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Voracious Invasive Crab Threatening Maine's Shellfish Industry
08/28/2013   Reported By: Patty B. Wight

The hungry critter's first dish was mussels. Then scallops. Now it's soft-shell clams. And some fear lobsters will be next. European green crabs are devouring a shellfish buffet along Maine's seashore, plundering populations in their wake. To get a snapshot of just how severe the problem is, clammers, scientists, and marine officials took a survey today along Maine's coast. Patty Wight joined them in Freeport.

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Voracious Invasive Crab Threatening Maine's Shellf Listen

Clint Goodenow

Clammer Chad Coffin says there is a force to be reckoned with in Maine's ocean: Green crabs, he says, are dominating hundreds - if not thousands - of square miles of the intertidal zone, a favored habitat of clams.

"The Maine shellfish industry is in deep trouble," Coffin says. "We think that we're only maybe two years away from really no commercial viability in the state on softshell clams, which has been, historically and traditionally, one of the most important and economically valuable resources on the coast of Maine."

Clams are the third most lucrative commercial fishery in Maine, and green crabs are their number one threat. Clammers, marine officials and scientists are banding together to devise a strategy to stop the voracious predator. But first they need to get a better understanding of exactly where green crabs are, and how many of them are out there.

The one day, state-wide survey is the first step in getting that picture. Clammer Clint Goodenow (right) is one of dozens of volunteers who set baited traps Tuesday. Just 24 hours later, he lifts one out of the mouth of the Harraseeket River - and finds a motherload. "Whoa - look at 'em all in this one," he says. "That is a green crab trap!" another volunteer says.

The trap, which is about the size of a lobster trap, is teeming with green crabs. Goodenow dumps them into a plastic bin so that Department of Marine Resources scientist Kohl Kanwit can count and measure them. When she looks at them all, she sees more than just hundreds of green crabs scuttling about: "I see a dim future for the shellfish industry if we can't figure out ways to try and control these predators," she says.

Brian BealGreen crabs are invasive, but they're not exactly new. They arrived in Maine about a century ago, probably in ships that crossed the Atlantic. They weren't much of a problem until the 1950s, when ocean temperatures temporarily rose and the green crab population exploded.

Rising ocean temperatures are why they're a problem again. But what's troubling this time around, says Dr. Brian Beal (left), a professor of marine ecology at the University of Maine at Machias, is that these temperatures are likely here to stay due to global warming.

"And, unfortunately, because this is an invasive species, there's no predator that can keep the population in check," Beal says. "So we have to kind of depend on the weather and cold conditions in the wintertime, to really knock back green crab populations."

With little help likely to come from Mother Nature, the Department of Marine Resources is taking matters into its own hands. Commissioner Pat Keliher says multiple strategies are needed to protect clams and reduce the green crab population: things like installing fencing, setting traps - even turning green crabs into a commodity, like fish meal or lobster bait.

"You know, the efforts from just the clamming industry alone will not be enough," Keliher says. "It's going to need some sort of business entity that's going to want to come in and try to remove at a very high rate along the coast."

Keliher says it's not only shellfish that need protection, but critical seashore habitat. That's because green crabs are also decimating eel grass, which is a protective habitat for a number of other species. Clammer Chad Coffin says he's watching the change before his eyes.

"This is the first year in my life, in over 30-some odd years on the water, where you can actually motor up to some of these mussel bars in Casco Bay, because there's isn't any eel grass to foul the propeller," he says. "It's all gone."

Coffin says the information they gather from the survey will be used to figure out how to keep the green crab in check, and, hopefully, restore the clam population.

Photos:  Patty Wight

Photo of green crab: courtesy Maine Department of Marine Resources


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