Changes in whitefish (Coregonus lavaretus L.) and vendace (Coregonus albula L.) fisheries in Lake Goldopiwo due to eutrophication and management policies

Whitefish (Coregonus lavaretus L.) was introduced (probably from Lake Peipus) into Lake Goldopiwo, NE Poland, at the end of the nineteenth century. From 1922 to 1934, the lake constituted a basic source of the stocking material for numerous lakes of the region. Lake Goldopiwo became one of the three Polish lakes with the highest landings and yields of whitefish. In 1951-1995, the average annual catch was 4778 kg (5.54 hg ha(-1)), and was as much as almost 18 % of the total catch. At thr same time, the average annual catch of vendace was 1750 kg (2.0 kg ha(-1)). In recent years, especially in the 1990s, catches as well as the effectiveness of whitefish and vendace stocking has declined dramatically. This has been coupled with an increase of cyprinids' share, reflecting changes in the fish stocks caused by lake eutrophication. The paper presents the history of coregonine management in Lake Goldopiwo from 1951 to 1995, with attention paid to the changes in the effectiveness of whitefish management on the background of eutrophication, changes in the catches of other fish species, and the most important managerial factors.