Assessing freshwater fish sensitivity to different sources of perturbation in a Mediterranean basin

Abstract

The accuracy of bioassessment programs is highly limited by the precision of the systems used to derive sensitivity-tolerance values for the organisms used as indicators. We provide quantitative support to the objective evaluation of freshwater fish species sensitivity to different sources of disturbance, accounting for co-variation issues not only between perturbations-natural gradients (especially river size), but also between different perturbations. With this aim we performed two different Principal Component Analyses , i) on a general environmental matrix to obtain a perturbation gradient independent of river size effects, and ii) on human impairment related variables to extract independent synthetic perturbation gradients. Then we checked each species responses to those gradients to assess their sensitivity-tolerance values through an available-used chi-squared analysis in the first approach and through a t-test/ANCOVA analysis in the second one. In this way we obtained sensitivity-tolerance values which could be included in future bioassessment tools, enabling effective evaluations.