WŁADYSŁAW Borowski, Henryk DĄBROWSKI  and Ryszard Grzebielec
Sea Fisheries Institute, Kołłątaja 1, 81-332 Gdynia, Poland

Key words: eel, Vistula Lagoon, tagging, migrations, growth, mortality, biomass.

Abstract.
In 1994, 5,042 specimens of eel  were tagged with external Floy Tags in the Vistula Lagoon. The results of tagging were elaborated based on tag recoveries from July 1994 through October 1995. During tag collection, performed solely at the ports of the Vistula Lagoon, the method of multiple release (after recording the data) of live eel delivered with tags was applied. A total of 22% of tags were recovered at first capture. The largest number of recoveries (1,096 tags) was obtained from the fishing grounds of the Vistula Lagoon, out of which 1,086 tags were obtained from the Polish, and 10 from the Russian, part of the lagoon. By comparison, in the Baltic seven tagged eel were captured, including five in the Danish waters, and one in the German and Swedish waters each. The eel tagged in the spring migrated mainly into deeper waters, toward the Piława Strait. During the first three days after tagging these eel were captured at a distance of 2 do 15 km from the place of release. By contrast, the eel tagged in the fall migrated primarily into coastal waters. Mean length and body weight increments of the tagged eel caught in 1995, as compared with the eel released in 1994, equaled 5.4 cm and 79.8 g, respectively. Upon calculating the mortality coefficients, von Bertalanffy growth equation parameters and biomass of the population, the following values were obtained: Z = 1.56, F = 1.0, M =0,.56, L_nif = 75-163 cm, K = 0.04 and B = 395 t.