PORTLAND – The Maine lobster industry has long been held up as a well-run fishery. Now it’s seeking a seal of approval to prove it.

Efforts are under way to have the state’s signature seafood certified as sustainable by an international organization that evaluates fishing practices worldwide. With consumers demanding more “green” food products, the lobster industry stands to lose out if it doesn’t get certified, supporters say.

“It’ll open up a lot of markets for us,” said John Hathaway, owner of Shucks Maine Lobster processing company in Richmond. “If we don’t do it, we’ll probably lose markets.”

The London-based Marine Stewardship Council has been in the business of encouraging responsible fishing practices since 1997. Fisheries that are certified as “sustainable” can use the council’s blue ecolabel, a seal that assures consumers the seafood was not overfished or harvested in a way that harms the ocean.

The MSC has certified 26 separate fisheries around the world, and nearly 1,200 seafood products carry the group’s label.

A growing number of retailers and restaurants are jumping on the bandwagon.

Wal-Mart has pledged that, in the next few years, all wild-caught seafood it sells in its North American stores will be certified as sustainable. Other U.S. chains, including Whole Foods, Target and Costco, have committed to the program in varying degrees.

It’s hard to ignore heavy hitters like those, said Linda Bean, owner of Port Clyde Lobster.

“We’re convinced that the demand for Maine lobster will be greatly affected if we don’t do this,” she said. “We’ll be out of the loop.”

Maine is the nation’s lobster breadbasket, accounting for about 80 percent of the U.S. catch. American lobster was the single most valuable U.S. fishery in 2006, worth $395 million, according to the latest statistics from the National Oceanic and Atmospheric Administration.

Gov. John Baldacci has appointed a task force to pursue the MSC certification for lobsters caught in Maine. Its members are Department of Marine Resources Commissioner George Lapointe, Hathaway and Bean, granddaughter of L.L. Bean, who founded the outdoor apparel company that bears his name.

Hathaway and Bean plan soon to start raising funds privately to pay for a third-party company to evaluate the harvesting practices, regulatory regime and science of the lobster fishery. The assessment will be submitted to the MSC for approval. The process probably will take more than a year.

If approved, Maine lobster would join other certified fisheries that run the gamut from cod and haddock to shrimp and salmon. The list ranges from large fisheries such as Alaskan salmon and Bering Sea pollock to the tiny Thames River herring and Burry Inlet cockle fisheries in the United Kingdom. Among lobster, the western Australia rock lobster and Mexican Baja California spiny lobster fisheries have been certified.