Impact of the Włocławek dam on migratory fish in the Vistula River
The aim of this paper is to summarize knowledge concerning the decline of vimba, Vimba vimba (L.) and sea trout, Salmo trutta m. trutta L. populations in the Vistula River following damming and the effectiveness of measures undertaken to counteract this and rebuild fish stocks. The assessment of the fish pass at the Włocławek Dam was done using both the conventional method of counting all the fish entering the fish pass and a new one based on data obtained with a special trap that permitted counting only the fish that had reached the top chamber of the fish pass (i.e., those that actually passed through it). Completed in 1968, the Włocławek Dam on the Vistula is located 266 km from the river mouth. A conventional pool fish pass was constructed in the dam in 1970. However, this measure was ineffective, and the dam prevented the upstream migration of vimba and sea trout. In order to minimize the negative effects of damming on the vimba population, the unconventional method of transporting spawners was applied in the 1970s and early 1980s. Despite promising results, this experiment of transporting spawners was discontinued in 1982 due to a lack of funding. The results of this experiment are summarized in the present paper, and similar methods are proposed for the future restoration of the vimba population in the Vistula River. Restoration programs for salmon, Salmo salar L. sea trout, vimba, and sturgeon, Acipenser oxyrinchus Mitchill, are currently in development in Poland. On the Vistula River the Włocławek Dam is the main obstacle that prevents them from being fully successful.
Wiesław Wiśniewolski, Instytut Rybactwa Śródlądowego, Zakład Rybactwa Rzecznego, ul. Główna 48, Żabieniec, 05-500 Piaseczno, Tel./Fax: +48 (22) 7562044; +48 (22) 7562088; e-mail: firstname.lastname@example.org