The Ecological and Conservation Status of The Guadalquivir River Basin (s Spain) Through The Application Of A Fish-based Multimetric Index

Abstract

An index of biotic integrity (IBI) based on fish health, population age-structure, abundance and community richness of native and alien fish, originally developed for the Júcar basin (E Spain) (IBI-J), was adapted and validated here for another Mediterranean basin– the Guadalquivir (IBI-G). Until now, no one fish-based IBI − sensitive, useful in a large geographical context, simple and easily applied −has been employed in species-poor Mediterranean basins. Various attempts to develop such an index have generally failed to achieve all these objectives. In this paper, the applicability of the index was enhanced through several modifications to the metrics used in the original IBI-J, and a new version of the index was also developed which included an additional metric recommended by the author of the IBI-J. In the IBI-G each of the five metrics that make up the IBI (percentage of individuals with anomalies, age structure of native fish population, relative native fish density, loss of native species and alien fish pressure) were validated and adjusted to the specificities of a typical Mediterranean fish community. Both, IBI-J and IBI-G, are robust and coherent assessment tools, highly sensitive to the main pressure gradients observed in the study area, as demonstrated by its correlation with many pressure indicators (biotic and habitat indexes, habitat variables and physico-chemical parameters). It points to the real possibility of extending the same methodology to similar basins for the purposes of monitoring, management and ecological assessment, especially in contexts relating to the Water Framework Directive (WFD). In addition, this new index does not need undisturbed reference sites, a completely unreal requisite in Mediterranean basins, where there is a general scarcity of pristine sites to be used as reference conditions. The results of this study highlight the usefulness of IBI-J/IBI-G as a powerful biomonitoring tool, especially in application of the WFD.