CONCORD, N.H. — New Hampshire has joined a federal lawsuit seeking to block fishing regulations it believes would have a devastating effect on families and small businesses throughout New England.

A court has approved the state’s request to become an intervener in the lawsuit Massachusetts filed against federal regulators in May, Gov. Maggie Hassan and Attorney General Joseph Foster said Monday.

The rules, which took effect May 1, included major cuts in catch limits for bottom-dwelling ground fish.

The most significant cut is a 78 percent year-to-year reduction in the catch of Gulf of Maine cod, but fishermen have also absorbed huge reductions in key flounder and haddock species.

“The onerous restrictions and reduced catch limits put forth by the federal government could have a dire effect on the economic viability of New Hampshire’s fishermen, placing one of our state’s oldest and most treasured industries at grave risk and undermining an important sector of our economy,” Hassan said.

In the months before the rules took effect, regulators took various steps to try to ease the blow, including increasing the quota on healthier species. But the Northeast’s top regulator, John Bullard, has repeatedly said the sharp cuts, though painful, are needed to help fish stocks rebound.

In court documents, New Hampshire argued the rules could have a disproportionate impact on the state’s fisheries because they employ smaller vessels that tend to fish closer to shore. And New Hampshire might not agree on how to argue their case or appropriate remedies, Foster said.

“What would be good for Massachusetts would not necessarily be good for New Hampshire,” he wrote.

New Hampshire fishermen landed 7.5 million pounds of fish last year worth $5.6 million. Of that total, the ground fish at issue in the lawsuit were worth $3.9 million.

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