Cel The aim of the research is to improve the selectivity of midwater trawls and thus reduce discards of nontarget species in a mixed fishery on pelagic fish, in particular concerning the combination of herring (Clupea harengus L.) with horse mackerel (Trachurus trachurus L.), mackerel (Scomber scrombrus L.) with horse mackerel (Trachurus trachurus L.), and herring (Clupea harengus L.) with mackerel (Scomber scrombrus L.). An attempt was made to improve the selectivity of midwater trawls and thus reduce discards of nontarget species in a mixed fishery on pelagic fish, in particular concerning the combination of herring with horse mackerel, mackerel with horse mackerel and herring with mackerel. Basic research on the behaviour of pelagic species to mesh barriers and mesh panels was made under laboratory conditions followed by a validation of insights resulting from this research in real fishery circumstances at sea was conducted. Flume tank experiments with barriers showed that these pelagic fish in general avoid netting panels even though they could easily pass through the relatively large open meshes. Panels with the strongest visual contrast are most effective at stimulating fish to keep clear. The shape of the meshes and the orientation of the twines also affect avoidance. A black tunnel can be used to evoke strong avoidance reactions and possibly in combination with square mesh panel or a grid section be used to separate either in size or in species. The experiment did not reveal significant differences in behaviour between the three species in a stressed situation comparable to being herded by a fishing net that can be utilised to separate them. The main conclusion of experiments on the swimming abilities was that there is unlikely to be a species separation of commercial sized mackerel, herring and horse mackerel by management or adjustment of towing speed. Observations of fish behaviour at sea show that the codend cover can have a significant effect on the escapement behaviour of fish when sloped mildly. Metal grids offer an opening to the fish that can easily be passed without changing orientation. It was evident that a configuration with grids in the top panel only is not very effective. The grids placed in an oblique way gave better results especially when a guiding panel is applied. It seems also better to cover the upgoing grid at the rear of the section with netting. Behavioral differences between species seem to play a role. A significant species separation using grids was not found.The project consists of basic research on the behaviour of pelagic species (mackerel, horse mackerel, herring) to mesh barriers and mesh panels under laboratory conditions, followed by a validation of insights resulting from this basic research in real fishery circumstances at sea. An investigation will be carried out of the distribution of fish in a mixed fishery. An experimental trawl will be designed and tested at model scale in a flume tank. This trawl will be used to investigate differences in distribution and behaviour of the species concerned. During the project the focus will shift from basic knowledge to application of selectivity enhancing devices in trawls, starting with research on the mechanical problems associated with such devices (separator panels, square mesh windows, and possibly grate systems) using scale models in a flume tank and observation of fish reactions at sea in near commercial circumstances, during which many environmental parameters will also be measured. The results will be dissipated to the national fishing industries during separate workshops improving selectivity. The effect of the size of a trawl on the species selectivity will be studied using trawls of different size. Dziedzina nauki agricultural sciencesagriculture, forestry, and fisheriesfisheries Program(-y) FP2-FAR - Community research and coordination programmes (EEC) in the fisheries sector, 1988-1992 Temat(-y) Data not available Zaproszenie do składania wniosków Data not available System finansowania Data not available Koordynator Rijksinstituut voor Visserijonderzoek (RIVO) Wkład UE Brak danych Adres Postbus 68, Haringkade 1 1970 AB Ijmuiden Niderlandy Zobacz na mapie Koszt całkowity Brak danych Uczestnicy (3) Sortuj alfabetycznie Sortuj według wkładu UE Rozwiń wszystko Zwiń wszystko Bundesforschungsanstalt für Fischerei Niemcy Wkład UE Brak danych Adres Palmaille 9 22767 Hamburg Zobacz na mapie Koszt całkowity Brak danych Scottish Office Agriculture, Environment and Fisheries Department Zjednoczone Królestwo Wkład UE Brak danych Adres Victoria Road AB11 9DB Aberdeen Zobacz na mapie Koszt całkowity Brak danych Sea Fish Industry Authority Zjednoczone Królestwo Wkład UE Brak danych Adres St Andrew's Dock HU3 4QE Hull Zobacz na mapie Koszt całkowity Brak danych
