Bycatch is a persistent issue in the North Sea brown shrimp (Crangon crangon) fisheries, where bycatch reduction devices are insufficient at excluding juvenile fish. Growing ecological concerns and management pressures necessitate more effective separation of brown shrimp and bycatch in these fisheries. Quantitative knowledge of species vertical distributions within trawls can be used to optimize existing bycatch reduction devices or to develop alternative concepts. This study aimed to quantify the vertical distribution of brown shrimp and commercial fish bycatch using a beam trawl whose aft section was vertically split into four equal height compartments. Length-based modeling was applied to more than 35,000 brown shrimp and vertical distribution indicators were calculated for commercial fish bycatch species. Brown shrimp were predominantly caught in the bottom two compartments of the trawl (undersized: 73.4%, marketable: 75.7%), whereas whiting (Merlangius merlangus), common dab (Limanda limanda), sandeels (family Ammodytidae), and plaice (Pleuronectes platessa) were predominantly caught in the upper two compartments (74.6%, 67.7%, 67.6%, 74.5%, respectively). These results support investigating the use of sorting grids with upper escape openings as well as behaviour-based separation strategies with stimulus devices. Results and implications should be validated across a wide range of environmental and operational conditions.
promotor/supervisor feedback
nothing yet
