President Trump signed a proclamation Friday that opened the Atlantic Ocean’s only fully protected marine sanctuary to commercial fishing, dismissing arguments that crab traps, fishing nets and lines dangling hooks can harm fish and whales.

Fishing can resume at the Northeast Canyons and Seamounts Marine National Monument off the coast of New England, Trump said. The Obama administration closed off nearly 5,000 square miles of ocean in September 2016 to save whales and allow marine life to recover from overfishing. The controversial decision was praised by conservationists and challenged by commercial fishermen from the start.

A coalition of fishing groups sought unsuccessfully to overturn the designation, made under the 1906 Antiquities Act, in federal court. They lost in both federal district court and in the D.C. Circuit Court of Appeals, and said they might seek to push the case to the Supreme Court.

“We’re opening it up today,” Trump declared during a roundtable discussion with commercial fishermen and Maine’s former Republican governor, Paul LePage. “We’re undoing his executive order. What was his reason? He didn’t have a reason, in my opinion."

Trump praised LePage for supporting the seafood industry and condemned Gov. Janet Mills, a Democrat who took office last year, for slowly reopening Maine’s economy as a safety measure during the coronavirus pandemic. He said Mills, who was not invited to the event, is “like a dictator.”

Mills said Trump’s talk was more of the fiery rhetoric “he uses to try to divide us” and to stoke fear. “What Maine people heard today was largely devoid of fact and absent of reality,” the governor said. “What Maine people saw today was a rambling, confusing, thinly-veiled political rally.

“I have spent the better part of my career listening to loud men talk tough to disguise their weakness. That’s what I heard today.”

The session in Bangor was attended by crabbers and lobster catchers, part of a $1 billion industry in Maine, who took turns praising the president. Some complained that they couldn’t sell to Britain because of unfair tariffs, which Trump said could be easily fixed by raising taxes on British goods.

And they repeatedly slammed the Obama administration for closing off the conservation area to fishing. In fact, the Obama administration had considered widening protections in the area beyond 5,000 miles but scaled it back after the state’s fishing industry expressed concern, conservationists said.

Maggie Raymond, executive director of Associated Fisheries of Maine, praised Trump at the event for directing a regional fisheries management council to determine what sort of fishing can take place in the once-protected area. “You’re bringing that process back,” she said.

“You’re so lucky I’m president,” Trump replied. “I don’t even know you, and you’re so lucky.”

Trump’s order was lauded by Saving Seafood, a fishing industry group, which thanked him “for restoring sustainable fishing activities in Northeast Canyons and Seamounts Marine National Monument.” Commercial fishermen can now fish in waters they had operated in for decades before the monument’s creation in December 2016, in areas that “President Obama and others called pristine even before commercial fishermen were banned.”

But there is no evidence that the creation of the conservation area has hurt commercial fishing in New England. In the period between the designation and the arrival of the coronavirus in the United States, landings and revenue for the industry did not decline, according to federal data. When Trump officials prepared a report on unwinding the monument designation, according to documents obtained under the Freedom of Information Act, they omitted data showing commercial operators “generated 5% or less of their annual landings from within the monument.”

No one has come forward with any data showing injury,” said Brad Sewell, senior director of oceans for the Natural Resources Defense Council, adding that the industry is now suffering during the pandemic “as are other people,” but the administration’s move will not bolster their income. “There will be zero jobs gained, zero landings increased. It’s a political stunt.”

Conservation groups said the return of fishing will hurt marine life.

“Today’s proclamation is another nail in the coffin for both productive fisheries and healthy oceans in New England," Gib Brogan, a fisheries analyst at Oceana, said in a statement. “By allowing all fishing back in the Northeast Canyons and Seamounts and removing the phaseout of the lobster and red crab fisheries, the hundreds of marine mammals that swim in the monument will be at increased risk of entanglement, including the endangered North Atlantic right whale. And deep-sea coral and sponge gardens that are thousands of years old will lose protection from damaging fishing gear.”

In an earlier interview, Brogan described Northeast Canyons as “a special place, with canyons indented into the continental shelf that creates oceanographic conditions that are full of life.”

“It’s a lot of species of whales — blue whales, sperm whales, right whales,” he said. Along with the danger of becoming entangled in ropes and nets, smaller whales have been known to grab baited hooks trailing long lines and sometimes die of injuries.

National Parks Conservation Association President and chief executive Theresa Pierno called the area “a living laboratory” where cod, tuna, sea turtles, sharks, seabirds and endangered marine mammals like North Atlantic right whales flourish.

GreenLatinos, a conservation group, called the proclamation “irresponsible and environmentally egregious” in a statement Friday. “Trump has continued to show disregard for the protection of our environment,” said Jessica Loya, the group’s director of policy and programs. “Trump’s proclamation is yet again an open invitation for corporate profit-driven entities to take advantage of the American people and critically endangering our environment, and endangering marine life.”

Even if a new president restores protections next year, the back and forth will establish a dangerous precedent, Sewell said.

“There hasn’t been this kind of yo-yo before, and it’s disturbing and not in the interest of all Americans to have protected lands, and then have protections lifted, and then have protections put back in place,” he said.

Northeast Canyons sits 130 miles off Cape Cod, the nation’s first fully protected area in the Atlantic. There are other offshore monuments and sanctuaries — Papahanaumokuakea Marine National Monument off Hawaii, Monterey Bay National Marine Sanctuary off California and the Thunder Bay Marine Sanctuary off Michigan — but Northeast Canyons is more accessible to boaters off the New England coast.

Many species of deep-sea coral, sharks, sea turtles, seabirds and deep-diving marine mammals live along areas along the continental shelf. Towering underwater peaks called seamounts rise 7,700 feet, taller than the Rocky and Appalachian mountains.

The United States controls more of the ocean than any other nation: its exclusive economic zone accounts for 55 percent of total U.S. acreage of federal lands and waters. Only 2.3 percent of the sea is strongly protected worldwide.

Soon after Trump took office, he ordered the Commerce Department to review marine sanctuaries that were established or altered within the past 10 years. Then-Interior Department Secretary Ryan Zinke held a listening session with fisherman and recommended allowing commercial fishing to continue at Northeast Canyons.