Bohdan Draganik, Iwona Psuty-Lipska and WŁADYSŁAW Borowski
Sea Fisheries Institute, Kołłątaja 1, 81-332 Gdynia, Poland

Key words: eel fyke-net fishery, protective sieves, by-catch.

Abstract.
Three species (eel, pike-perch and bream) support the Vistula Lagoon fishery. The most prized of these is eel, which is fished with fyke-nets. The allowable minimum mesh-size for the cod-end of the net is 16 mm (bar length). This mesh size does not permit young pikeperch and bream to pass through. Depending on the place and way in which the fyke-nets are anchored and the meshes in the cod-end stretched, a considerable number of young fish are retained by the meshes. Their survival depends on many factors, the two most important of which are the time that elapses between retention and release and how the fish are manipulated by the fishermen prior to release. To prevent the premature fishing mortality of these valuable fish, fishermen fit metal sieves into the fyke-net cod-ends that permit the young fish to escape. This paper presents the results of studies on how well young pike-perch and bream escape in relation to sieve hole diameter and fish size. The examined length frequency of pikeperch and bream retained in fyke-nets covered with 6 mm mesh size netting provided the materials for assessing the number of fish that entered the net and managed to escape from it through the sieves. This paper presents the analysis of results obtained with three sieves of various hole size (18�30, 22�36, 20�65 mm).