Retrospective analysis of current state of the ichthyofauna of the Vilshanka and Tiasmyn river basin

Trends in fish fauna of the Vilshanka and Tiasmyn river basin within the last 50 years have been analysed. Current ichtyofauna of the Vilshanka River basin is composed of 21 species seven of which (Pseudorasbora parva, Barbatula barbatula, Pungitius platygaster, Gasterosteus aculeatus, Syngnathus abaster, Babka gymnotrachelus and Perccottus glenii) are recorded from this region for the first time. The Tiasmyn River basin yiel­ded 22 fish species five of which (Misgurnus fossilis, Pungitius platygaster, Gasterosteus aculeatus, Gymnocephalus cernuus, Proterorhinus semilunaris) are recorded for the first time. Including historical records, the number of recorded fish species is 35 and 26 for the Vilshanka River basin and the Tiasmyn River basin, respectively. The fish species composition of the Vishanka River basin and the Tiasmyn River basin has altered over the time in 60 and 43 %, respectively. The present study highlights the importance of the oxygen regime in a water flow, introductions and presence of necessary habitats for the fish species distribution, whereas the general mineralization of water (GM), pH and temperature regime does not directly affect the fish distribution.