River degradation impacts fish assemblages in Kosovo’s Ibër basin

Abstract

Fish sampling was conducted in 20 sites within the Ibër River and its tributaries in Kosovo (August 2023) collecting 23 taxa (1674 individuals) through a standardized electrofishing protocol. Relevant physico-chemical measurements and anthropogenic pressures were collected and analyzed with respect to the ichthyological data of the surveyed sites. The survey represents a rapid assessment procedure, limitations and prospects of the effort are described. Several attributes of the fish assemblages showed severe degradation, characterized by low population densities, low species diversity, minimal reproductive evidence and the absence of several sentinel species. Multiple anthropogenic pressures have severely modified the fish communities over a wide area; pollution, barriers to movement and hydroelectric dams stand out as important drivers of degradation. Only two fish species showed some level of tolerance to heavily polluted waters (Carassius gibellio, Rutilus rutilus). Low fish population densities were also correlated with various forms of hydromorphological degradation. Only Barbatula barbatula, Phoxinus sp. and Lepomis gibbosus had proportionately higher population densities in areas where impoundments and power-station dam hydropeaking were severe. In this regard, conservation actions are urgently needed.