PORTLAND – Regulators on Monday approved a 152-day northern shrimp season, a day longer than last year’s, but expressed concern about a possible decline in shrimp stocks that could curtail fishing in 2009.

The Atlantic States Marine Fisheries Commission’s shrimp committee announced that the seven-day-a-week season will run from Dec. 1 through April 30.

“Our efforts to reduce fishing mortality in the early 2000s continue to provide an above-average abundance of shrimp for the fishery,” said Ritchie White of New Hampshire, the panel’s outgoing chairman. “By approving another five-month fishing season, we are able to maintain improved harvesting and marketing opportunities.”

The committee made a conditional commitment to set a 2008-09 season that runs from December through April, but noted that the number of fishing days within that period may have to be reduced based on next year’s stock assessment.

It appears that fewer shrimp were hatched in 2005 and 2006, the committee noted, which means that the 2004 class may be the only one capable of supporting a fishery in 2009. It takes roughly 31/2 years for shrimp to reach maturity.

“There’s always been weak year classes that show up. It’s just most concerning when there are two such in a row,” said Braddock Spear, the commission’s shrimp management plan coordinator. “We still have yet to see the 2007 year class. So if that was a weak one also, then there’d be some serious concern.”

Northern shrimp provide a small but valuable fishery to fishermen across New England, especially in Maine, where about 150 boats took part in last year’s season. An additional 20 boats from New Hampshire and Massachusetts combined also participate.

After several boom shrimp fishing years in the 1990s, a decline in Gulf of Maine shrimp stocks forced the commission to shorten the season for shrimp fishermen. The season was just 25 days in 2002-03, 38 days in 2003-04 and 70 days in 2004-05 before it was doubled to 140 days in 2005-2006.

The fishery is jointly regulated by Massachusetts, New Hampshire and Maine.