Rope Grid: A new grid design to further reduce finfish bycatch in the Gulf of Maine pink shrimp fishery

Abstract

The pink shrimp ( Pandalus borealis) is an important commercial species for the Gulf of Maine inshore fleet with annual landings exceeding 5500 metric tons in 2010. Due to the small codend meshes used in the trawl, bycatch of juvenile finfish has been an issue. The adoption of the Nordmøre Grid since the early 1990s has significantly reduced finfish bycatch in the fishery, but a small portion of juvenile fish continues to be caught and discarded. To further reduce finfish bycatch, flume tank tests and sea trials were carried out on a radically modified Nordmøre-style grid. The new design cut away two-thirds of the netting surrounding a traditional Nordmøre Grid, and replaced the netting with four ropes, hence called “Rope Grid”. A trouser trawl with two identical codends was used for sea trials on board F/V “North Star”, a 14 m shrimp trawler, comparing the codend equipped with the new Rope Grid to the codend with a regular Nordmøre Grid. Four major bycatch species with mean catch rates greater than 0.4 kg h −1 were silver hake ( Merluccius bilinearis), red hake ( Urophycis chuss), American plaice ( Hippoglossoides platessoides) and witch flounder ( Glyptocephalus cynoglossus). The results indicate that the new Rope Grid significantly reduced all four major bycatch species by 36–50% ( P < 0.001) with no significant reduction on the targeted pink shrimp (105 kg h −1 vs. 102 kg h −1, P > 0.1) or the size of the shrimp (number of shrimps in 1 kg, RNG: 109.3 ± 1.96; ROPE: 110.0 ± 1.70; P = 0.62). The reduction of finfish bycatch was length related for all four major species with an increased rate of escape for larger fish from the Rope Grid. The Rope Grid was practical to handle and easy to modify, and has potential for adoption in this fishery as well as possible application in other shrimp and prawn fisheries around the world.