BOSTON – Scientists say northern shrimp stocks are dangerously depleted, which leaves Rockport fisherman Bill Lee to wonder why he caught more than he could sell this year.

Earlier this month, Lee couldn’t unload a haul of shrimp because the dealers had all they needed. Instead of wasting it, he gave it away at the Gloucester machine shop that services his boat.

“He had a ton of it and it was spread out to everybody,” said Carol Rose, a bookkeeper at Rose’s Oil Service Inc. “It was great.”

Fishermen aren’t as enthusiastic about the glut. They say shrimp are plentiful, but there’s no one to buy it, as processors become increasingly unwilling to invest in a season that has shrunk to about two winter months.

This season, which ended March 12, the soft demand caused prices to plummet even as fishermen were squeezed by rising fuel costs. What was once a multimillion-dollar industry is barely hanging on, Lee said.

“If the same thing happens next year, I think it’s gone,” Lee said.

The northern shrimp is a cold-water animal that lives in waters from Massachusetts to Canada, with the bulk of the U.S. catch coming in Maine. The shrimp is hermaphroditic, maturing as a male before transforming to a female at about 31/2 years. Its five-year life cycle makes for volatile population swings, said Braddock Spear of the Atlantic States Marine Fisheries Commission, which manages the shrimp.

The fishery was shut down in 1978 after the stock collapsed, but it rebounded by the mid-1990s, when annual revenues ranged as high as $15 million. In 2002, the last year statistics were available, revenues were a paltry $1 million. Meanwhile, prices this season were 25 to 40 cents per pound, compared to $1.07 in 2002.

Scientific surveys showed a shrimp population limping so badly that an ASMFC advisory committee recommended closing the fishery this year. The survey showed virtually no juvenile shrimp born in the years 2000 and 2002. Managers ended up allowing just 45 days, compared to 105 days as recently as 1998.

It’s a mystery why the stock hasn’t rebounded, even as fishing days have been cut, Spear said. Warming water temperatures or other environmental conditions are possible explanations, but no one really knows, he said.

Bill Bayley of Bayley’s Lobster Pound in Scarborough, Maine, said he once hired help to process 300,000 pounds of shrimp a year for the wholesale market. Now, his existing staff handles a few thousand pounds for retail sales.

“Are you going to hire people that are going to work for five or six weeks?” he said. “It’s almost impossible.”