Monitoring of fish species in the Senio river: distribution and morphometric measures of the populations

The aim of this work was to recognize and characterize the fish species in the Senio river, near Florence, in order to limit the loss of genetic biodiversity. These steps represent the basis for a subsequent valorisation of local species. Fish have been recognized as biological indicators for the protection of the quality of aquatic environments. In this study, monthly samplings were carried out during the year 2009 using the electric fishing on four different sites, two classified at Ciprinidae (C1 and C2 sites) and two at Salmonidae (S1 and S2 sites) according to the D.Lgs 152/2006. Data collected were used to estimate population density of each identified species using the method of consecutive passages reported by Zippin (1958). Population density measures were used to calculate the semi-quantitative Abundance Index of Moyle (AI). Morphometric measures (weight, total length, standard length, minimum and maximum circumference) and the Condition Factor (CF, weight/total length3) have been submitted to the analysis of variance considering the site as fixed effect (SAS statistical package). Barb, blageon, chub, south European nase and brown trout were collected. Chub was the most abundant species in every site considered (mean value AI 3.5). In the urban center of Palazzuolo (Firenze) city only the chub was collected, (AI 3 and CF 0.9). The most upstream site (S1) showed the greatest biodiversity (AI: Barb 3, blageon 2, chub 2, south European nase 4) presenting also a good population of brown trout (AI 2 and CF 0.9). The human impact appeared already in the S2 site localized upstream the city center in which the chub was confirmed more abundant (AI 4) than the other species which are more sensible to pollution. Nevertheless the Senio river resulted still suitable to guarantee life and development of fish populations even if the effect of human impact on water quality resulted important.