The European green crab has been on the East Coast of the United States for over a century, but the impact of the invasive species has for much of that time been relatively small and manageable.
That “low impact” is rapidly changing for the worse as warmer waters in the Gulf of Maine are causing more and more green crabs to survive over the winter and reproduce. With few natural predators to stop them, and an impressive ability to reproduce, the crabs are rapidly taking over in Maine.
The consequences are already being felt in the state’s softshell clam industry. Landings in 2017 were the lowest they’d been since 1930 at just 6.8 million pounds. The mussel harvest also hit a historic low last year.
If the population continues to rise and nothing is done, the softshell clam industry, and many other native species, could be decimated in the coming decades.
Industry and environmental leaders in the region aren’t going to let that happen without a fight, which was why the second ever “Green Crab Working Summit” took place on 6 and 7 June in Portland, Maine. The summit brought together ecologists, local fishermen, and chefs to share ideas and concepts for how to address the problem in a proactive way.
Summits have been convened in the past, but this was the first “working summit,” according to Marissa McMahan of Manomet, a nonprofit based in Massachusetts. She helped organize the event along with Gabriela Bradt, of New Hampshire Sea Grant, a partnership between the University of New Hampshire and the federal government mandated by Congress to foster sustainable development of the nation’s coastal resources.
“We wanted this summit to be interactive,” McMahan said.
Interactivity was on display at the summit as Jamie Bassett of Green Crab Nation – a volume supplier of green crabs – demonstrated how to extract roe from the small crustacean.
Bassett had a full tray of already-cooked crabs ready for anyone to try the technique to extract the roe and meat from the inside to get a sample of the creature’s flavor. Historically, the crabs haven’t been utilized as a food source on the U.S. East Coast.
“Think, put that on a little slice of cucumber, and you don’t need much,” he said as he held out an orange-red piece of meat. “This, on a sushi plate, it’s bite-size, very delicate.”
Three professional chefs were also on hand to play around with green crabs and create some interesting dishes for sampling, with an audience watching demonstrations on how to prepare a dish. The goal, said McMahan, is to brainstorm how to create a market for the invasive pest to both help manage population and create a new commodity for fishermen.
From a nutrition and taste standpoint, the small crabs have some good things going for them. Angela Myracle, assistant professor of human nutrition for the University of Maine, has been looking into the benefits of the crustacean, such as bio-active peptides that could have positive health effects, on both humans and animals.
“We’re looking at this from a food perspective,” she said. “If we get it into the food stream, I’m sure it will have a niche.”
Scientists were also on hand to discuss the findings of their various studies into green crabs and what sort of measures could be taken to help control them. Ted Grosholz, an ecologist with the University of California, Davis, gave a presentation on an extensive effort to control the population of green crabs in a small, isolated bay known as Seadrift Lagoon in California.
Extensive trapping efforts in the bay, Grosholz said, managed to reduce adult populations substantially over a few years. Then, a few years in, the population exploded to levels higher than they were before the eradication efforts began. Their study showed that predation from older, larger crabs actually serves to curtail the population in a significant way.
“There were so few adults in the habitat, basically all of the recruits that landed pretty much survived,” he said.
The secret to population control, they found, isn’t to completely eradicate them all, it’s to get the number to a manageable level.
“We now have a citizen science trapping program in place that will maintain the green crabs at the 20 or 30 percent of what we call the carrying capacity,” Grosholz said. “It’s not fished down to the point where we may get those massive recruitment events going.”
While that approach is promising, Brian Beal of the University of Maine at Machias says his findings after research have concluded that any form of population control on the coast of Maine is going to be an uphill battle, if it’s even possible.
“We’re talking about the coast of Maine, it’s not a closed system,” he said. Comparing green crab to other populations that have been reduced by human intervention is a false equivalence, he added, as most of those other species were endemic, while green crabs are invasive.
“I think trapping and mitigation is something we say to feel good," Beal said.
For Bradt, whether or not the tide of green crabs can be stopped is only part of what the working summit was all about. Creating a new market for the crabs to allow for an economic incentive to catch them could be a way to adapt to the changing climate.
“We wanted to bring all these different people here who have these different ideas,” she said. “Let’s flip this problem on its ear.”
