A new shrimp trawl combination grid system that reduces small shrimp and finfish bycatch

The Nordmøre Grid developed more than twenty years ago has significantly reduced finfish bycatch in the northern shrimp (Pandalus borealis) fishery in Europe and North America. However, the grid does not reduce the catch of small shrimp and juvenile fish that are able to pass through the spaces between grid bars. A comprehensive project was initiated to reduce finfish discards and small shrimp in the Gulf of Maine northern shrimp fishery. The project designed, tested, and optimized a size-sorting grid ( He and Balzano, 2012a and He and Balzano, 2012b) and a radically modified Nordmøre-style grid (the Rope Grid, He and Balzano, 2011). These previous papers reported the results of the separate designs (either size-sorting grid or the Rope Grid). This paper reports performance of a combination grid in a shrimp trawl consisting of a 9 mm spacing size-sorting grid and a Rope Grid. The combination grid (9Rope) reduced both small shrimp and finfish bycatch when compared to a regular Nordmøre Grid (RNG). The new combination grid reduced finfish bycatch by 33%, with a small reduction of targeted shrimp catch (12%). The finfish reduction was length-related for three of the above four species with greater reductions for larger individuals. The combination grid is practical to handle and has potential for commercial use in the northern shrimp fishery in Gulf of Maine and other regions where similar target and bycatch species are mixed.

► Successfully designed a new species and size selection combination grid.
► The new combination grid reduced finfish bycatch and small shrimp.
► Major finfish bycatch reduction ranged from 29 to 53%.
► A greater number of larger finfish individuals were reduced in the bycatch.
► The combination grid was easy to use and handle with existing deck machery.