Bulletin of the Sea Fisheries Institute 2 (141) 1997 - Selected element of the biology of ruffe (Gymnocephalus cernuus L.) of the Vistula Lagoon

Selected element of the biology of ruffe (Gymnocephalus cernuus L.) of the Vistula Lagoon
Bulletin of the Sea Fisheries Institute 2 (141) 1997, pp. 55-65

Agata Rychter
University of Gdańsk, Al. Marsz. Piłsudskiego 46, 81-378 Gdynia, Poland

Key words: growth rate, age structure, ruffe, Gymnocephalus cernuus, Vistula Lagoon.

Abstract.
The paper broadens scarce information on the biology of ruffe Gymnocephalus cernuus (L. 1758) of the Vistula Lagoon, which belongs to species prevailing in numbers in this body of water. Mean total length of fish caught by fishermen during the research period was 12.2 ą (SD) 1.6 cm, and their weight - 22.3 ą (SD) 10.6 g. Those were two- and three-year-old fish. The oldest specimen found in the analyzed material was eight years old, and the youngest under the age of one year. The ratio of males to females in the collected sample was 1:2. females reach larger sizes than males and live longer. The age determinations on scales were confirmed by the determinations on otoliths.