ASSEMENT OF THE ECOLOGICAL STATUS OF THE CRNA RIVER BASED ON THE FISH FAUNA – CONTRIBUTION TO THE ESTABLISHEMENT OF THE MONITORING SYSTEM OF RIVERS IN R. MACEDONIA

Abstract

The purpose of this study is to assess the longitudinal variation of species composition and the community structure of ichthyofauna from the Crna River, as well as the assessment of the ecological status of the river based on the fish fauna. The investigation is made on 12 sampling points on the river during August, September and October 2006 including the reservoir Tikveš. Twenty nine species belonging to 9 families have been recorded. Among them 21 are autochthonous (native) species and 8 are allochthonous ones. The structure of fish community is evaluated by using structural indices of species richness – d, diversity H’, homogeneity – J(e) and similarity (S). Reduction of fish diversity could be noticed along the river course. It seems that changes in the habitat condition mainly associated with human activities are the main factors which alter the structure of fish community. EFI values indicate a healthy, natural or nearly natural water ecosystem or good ecological status along the river course from the source region to the sampling point T3. After the inflow of the River Blato, at the profile “Trojkrsti” (T4), the ecological status deterio- rates. The remaining downstream parts of the river has a moderate ecological status, except the profile below the town of Bitola, which according to the EFI has a bad ecological status. Below the “Skočivir” profile, the water qual- ity improves toward moderate status. The use of selected parameters of the community is found to be the effective ba- sis for further development of the system of the ecological status assessment based on the fish fauna.