Fish movement in Relation to water temperature fluctuations in the Lower Danube river Iron gate II dam area

Abstract

Water temperature plays an important role in the fish life cycle, and have a direct impact over fish species movement behavior, migration, feeding and reproduction. The impact might be different between the rivers because of hydro morphological factors that are specific for each watercourse (sediments, water conductivity, turbidity, total suspended solids etc.). The study focuses on 3 fish species, Vimba bream (Vimba vimba), Common nase (Chondrostoma nasus), Common barbel (Barbus barbus). Total number of 43 specimens from these three fish species were caught, tagged and released in Danube River upstream and downstream the Iron Gates II dam and tracked using acoustic telemetry equipment. The fish movement was followed for eight months, from September 2019 to April 2020. In this time period, data from 26 Vimba bream, 13 Common nase and 4 Common barbel movement were collected. Acoustic telemetry data was used to evaluate fish movement in relation with the water temperature variation of the Danube River. In all three species studied, was revealed a decrease in the number of detections in the moment when the water temperature drop below 12 °C,