of 96 mesohabitats (runs, riffles and pools) with electrofishing gear in six streams (three reference and three degraded) of comparable volume, width, and depth. Twelve attributes were tested separately for different mesohabitat types. RESULTS: Ten of the metrics tested were used to obtain the IBI for runs, six for riffles and ten for pools. The IBI indicated poor conditions for runs and riffles and very poor conditions for pools. CONCLUSIONS: These results indicate that the IBI may be useful for distinguishing among environments with contrasting conservation status at a mesohabitat scale. Differences were obtained not only in the sets of metrics valid for each mesohabitat but also in the final scores and rankings of the mesohabitat types assessed. These results emphasize the importance of considering the structural and biological variability of aquatic environments to capture the significance of losses of integrity due to human influence.