New helical twine net improves efficiency and reduces bycatch

Self-spreading helical twine can improve efficiency, reduce bycatch and give fishermen access to more fishing areas.

In 2018, David Chosid of the Massachusetts Division of Marine Fisheries and Dr. Michael Pol tested a self-spreading trawl (OBT) against the older Ruhle trawl, which had become common in the bottom trawling industry for groundfish. “At the time, the haddock resource was peaking, and the idea was to develop a self-spreading trawl that fishermen could use to better target haddock while avoiding or excluding Atlantic cod and other bycatch and potentially providing access to areas closed to bottom gear,” Chosid says. The test results showed that even when bottom contact was made, the OBT could increase efficiency and reduce bycatch.

“Both nets are designed to catch haddock, not cod,” Chosid says. “The main difference is that the OBT uses a helical wire developed by the Hampiðjan Group in Iceland and is designed to be fished entirely on the sea floor.” Chosid notes that Swan Nets in Seattle has been making nets using helical wire since 2014. “They use them in the Bering Sea and West Coast hake fisheries,” Chosid says. “We wanted to see how they would perform in the northeastern United States.”

Chosid, Dr. Pol of the Responsible Offshore Science Alliance, and his team conducted four multi-day trips aboard Capt. Mark Phillips’ 72-foot trawler, the Illusion. “We tested two OBT trawls,” Chosid says. “The first trip was to tune the OBT 1, and the second was to compare its catches with the Ruhle trawl. Then, shortly after, we did two trips to tune and compare the OBT 2, which was much larger than the OBT 1.”

The team deemed OBT 2 too large for the test locations and instead focused on the test results from OBT 1. Chosid and Pol published their report in March 2023.

“The helical wire is wire wrapped around other wire,” Chosid explains. “The coils go in opposite directions on either side of the mesh, and they’re large meshes, and the hydraulic forces during the tow pull them apart.” According to Chosid and Pol’s report, 18 mm helical wire is used at the front of the net on reduced mesh sizes from 150 to 64 inches. As a result, Chosid, Pol and their company found that even with its larger opening, the OBT 1 net could be towed faster at the same revolutions per minute as the Ruhle trawl, which actually increased efficiency. “We were using gull-wing doors,” Chosid explains. “And the net-measuring technology we were using was a little outdated, so we couldn’t see exactly what the opening of the net looked like.”

Chosid notes, however, that the OBT 1 net caught significantly less bycatch than the Ruhle trawl. “The only cod we caught, and it wasn’t much, we caught with the Ruhle trawl,” he says. “With other species like monkfish, the OBT 1 caught significantly less than the Ruhle trawl, and no winter skate were caught with the OBT 1. And that’s using a slightly smaller mesh on the OBT codend (5.1 inches versus the 6-inch codend mesh used in the Ruhle trawl),” which also revealed no difference in the size of fish caught between the two nets.

However, the team struggled to completely eliminate bottom contact. Their report notes that the OBT 1 net required frequent adjustments and considerable attention to line speed and length relative to the Ruhle trawl to try to maintain the spacing of the panels and the height of the net off the bottom, noting that they relied heavily on the skill of the skipper. “The frequency of adjustments was reduced with the addition of drop chains near the wing tips,” the report says. But it adds that “sensor data, underwater video images and chain shine after release revealed evidence of a footrope that was close to or touching the bottom.” While the use of drop chains did result in some bottom contact, the team believes it was significantly reduced compared to the Ruhle trawl and that complete reduction of bottom contact is possible with more practice.

“Our results demonstrate the benefits of fishing with a helical wire OBT, even when compared to an established trawl designed to reduce Atlantic cod catches, despite the use of a small mesh size in the codend. We are optimistic that further exploration with this gear and other OBTs in various areas of Georges Bank and the Gulf of Maine, targeting species other than haddock, such as redfish, will yield more positive results.”

The exploration continues at Reidar’s Trawl Gear and Marine Supply in New Bedford, Massachusetts. Tor Bendiksen, owner of the company founded by his father, helped design the OBT nets Chosid tested, and both were made in his shop. “We based the first nets on the Ruhle trawl,” Bendiksen says. “We added the propeller and made the opening bigger. Then we tried the bigger one from Hampiðjan, but we found it covered too much of the water column, so we’re making some adjustments to make it a little more compact. And we’re working on other ideas, some of them are mine, but we have a team and we’re looking at our ideas for nets that can target fish higher in the water column, like redfish.”

Beniksen started his current project with local seafood producer Blue Harvest, but had to put it on hold after Dutch private equity firm Bregal Partners acquired a majority stake in Blue Harvest and managed it into bankruptcy. “After the Canastras bought the Blue Harvest assets, they took over and we started working on it again,” Beniksen says.

“We want to create a more maneuverable model for our boats so we can fish the bottom and move those fish up that coast,” Bendiksen says. One of the problems he and his new team are trying to solve is the design of the vessel. “They do this in Europe and Iceland – they can do it all day long. We have to work with vessels that weren’t designed for this. The pelagic trawlers in Europe and Alaska and those places have the net reels in the front, which makes it easier to make adjustments and move the weights that you need. Ours are still trawlers, with the net reel in the back, so we’re working on the design to make it easier to handle.”

In addition to the Canastra family and Bendiksen, the University of Massachusetts Dartmouth’s School of Marine Science and Technology (SMAST) is also involved in the project. “We’re fortunate to be working with Kevin Stokesbury at SMAST,” says Bendiksen, who is receiving a grant to fund much of this work. “Commercial fishermen want to do this because they know it’s what they’re going to need in the future, especially with the increase in rockfish, haddock and saithe stocks.”

While the New England fleet lags behind West Coast and European boats in adopting Hampiðjan’s self-deploying helical-wire nets, the efforts of Bendiksen, the Canastras, SMAST and other members of the Massachusetts team are expected to produce a practical version of the gear by 2025. “If we can get it off the bottom, it could open up opportunities in these closed areas as well,” Bendiksen says.