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Saco, ME, United States

He P.,University of Massachusetts Dartmouth | Balzano V.,FV North Star
Fisheries Research | Year: 2011

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 14m 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 0.4kgh-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 (105kgh-1 vs. 102kgh-1, P>0.1) or the size of the shrimp (number of shrimps in 1kg, 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. © 2011 Elsevier B.V.

He P.,University of Massachusetts Dartmouth | Balzano V.,FV North Star
Fisheries Research | Year: 2012

A Nordmøre-style grid is required in many pink shrimp (Pandalus borealis) trawl fisheries in Europe and North America. However, the Nordmøre Grid does not reduce the catch of small shrimps. To reduce catch of small shrimps, a size-sorting grid with 11. mm grid spacing was developed and has been used by some trawlers. However, we do not know if the 11. mm spacing is the optimal spacing for the fishery. We thus compared two sizes of grid spacing: 9 and 11. mm. A trouser trawl system was developed and used to compare a codend with a 9. mm spacing size-sorting grid and another identical codend with an 11. mm spacing size-sorting grid. No significant differences were observed in the catch rate of shrimp, or major bycatch species between the two grids (p=0.35). The 11. mm grid caught slightly less shrimps between 18 and 22. mm carapace lengths that correspond to carapace widths of 8.5-10.5. mm. This indicates that shrimps with 8.5-10.5. mm carapace width might have escaped through the 11. mm grid, but not the 9. mm grid. These findings provide a scientific base and practical guidance for choosing grid spacing based on the size of shrimp to be released. © 2012 Elsevier B.V.

He P.,University of Massachusetts Dartmouth | Balzano V.,FV North Star
North American Journal of Fisheries Management | Year: 2012

Finfish bycatch has been drastically reduced since the Nordmøre grid became mandatory in 1992 in the Gulf of Maine trawl fishery for northern shrimp Pandalus borealis. However, the Nordmøre grid does not improve northern shrimp size selection, catching large numbers of small shrimp when they are mixed with large mature shrimp. To reduce the catch of small northern shrimp, a new dual-grid shrimp size-sorting system was developed and tested in a flume tank and at sea to evaluate its potential for reducing catch of juvenile and male shrimp in the Gulf of Maine northern shrimp fishery and to optimize rigging. These tests used a trouser trawl system consisting of one trawl leading to two separate cod ends, which compared a cod end with a dual-grid size-sorting system with another identical cod end without a size-sorting grid. The size-sorting grid had 11-mm bar spacing. The dual-grid size-sorting system significantly reduced the number of small northern shrimp with a carapace length of 22 mm or less and slightly increased catch of large shrimp with a carapace length of 23 mm or larger, when compared with the Nordmøre grid without a size-sorting grid. There was a slight reduction of northern shrimp catch rates due to the release of smaller shrimp but with no significant differences in the number or quantity of major bycatch species between the regular grid and the size-sorting grid. The new dual-grid system was practical to operate and a significant improvement over an earlier version of the size-sorting grid in design, rigging, and handling. The application may reduce small shrimp in other northern shrimp fisheries and other shrimp and prawn fisheries with suitable modification to the design. © American Fisheries Society 2012.

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