Wstępne wyniki badań dotyczących liczebności sandacza, Sander lucioperca (L.) w pierwszym roku po biomanipulacji w płytkim eutroficznym jeziorze

The aim of the study was to determine the contribution of pikeperch aged 0 + (Lt <10 cm) to the ichthyofauna structure as an indicator of the reproductive success of this species in Lake Miejskie where biomanipulation was performed. The treatment was carried out in late summer 2006, and comprised stocking the lake with the predatory fish species pike, pikeperch, European catfish, and eel. Gillnet monitoring catches were performed in the lake three times before biomanipulation in 2006, and then three times throughout 2007 after it. Overall, 14 fish species were noted, including four species of predatory fish. After biomanipulation, the share of predatory fish in the ichthyofauna abundance structure increased from 3.2% to 8.9%. Before biomanipulation, pikeperch accounted for more than half of the share of predators, approximately 23% of which was 0 + pikeperch juveniles (TL10 cm). Because of the fourfold increase in the number of 0 + pikeperch individuals one year after biomanipulation, the overall share of pikeperch among predators had increased to over 91%.