Conservation and recovery of freshwater fish and their rivers: a comparison of two fish indexes according to the Water Framework Directive (2000/60/EC) in a Mediterranean island

According to the European Water Framework Directive 2000/60/EC the fish fauna was investigated in 16 sites belonging to 12 Sicilian watercourses, several of which were within Sites of Community Importance and/or regional reserves and/or parks. This activity had four objectives: 1) to provide for the first time an evaluation of the ecological status of Sicilian rivers through ISECI, the fish index approved by the Italian Ministry of the Environment. 2) to compare the performance of ISECI with its updated form NISECI, which is now the reference Italian index 3) to first evaluate the reference freshwater fish communities provided by the official method approved by the Italian Ministry 4) to compare the fish indexes to other biological indexes. Five fish species belonging to three families were found: two native to Sicily, two non-native and one parauthocthonous (i.e.: introduced and established since very ancient times). The values of the two indices calculated based on the reference communities outlined in the official methodology overall showed a significantly critical situation, as no site was classified as Good or High. The study highlighted several problems concerning their application in a Mediterranean, freshwater species-poor island, the main of which was the discrepancy between the reference fish community reported in the official method and the communities really present in the island. A simulation done with “refined” reference communities revealed some differences between the two indexes. Some proposal of improvement have been outlined, like: verify, review and refine the reference fish communities; expanding the fish monitoring network; experimentation of innovative methods.