A federal appeals court has sided with commercial fishermen who say proposed restrictions aimed at saving a vanishing species of whale could put them out of business.

The fishermen harvest lobsters and crabs off New England and oppose tough new restrictions on the way they fish that are intended to protect the North Atlantic right whale. The whale numbers only about 340 in the world and it’s vulnerable to lethal entanglement in fishing gear.

The fishermen and the state of Maine appealed their case to the U.S. Court of Appeals for the District of Columbia Circuit after losing in a lower court. The appeals court said Friday it disagreed with the lower court’s ruling.

The appeals court ruling could mean that the federal government must take another stab at crafting new rules to protect the whales. The restrictions would limit where lobster fishers can fish and what kind of gear they can use to try to prevent the whales from becoming entangled in fishing ropes.

The changes would represent a potential worst-case scenario for the lobster fishing industry, wrote Douglas H. Ginsburg, the senior judge of the appeals court, in Friday’s ruling.

“The result may be great physical and human capital destroyed, and thousands of jobs lost, with all the degradation that attends such dislocations,” Ginsburg wrote.

The fishers sued the National Marine Fisheries Service, an arm of the federal government. The service declined to comment on the lawsuit.