The species composition and biomass of the fish passing through the chamber fishway located in the Rożnów Reservoir dam in the fall, spring, and summer was determined. Fish samples were collected by electrofishing in the resting chamber. The numbers of other species were estimated in the remaining chambers. In the 1997-2003 period the presence of seventeen species was recorded. The decided dominant was bleak, which comprised 79.2% of all fish at 28362 specimens. Cyprinids comprised 98.8% of all the fish examined. Significant variations were observed in the abundance of fish in particular years and seasons. Fish from older year classes passed through the fishway. Only common bream, barbel, and possibly bleak were undertaking spawning migrations. Only three sea trout specimens were observed in the study period. In order to gain a complete picture of the fish passing through the fishway, monitoring should be conducted on a permanent basis.
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