Among the many exhibitors at the November 2024 Pacific Marine Expo in Seattle, the Norwegian company Mørenot showcased its electric longline system and trawl doors and introduced its new Injector Flow Gear, a trawl sweep intended to replace rock hopper sweeps for fishing on hard bottom.

“The rock hopper gear is getting harder to find because of the war,” says Haraldur Arnason, Mørenot’s head of trawl systems. “A lot of the material originates in Russia and Ukraine.”

But scarcity of the rock hopper gear is not the main reason Mørenot developed the Flow Gear. Arnason notes that there are issues with operating rock hopper gear, and the company wanted to develop a product that would address those. “With the rock hopper, when it goes over a rock it flies off bottom and stays up long enough for fish to get under the net,” he says. “Or sometimes it flips the rock inside the net and then it tears the net.”

To resolve that problem, Mørenot’s Flow Gear is made of pieces of hard plastic shaped like half tubes, and these flip up over rocks and enable the sweep to stay close to the bottom. “Each piece is 2 feet wide and 18 inches deep,” says Arnason. “They hang from a chain footrope and are chained together. Some were breaking when we first designed them, then we added three pieces of steel horizontally along the lower edge.”

Arnason explains that if the gear is functioning as it should, it will show wear on the lowest of the steel bars and a little on the second. “If they tell us that they are getting wear on the top bar then this is not right and we have to make some adjustment,” says Arnason.

Arnason points to graphics in the company literature that indicates the Flow Gear is lighter than the rock hopper gear when out of the water, and heavier in the water. “But the Flow Gear, does much less damage to the seafloor,” says Arnason, showing an underwater video of the Flow Gear rolling smoothly over rocks that the rock hopper gear rolls along for a few yards before jumping them.

“With rock hoppers, the pieces are sometimes sideways, and that creates a lot of drag. So, we find with the Flow gear, not only do you get more spread, but better fuel efficiency.”

Arnason also points to evidence that the Flow Gear creates water flow patterns along the leading edge of the sweep, driving fish to the center. “So, the fish are pushed toward the center, and fewer escape,” he says. “Look,” says Arnason, pointing at a photo of two cod ends on deck, both full but one noticeably fuller than the other. “These tow nets were towed side by side in Alaska; one with a rock hopper sweep, the other with Flow Gear. You see how much fuller the one with Flow Gear is?”

According to Arnason, five boats are now using the Flow Gear, and he expects more will take it up as word gets around.