Fishermen hope for net gain New designs may turn indiscriminate trap into precision tool

BOSTON – Diamond mesh, square mesh, black tunnels, vertical bars – New England fishermen are hoping that science can help save their industry with new designs that could change the fishing net from an ordinary trap to a precision tool.

The traditional dragger nets scoop up anything in their paths. Young fish that are not being targeted are killed and fishermen must throw away other species because of strict federal limits.

That waste is called bycatch, a problem so serious a federal judge is rewriting fishing regulations this week to prevent it, along with overfishing. Fishermen worry those new rules could put them out of business.

But the emerging science of net design aims to take advantage of fish behavior to create nets that let protected or unwanted species escape.

For instance, an experimental net with a black tunnel in the middle changes a fish’s tendency to blithely swim along as a net closes around them. The black tunnel causes fish to panic and dart as the net surrounds them. Smaller, younger fish escape through the mesh before it traps them.

Scientists say new net design can offer a middle-ground solution to the bycatch problem. “It has potentially huge benefits,” said Mike Pol, a biologist with the Massachusetts Division of Marine Fisheries.

But the science is young, and the testing so far may not be sufficient to get regulators to require major gear changes for the entire fleet.

“I think it is very promising,” said Teri Frady, spokeswoman for the National Marine Fisheries Service, which regulates New England waters. But “I don’t know if we’ve come to a point where we can say, ‘This will do this.”‘

Concern about bycatch intensified in December after conservationists won a federal lawsuit accusing the government of not doing enough to prevent bycatch and overfishing. U.S. District Judge Gladys Kessler will impose new fishing restrictions by Friday.

Avoiding cod, the region’s most important fish, is a major focus of new nets, as is preserving the younger, smaller fish that are critical to any stock’s future.

Scientists at Manomet Conservation Science Center in Plymouth, led by Chris Glass, have tested several nets that aim to be more selective. The new designs draw on what scientists have learned about fish behavior. For example, roundfish such as cod rise as they tire, while flatfish such as flounder stay near the ocean floor.

One design tested combines diamond mesh and square mesh at the end of the net where fish collect. The more horizontally shaped flatfish can fit through the diamonds at the bottom, while the square mesh top half allows younger cod to escape. Yearlong tests on the net with four fishing trawlers show up to a 70 percent reduction in bycatch, Glass said.

“The cost is absolutely minimal and you get a major reduction,” he said.

Separately, Provincetown fisherman Luis Ribas is receiving state money to test a net he designed. Ribas’ net has a panel of square mesh at the top front that allows the rising roundfish to slip through as the net drags.

Gear changes aimed at preventing bycatch have already been shown to work and are required equipment.

A “raised footrope trawl” – which is required for fishermen who catch whiting – allows fishermen to raise the net on chains so it stays off the ocean floor and spares flounder and other flatfish that swim there.