PORTLAND – A federal analysis that predicts a loss of up to 500 jobs in Maine under proposed groundfishing rules underestimates the full economic impact, the general manager of the Portland Fish Exchange says.

Hank Soule said the sweeping new regulations, known as Amendment 13, could force many fishermen to relocate from Maine to Massachusetts.

The regulations, designed to help rebuild fish stocks, could reduce the number of days a boat can fish from 70 to 40 per year. Maine fishermen would be at a disadvantage because they have farther to travel to reach prime fishing grounds on Georges Bank.

By moving to Massachusetts, they could cut down on their “steaming time” and save 10 to 15 travel days a year, using them for fishing instead.

“A good number of fishermen are saying ‘If this goes through, I’m leaving,'” Soule said.

The Portland Fish Exchange landed 22 million pounds of groundfish last year, about half of which came from 25 larger boats that work farther offshore. Soule said he expects most of those boats to move their operations to Massachusetts.

“I am going very quickly, I believe, from 22 million pounds here to 10 million pounds,” Soule said. “That’s a pretty significant reduction, and the exchange hasn’t operated on that volume of landings since it opened.”

The New England Fishery Management Council will hold public hearings next month on four options for satisfying Amendment 13. In addition to the cuts in fishing days, options include fishing area closures and strict quotas on cod, haddock and other groundfish. The council will vote on a final plan in November, and the regulations that are ultimately adopted will go into effect next May.

Portland Mayor James Cloutier says the loss of the Portland Fish Exchange would be disastrous for the city’s economy and image.

A new fisheries policy advisory committee composed of people working in or with the fishing industry is developing an “anecdotal analysis” to outline the problem and detail how Portland has already been affected by tighter fishing restrictions, he said.

Cloutier said that analysis should be completed sometime next week, when the committee will draft a resolution to take to the City Council. The committee also will call on the state to perform its own economic analysis of the effects of the regulations, he said.

The city already has lost about half of its fishing crews and boats because of fishing regulations, Cloutier said. More restrictions would be “unwise and unfair,” he said, and do “some fairly large damage to the Portland economy.”

The loss of fishing boats in a port has a ripple effect onshore because it affects fishing-related businesses that supply food, fuel, repair work and other commodities that fishermen need.

More defections from Maine could have a devastating effect on the Portland Fish Exchange, which has already lost 20 percent of its landings to Massachusetts, according to Tom Valleau, president of the organization’s board of directors.