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Commercial Fisheries News
Volume 34 Number 6
February 2007
UNH net uses ropes to separate haddock, cod
This is the fourth installment in our ongoing series examining the performance of various haddock net designs that fishermen and scientists around the region have been testing in cooperative research projects.
The goal is to find a net that New England fishermen can use to target abundant haddock stocks while avoiding low-quota species, especially cod and yellowtail.
Here, University of New Hampshire researchers Pingguo He and Tracey Smith describe the field test results of a “rope separator haddock trawl” designed by He with the assistance of Harold Delouche of Memorial University of Newfoundland. Trawlworks Inc. of Narragansett, RI built the prototype trawl. –Editor
DURHAM, NH – Pingguo He of the University of New Hampshire and fisherman Carl Bouchard of Exeter recently collaborated on a project to test a rope separator haddock trawl in the Gulf of Maine.
The goal of the project was to design a net that would catch haddock and pollock while allowing cod and other bottom species such as flounders and lobsters to escape, which would allow the net to be used to fish for haddock in a B-days-at-sea program.
A unique feature of the new trawl is the use of ropes instead of netting to create the horizontal separator.
The project was funded by the Northeast Cooperative Research Partners Program (NCRPP) administrated by the National Marine Fisheries Service and was a true joint effort between the industry partner and the University of New Hampshire.
The design and rigging of the trawl was tested in the flume tank at the Centre for Sustainable Aquatic Resources (CSAR) of the Memorial University of Newfoundland in Canada in December 2004 with the assistance of Harold Delouche and Paul Winger of CSAR. Trawlworks Inc. of Narragansett, RI manufactured the full-scale gear.
Sea trials took place on board Bouchard’s Stormy Weather during the springs of 2005 and 2006 on Jeffreys Ledge in the Gulf of Maine. The majority of the tows made in 2005 and some of the early tows in 2006 were used to make adjustments to the gear. Eighteen pairs of comparison tows were made in 2006, with the last 10 pairs of tows producing commercial quantities of haddock in the catch.
Design, specifications
The design of the rope separator trawl makes use of behavior differences between haddock and other groundfish species, particularly cod. The trawl has a high vertical opening to prevent haddock from escaping upwards over the headline. Cod tend to stay relatively near the bottom when exhausted from swimming with the trawl.
The design includes a four-panel trawl structure to increase headline height. The separator panel is a series of parallel ropes 6'-9' off the seabed.
A large exit opening at the bottom of the trawl allows cod, flounders, and other bottom-dwelling fish and shellfish species to escape.
The commercial trawl used for comparison as a control was a 286-mesh x 6" balloon trawl commonly used in the inshore Gulf of Maine multispecies fishery.
Both experimental and control trawls had identical 6-millimeter diameter, double-polyethylene twine, 6-1/2" mesh size codends with chafing materials. The codend was 46 open meshes round and 25 meshes long. Both gears had the same bridle length of 180' and an identical 12" rubber disc (floppy) sweep. They were towed at the same speed of 3.1 knots.
Fish behavior and rope position were recorded using an underwater camera system. Netmind sensors and Star-Oddi tags were used to measure the geometry of the gear.
Results
The rope separator haddock trawl was easy to operate and required no special deck machinery and no additional crew to deploy or retrieve. The ropes were easy to adjust and replace if required, though none of the ropes needed replacement due to breakage during the trials.
A big advantage of using ropes rather than a mesh panel to separate the fish was that fish were not “meshed” or stuck between the ropes. The ropes also were able to increase the separation efficiency of the net since fish that were in the upper or lower parts of the codend were able to swim through the ropes.
Cod were seen on the video recordings swimming down and haddock were seen swimming up through the ropes.
Commercial rates of haddock – 579 pounds per hour for the control net and 464 pounds per hour for the experimental trawl – were caught during the last 20 tows in 2006.
The average number of cod caught during these tows was reduced from 30 to 12, a reduction of 65%. The number of haddock caught was also reduced slightly in the experimental net from 146 to 123, a 16% reduction. The catch of flounders for the control and for the experimental trawl was 50:1. The catch in yellowtail flounder was 83:1.
Conclusions
The rope separator haddock trawl proved to significantly reduce cod catch with a slight reduction in haddock catch. The new gear reduced and sometimes eliminated other species commonly associated with commercial multispecies trawls, such as flounders, dogfish, lobsters, and skates.
The ability of the new trawl to eliminate the catch of yellowtail flounder could reduce the impact of haddock harvesting on the yellowtail stock, which is depleted in the New England area.
The fishing grounds and season were deliberately picked so that a good mix of cod and haddock could be caught to demonstrate the separation abilities of the gear. If the new rope separator haddock trawl is used in known “haddock spots,” the cod-to-haddock ratio could be reduced to a much lower level and meet the requirements for the Eastern US/Canada Haddock Special Access Program.
We are looking into opportunities to test similar designs on Georges Bank to explore the possibility of using the design in that area to harvest abundant haddock resources while conserving cod and yellowtail flounder.
Pingguo He
Tracey Smith
Pingguo He is a research associate professor of fisheries at the Ocean Process Analysis Laboratory of the Institute for the Study of Earth, Oceans, and Space at the University of New Hampshire and a commercial fisheries extension specialist at New Hampshire Sea Grant. Tracey Smith is a research technician in He’s group.
For more information on the rope separator haddock trawl or on other fishing gear issues, call He at (603) 862-3154 or e-mail him at <pingguo.he@unh.edu>.
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