Fish stock assessment in dam reservoirs located in the upper Vistula and Warta river catchment areas based on angling catch records

The regional departments of the Polish Anglers' Association (PAA) in the provinces of Bielsko-Biała, Częstochowa, and Katowice (with a combined membership of 62,163 in 2005) stipulated that anglers keep records of catches in registers. On average, 35,682 registers were analyzed annually from 2001 to 2005, which represents 57.4% of total PAA membership. The mean annual number of the anglers recording catches in dam reservoirs was 23,231, and the average catch in this category of waters was 185 tons of fish. Of the 22 fish species recorded in the catches, six comprised 91.6% of the total catch, as follows: common carp, Cyprinus carpio (L.); bream, Abramis brama (L.); roach, Rutilus rutilus (L.); pike, Esox lucius L.; pikeperch, Sander lucioperca (L.); perch, Perca fluviatilis (L.). The share of cyprinids decreased from 73.5% in 2001 to 64.8% in 2005, whereas the share of predators increased from 18.1 to 26%, in the same time period. Carp, pike, and pikeperch were the main species in the PAA stocking programs, hence the changes observed in the species composition of the catches resulted primarily from stocking. In 2005, the maximal shares of the fish species noted were as follows: carp - 64.7% (Chechło Dam Reservoir near Chrzanów), pike - 19.8% (Dziećkowice Dam Reservoir), pikeperch - 27.8% (Tresna Dam Reservoir), bream - 72.8% (Rybnik Dam Reservoir). The results indicate that eutrophication and stocking are the main factors that determine the status of fish stocks in dam reservoirs located in the upper Vistula and Warta catchment areas.