Development and evaluation of a fish-based index to assess biological integrity of Mediterranean streams

Abstract

A multimetric Index of Biotic Integrity (IBI) based on fish data was developed to assess the ecological status of Iberian streams, in the context of the European Water Framework Directive. Fish assemblages were determined by electrofishing at 114 sites from 10 basins of the Júcar River Basin District. The sampled streams were typical Mediterranean streams with strong variation in flow, a species-poor and tolerant fish fauna, and low ecological specialization of the fish species. These features make it difficult to employ metrics based on species richness, trophic specialization, and reproductive strategy, which are typical of IBIs and similar indices. The proposed IBI (IBI-Jucar) is composed of five metrics related to fish health, age-structure, and abundance and richness of native and alien species. IBI-Jucar was validated by demonstrating high correlation with various measures of environmental degradation and with several biotic and habitat indices. It was also highly correlated with the European Fish Index (EFI+), despite different methods used for development and contrasting metrics obtained. The results underline the complementarity of different biotic indices and show that indices based on fish can be a valuable tool for determining environmental quality, even in species-poor Mediterranean streams