For the first time in years, big schools of menhaden are migrating into Narragansett Bay and attracting out-of-state fishermen who use airplanes to find the schools of small bait fish and auxiliary boats to deploy vast nets to sweep them up.

The upsurge caught state fishing regulators by surprise and prompted the state Department of Environmental Management two weeks ago to change course from minimally managing the fishery to enacting an emergency regulation limiting each boat to 75,000 pounds of fish daily.

No one can explain with certainty the sudden increase in menhaden. But it further complicates a struggle between recreational and commercial fishermen over who will have access to what had been a badly depleted fish population.

This year, the long-simmering feud erupted at the State House over a bill that would have banned commercial fishermen from netting menhaden in Narragansett Bay.

The bill never got out of committee. It was never heard in a public hearing. But it spawned letter-writing and e-mail campaigns, prompted bitter arguments and broke up at least one friendship.

Save the Bay, the state’s largest environmental group, had endorsed the bill and then raised the ante by hosting a New Jersey professor named H. Bruce Franklin, whose book The Most Important Fish in the Sea raises alarms about declining menhaden.

The Rhode Island Saltwater Anglers Association sponsored a petition supporting the bill signed by 11,697 people.

Stephen J. Medeiros, president of the association, said his membership voted 700 to 30 to push for the fishing ban because, “when the bait boat comes in and scoops up all the fish, it leaves nothing behind.”

Over and over, critics said they were upset about the efficient methods of the purse seine fishermen, who track schools of menhaden with airplanes, and then use small boats to circle schools with large nets. They draw the nets closed and then vacuum up the trapped fish, appearing to wipe out entire schools.

The state Department of Environmental Management opposed the bill. Its biologists said there was no science to support it. While menhaden were down, they were not overfished. Only one commercial vessel, operated by Ark Bait in Fall River, fished for them commercially in the Bay.

But the most vocal opposition came from about 200 lobstermen who depend on menhaden as an inexpensive bait for their traps. They argued the menhaden were not threatened. But their livelihoods would be if they lost access to the inexpensive bait.

In May, longtime lobsterman Russ Wallis, a low-key presence at many fisheries meetings, angrily dropped his membership in Save the Bay.

“Having been a longtime supporter of Save the Bay, this whole fiasco has really opened my eyes as to how Save the Bay operates today as opposed to years ago,” Wallis said in an e-mail to Save the Bay Baykeeper John Torgan, with whom he had shared many lunches over the years. Wallis signed the e-mail: “Your ex-friend and ex-member.”

The menhaden battle came at a tough time for Rhode Island lobstermen. Faced with declining catches, last year the state essentially privatized the local lobster industry, allowing only about 200 fishermen access to lobsters. About 150 fishermen who were locked out formed a new fishermen’s group and sued the state.

“It’s been quite a year for fisheries management,” said Mark Gibson, deputy chief of marine fisheries at the DEM.

In the 1970s, Gibson said, catches of 30 million to 40 million pounds of menhaden in Narragansett Bay were commonplace. But the numbers dropped to such low levels in recent years that the DEM didn’t attempt to quantify them, he said. One boat, Ark Bait’s Sea Huntress, would fish the Bay as long as it found menhaden. When the fish were gone, the boat would move on to New Jersey waters and truck its catches back to Fall River.

Over the years, the state worked out regulations to limit commercial menhaden catches, and, it seems, to keep the commercial boats away from the recreational fishermen. Commercial fishing was kept out of Greenwich Bay and portions of the Providence River, for instance. Commercial fishermen were also banned from fishing on weekends and holidays.

“It was sort of a gerrymandered affair based on negotiations among warring parties,” said Gibson. “But it apparently was no longer acceptable to the recreational fishermen. They went to the legislature, knowing the DEM wouldn’t support them.”

Medeiros, president of the anglers association, said recreational fishermen have sought further restrictions for years.

The fishermen approached the DEM last year, but it didn’t respond, he said. The fisheries management council wouldn’t support them.

“It’s a passionate issue, for both sides,” Medeiros said. He said he warned his membership that going to the legislature would trigger a tough battle. But they voted so overwhelmingly to go ahead, he felt compelled to act, he said.

Rep. Raymond E. Gallison Jr., D-Bristol, says he agreed to sponsor the bill because he has seen the purse seine boats at work and didn’t like what he saw.

“You hear the spotter plane at 6 a.m. and then you look out and see the boat out there,” Gallison said. “There’s a school of fish, and then the school is gone. To me that’s a problem. They take too many fish at once.”

Rep. Jan P. Malik, D-Warren, representing a neighboring district, led the opposition. The legislature has been criticized for going too far with the lead-paint law and the fire codes, he said. This time, he said, it should leave a difficult issue to the experts to handle.

Malik said he’s happy the recreational fishermen brought up the issue. And he says the Assembly should revisit it next year. “If we are going to react, let’s get some facts. Let’s not be cowboys here.”

IN MARCH, the DEM’s Gibson put his objections to the proposed commercial fishing ban in writing to DEM Director W. Michael Sullivan:

• Unlike herring or salmon, which return to where they spawn, there is no local stock of menhaden that needs special protection. There is no evidence that they return to specific estuaries.

• A regional regulatory body, the Atlantic States Marine Fisheries Commission, has not found menhaden to be overfished. The numbers are far lower than in the 1970s, but that decline was attributed to the reduction industry — massive boats that caught menhaden to be reduced for its protein. Those fisheries have been banned by Rhode Island and most other states on the East Coast. Since then, menhaden populations have stabilized.

• Predation by other fish has now probably supplanted fishing as the prime cause of mortality in menhaden.

• There is no evidence that the adult menhaden sought by commercial fishermen play a significant role in biologically filtering the Bay, nor are they a prime source of food for stripers, which prefer very young menhaden.

Gerald Souza, one of the owners of the Ark Bait business, said Gibson’s report was factual. “There are a hell of a lot of fish out here. We kept telling them that,” Souza said on a cell phone from his boat as he fished.

For 30 years, he and his partners have been keeping their business going and helping local lobstermen, and now the recreational fishermen want to put them out of business, Souza said. Even the new emergency caps on daily catches are costing them a lot of money, Souza said, because the fish are so abundant this year, he could catch more than the quotas.

“We love the water. We all gave up jobs with security and insurance to do this, and now they want to take it away from us,” said Souza.

Wallis, the lobsterman, said one reason commercial fishermen are upset is because too many people paid attention to Franklin’s book. It was written by a recreational fisherman objecting to reduction fishing in Chesapeake Bay, which Wallis said is not analogous to conditions in Narragansett Bay.

People don’t appreciate that lobstermen used to get plenty of cheap bait from the fish frames (body parts) that remained after groundfish were filleted. But with the groundfishing collapsed, lobstermen now pay far more for bait. Last year alone, Wallis spent $23,000 on bait.

AT THE STATE HOUSE, a compromise was almost — but not quite — negotiated. It would have protected more of the Bay, but not the entire Bay, from commercial fishing.

Now, everyone agrees the issue will be revisited by the legislature next year. Fishery experts at URI plan to host a conference in the winter to examine data on menhaden, and the DEM will probably do the same this fall in a public hearing.

In the meantime, the DEM has stepped up its management of the now-revived menhaden population. It set a quota for each boat and put personnel on the purse seine boats and in the spotter planes to collect data.

“As long as it was one boat selling pogies to lobstermen, we weren’t too concerned,” said Gibson. “But once we realized that a significant number came in this year, and it became a politically charged issue, we had to show we could manage this in-house. There is no room any more for managing them by the seat of the pants.”

Save the Bay’s Torgan said he was on the Bay last week when an out-of-state boat arrived and began sweeping up schools of menhaden. It had far more capacity than the Ark Bait boat.

“We saw it. There were lots of dead fish,” Torgan said. “It was outrageous. They worked right up to the hurricane barrier [in Providence].”

Last week the upper Bay was quiet. But Gibson said at least two boats were netting fish every day in the Sakonnet River, Mount Hope Bay or off Quonset Point.