Ichthyofauna of the rivers in the Romincka Forest (Pregola River basin, northeastern Poland)

The composition and structure of the ichthyofauna of the rivers of the Romincka Forest (Pregola River basin, northeastern Poland) was investigated. Twenty-two fish species were confirmed to occur, four of which are protected: bullhead, Cottus gobio L.; spined loach, Cobitis taenia L.; bitterling, Rhodeus sericeus (Pall.); stone loach, Barbatula barbatula (L.). Species richness was the highest in the Bludzia River, in which 17 fish species belonging to 6 ecological reproductive guilds were confirmed. The ichthyofauna of the other rivers in the forest generally comprised 6-10 fish species belonging to 4-5 ecological reproductive guilds. The number of fish occurring at sampling sites decreased with increased river gradient, while the number of rheophilic species increased.