PORTLAND – Maine lobster industry leaders support a proposed seasonal ban on fishing boats that catch herring, the primary source of bait for the state’s thousands of lobstermen, in coastal waters.

Fishery regulators are recommending that the federal government impose a seasonal ban on boats known as midwater herring trawlers because they fear the herring population may be at risk.

Besides the lobster industry, the measure is supported by whale-watching companies, recreational fishermen, tuna fishermen, environmentalists and groundfishermen who fish near shore.

Herring is one of the most important species in the Gulf of Maine because it provides a critical link in the food chain. Herring feed on tiny zooplankton and are consumed by top marine predators, such as whales, seals, harbor porpoises, cod, tuna, bluefish and striped bass.

Herring is especially important as bait for lobstermen, who need a steady and affordable supply throughout the year, said Patrice McCarron, executive director of the Maine Lobstermen’s Association.

“From a conservation and stewardship point of view, we need to make sure we don’t hammer that resource because it is going to affect everything,” she said.

The ban as proposed would extend 50 to 60 miles offshore from June 1 to Sept. 30, when trawlers take the bulk of the season’s catch.

The plan would allow trawlers to operate in offshore parts of the Gulf of Maine and on the Georges Bank fishing ground. It would allow fishermen to catch herring near shore in the summer, but only with purse seine nets, which encircle the fish when they come to the surface to feed.

The trawlers, in contrast, drag massive nets through the water and sometimes work in pairs, dragging an even bigger net between them.

The proposal was approved by the New England Fishery Management council last week and is expected to be approved by the National Marine Fisheries Service.

For herring fishermen, the ban would cost millions of dollars to convert to purse-seine fishing, said Mary Beth Tooley of the East Coast Pelagic Association, which represents herring fishermen in Maine, Massachusetts, Rhode Island and New Jersey.

Such a conversion would cost $500,000 per boat, she said.

Roger Fleming, a senior attorney with the Conservation Trust, said the council vote is good news for many fishermen, environmentalists and eco-tourism businesses, such as whale-watching companies. He said whales won’t swim near the coast if there is not enough food for them to eat.

Scientists say there are plenty of herring in the open ocean.

But in recent years, the boats have reached their catch limits in the coastal zone earlier in the season, causing herring supplies to tighten and prices to rise.

But the herring fleet has not been reaching catch limits in other sections of the Gulf of Maine or on Georges Bank.