PORTLAND – The northern shrimp season got under way Dec. 1 in the Gulf of Maine and fishermen say the catches are good and prices are up to one-third higher than last year.

But those gains, they say, have been offset by the high cost of diesel fuel, which makes shrimp harvesting an iffy venture in offshore waters.

“A lot of fishermen are shaking their heads and they’re like, ‘Gee, this isn’t making any sense,”‘ said Bert Jongerden, manager of the Portland Fish Exchange. “It’s hard to justify casting the lines off.”

Jongerden said about 10 boats have been landing shrimp at the exchange since the season started. In peak years, back in the mid-1990s, the fishery attracted up to 300 vessels from the midcoast to the New Hampshire border.

Jongerden said many more boats likely will join in later this winter when shallow waters become colder and the shrimp migrate closer to shore.

“I think they are all kind of sitting on the fence waiting for the shrimp to get a little closer,” he said.

A state law intended to protect lobsters and limit gear conflicts bars shrimp fishermen from dragging within three miles of shore until after Jan. 1.

Rob Tetrault, one of many groundfishermen who harvest shrimp to supplement their incomes, said he leaves the dock extra early so he can run his 54-foot boat slowly and save fuel on the 15-mile run to the fishing grounds.

But he still burns about 150 gallons a day, at $3 per gallon. On Tuesday, when Tetrault and his two crew members returned to the exchange with 3,000 pounds of shrimp, it would take nearly one-third of the catch to pay for the day’s fuel.

“We don’t start making money ’til the afternoon, ’til the last two tows of the day,” he said.