In invasive green crabs, Maine faces one of its older foes.

Denis Nault, Shellfish Management Program Supervisor for the Maine Department of Marine Resources, said the crabs have been eating mussels, shearing crab grass and digging up clams for 80 years in Maine.

“There are written reports of green crabs invading Jonesport in the 1930s,” Nault said. “There was another population boom in the late ‘50s, early ‘60s, but nothing like what we saw last year.”

That sudden boom in population has put green crabs on the radar, and in some cases, the menu.

But the species’ low value as a food would keep it hidden. Green crab isn't considered a delicacy, like its blue cousins to the south, meaning little consideration was given to the species.

“We weren't looking at green crabs,” Nault said. “It's always been a 'junk' species, and suddenly we have this population explosion and it's 'Holy smokes, we didn't see it coming’.”

Because there was no market for the green crab, no counts and few studies were commissioned until recently.

“In a way, this year will serve as our baseline,” Nault said.

What has protected the crab might be what levels its population: A market for the invasive species is growing.

Canadian Ron House has recently made his intentions known that he would like to begin harvesting live and shucked green crabs to sell as food. One of the emerging destinations for the meat will be in Asian markets, Nault said.

Another market aims for the kitchen floor, rather than the table: North Carolina-based Bay City Crab ran an advertisement in the July 23 edition of the Boothbay Register asking for green crabs, to take the place of more expensive and rarer blue crabs in the making of cat food.

But, it isn't just commercial operations that are looking at green crabs.

Municipalities have started trapping green crabs, and the license cost was dropped from $38 a year ago to $10 to try and boost numbers.

Just as soon as populations rise, they can shrink, Nault said. Green crab populations are extremely prone to ocean temperatures, and with the gradual warming of the ocean the populations have spiked. However, the long, cold winter of 2013-14 seems to have tempered that growth, at least according to anecdotes, Nault said.

“Several municipalities have reported a drop-off,” he said. “Part of that is likely due to a cold winter and a cool, wet spring.”

Why worry about green crabs? For one, the invasive species often goes unchecked when it eats through native species, Nault said.

“They wreak havoc on mussels, especially,” he said. “(Green crabs) will also eat through the small (soft shell clams); they're pretty easy to break through.

“When times get tough, they have been known to eat quahogs and they've even been seen eating moon snails.”

But, it isn't just the fauna that's in danger from the small, green invaders: Nault said eel grass gets trimmed down to size and Spartina, which grows in marshes, is especially vulnerable to green crabs.