Offshore herring stocks, not fully exploited in recent years, will be the target of a new freezer vessel based in Portland.

Supporters say the venture will reduce pressure on overexploited inshore stocks, while critics worry the freezer boat will cause economic damage to onshore processing plants in other New England states and mean less food for larger fish species and less bait for the lobster industry.

American Freedom, a 380-foot freezer vessel that will process both mackerel and herring at sea, left Portland in early January for its shakedown trip to Cape Cod and Long Island.

Owned by Jim Odlin, president of Atlantic Pelagic Seafood, LLC, and silent partners, the vessel will take fish from a group of three to five fishing vessels based in New Bedford, Rhode Island and Maine, freeze it on board and export most of the product — primarily to Africa and Eastern Europe — for food.

Smaller fish that can’t be sold for food will be brought ashore in New England for use as lobster bait, said Odlin.

Two of the southern catcher vessels are owned by Odlin’s Atlantic Trawlers. One of his Portland boats is also expected to work with the American Freedom. One of the vessels slated as a catcher boat for the first part of the venture is independently owned. Reportedly, subsequent trips will make use of other independents.

A New England Fishery Management Council (NEFMC) analyst, Lori Steele, said fishermen routinely reach inshore quota limits for herring, but have never reached the quota for Georges Bank or further offshore. Oldin, a member of the NEFMC, has the council’s support.

The Odlin plan, representing an investment of $24 million so far, will make herring fishing economically feasible for fishermen, she said, because they can offload the highly perishable, fatty fish right after they are caught.

Most New England fishermen do not have boats equipped with cold seawater tanks for preserving the delicate pelagics. This system saves on fuel costs for fishermen since they don’t have to return to port to offload each catch.

“Vessels won’t have to bring the fish home,” Steele said. “They can land the fish at sea. It’s a new kind of opportunity.”

However, ten years ago North Yarmouth fishermen proposed fishing for herring with a freezer-trawler the size of the Odlin boat. Opposition to the plan forced its abandonment and prompted a federal ban on fishing boats larger than 165 feet from entering the fishery until a new management plan was approved.

Now there is a new management plan, and American Freedom, a former Alaskan salmon processor, doesn’t catch fish.

Environmentalists have expressed concern that larger species, including whales and commercial stocks such as groundfish, won’t have enough to eat if herring stocks are depleted.

Attorney Roger Fleming with the Conservation Law Foundation said regulators need to set aside forage fish first of the ecosystem and less for fishermen. “My concern is that I do not think we have accurately accounted for the role of herring in the ecosystem yet.”

Odlin has guaranteed he will pay to keep a federal fisheries observer aboard the freezer vessel, even though National Marine Fisheries Service’s budget for observers has been cut.

Maine’s lobstermen worry they won’t be able to find enough herring to use for bait in the state’s most valuable fishery.

“We are very concerned about it,” said Pat White, York lobstermen and former head of the Maine Lobstermen’s Association. “We need more information to know the status of the resource.”

The amount of herring available for bait is expected to diminish because of the departure of New Hampshire-based Shafmaster from the herring fishery, said White. The National Marine Fisheries Service has cut the inshore herring quota for this season, reducing amount of herring available to be caught by inshore fishermen.

“We’re willing to take him at his word, to see if he brings in fish the lobster industry can use,” said White. “I opposed it anyway because I think the fish should be processed onshore.”

After the U.S. banned foreign freezer trawlers from the fishery within 200 miles of its coast, in the 1970s, herring stocks took 20 years to rebound. Some critics say introducing vessels like those from the banned foreign fleet is self-defeating, especially since New England businesses have been encouraged to build shoreside plants.

Vito Calomo, executive director of the Massachusetts Fisheries Recovery Commission, opposes allowing the freezer vessel to compete with existing shoreside facilities. “We are allowing what we got rid of when we phased out the foreign nationals,” he said.

Odlin has said he believes his operation meets the intent of regulators when they banned the foreign fleet, saying, “It’s all about Americanizing the fishery.”

White said he doesn’t want to say the sky is falling because “we’ve said that so many times. Of course, we’ve usually been right.”