Shrimp Separator Trawl Experiments: Gulf of Maine Shrimp Fishery
design, Gulf of Maine, horizontal, juvenile, mesh, mortality, Nordmore Grate, shrimp, structures
The discard of finfish bycatch in the Gulf of Maine, northern shrimp trawl fishery is considered a serious problem. The species specific discard rate varied from 17% for winter flounder to 95% for silver hake in fifty tows made by commercial trawlers during the period 1985-1989 (Howell and Langan, 1990). Studies by Jean (1963) and Howell and Langan (1987) suggest a very high mortality for discarded finfish in the Western North Atlantic fisheries. The discard problem has two major facets: direct wastage in throwing back fish into the sea and loss of future catches of larger animals through the mortality of small individuals (Saila 1983). Given the perceived problem of discarded bycatch in the Gulf of Maine shrimp fishery, the objective of this project was to experiment with several design modifications to existing traditional trawls that would reduce the juvenile finfish bycatch. The concept of selective shrimp trawls is not novel. Trawl design modifications have been evaluated in shrimp fisheries to separate the finfish from the shrimp with varying success. The techniques utilize behavioral and size differences between shrimp and finfish, and include horizontal separator twine panels, large mesh escape panels, deflecting grids, accelerator funnels, and others. In this project, the northern style shrimp trawls served as the control nets. The basic modifications evaluated were: large mesh in belly area and a funnel accelerator ahead of the trawl cod-end.