PORTSMOUTH, N.H. — A New Hampshire group wants to be the first to bring offshore fish farming to the waters off New England by raising salmon and trout in open-ocean pens miles from land, but critics fear the plan could harm the environment.

The vast majority of U.S. aquaculture, the practice of raising and harvesting fish in controlled settings, takes place in coastal waters or on land, in tanks and ponds. But New Hampshire-based Blue Water Fisheries wants to place 40 submersible fish pens in water about 7.5 miles off Newburyport, Massachusetts, on two sites that total nearly a square mile, according to federal documents reviewed by The Associated Press.

The farm would grow millions of pounds of Atlantic salmon and steelhead trout, two popular seafood species, documents state. The proposal needs a battery of approvals, and would be the first of its kind off the East Coast.

Hawaii was the first U.S. state to allow operation of commercial open ocean aquaculture. Supporters of the farms tout them as a new method of sustainable fish farming, but environmental groups have voiced concerns about pollution and the possibility of projects releasing non-native species. Other offshore fish farming projects have been proposed for the waters off California and Florida.

The New England company hasn’t said much about its plans. Scott Flood, who is listed as a representative for Blue Water Fisheries on documents, declined to comment on the project. Other representatives for the company did not return phone calls seeking comment.

The National Oceanic and Atmospheric Administration is working with Blue Water Fisheries and other federal agencies on the regulatory and approvals process, said Allison Ferreira, a spokesperson for the agency. The company needs authorizations from NOAA and the U.S. Environmental Protection Agency, among other approvals.

A key step in the approvals process for Blue Water Fisheries is the preparation of an environmental impact statement, Ferreria said. There is not yet a timeline for that process, she said.

The aquaculture project would include pens submerged about 49 feet below the surface in depths of about 262 feet, federal documents state. The project would yield “up to 25.6 million pounds of a combination of steelhead trout and Atlantic salmon annually,” the documents state. The company’s year-round operations would take place out of Portsmouth, New Hampshire.

The project also includes a proposal to aquaculture lumpfish, a species of fish that can be used to control parasites.

Aquaculture of Atlantic salmon in ocean pens already takes place in New England, as fish farming giant Cooke Aquaculture cultures the fish off Maine. However, those operations are located in coastal areas.

Any project involving the offshore culture of Atlantic salmon is likely to get the attention of conservation groups, as the salmon are listed under the Endangered Species Act in the U.S. Conservation groups have long made the case that farming salmon in the marine environment is bad for wild salmon, in part because the farmed fish can escape and jeopardize wild salmon by hybridizing with them and competing with them for food. They’ve also sounded alarms about the spread of parasites and the transfer of diseases.

Conservation groups have also argued the fish farms are bad for the environment because of pollution in the form of the antibiotics and pesticides often used on the farms.

Fish farming also has its supporters, who say the aquaculture of popular seafood species helps to take fishing pressure off wild fish stocks.

The New Hampshire group’s project raises potential alarms about possible fish escapes, said John Burrows, executive director for U.S. operations with the Atlantic Salmon Federation, a conservation organization. Using net pens far from the shoreside operations “significantly raises the likelihood of storm damage or predators causing escapes that may go undetected for several days,” Burrows said.

Don’t Cage Our Oceans, a national group that opposes offshore fish farming, is also monitoring the project, said Andrianna Natsoulas, the coalition’s campaign director.

“This is highly problematic, especially at the massive scale of this proposed operation once fully built-out,” Burrows said.