The future of Maine’s softshell clam industry may depend on farming them rather than harvesting the shellfish in the wild, according to scientists and clam diggers who collaborated on a recent research project.
A new study, conducted over two years at dozens of locations along the state’s southern coast, indicates that predators are the single biggest reason Maine’s softshell clam population has declined sharply in recent years. Raising clams in enclosures that protect them from being eaten by other creatures could go far in boosting the number of clams harvested in the state, according to researchers.
For over a month now, Freeport clammers have been trapping green crabs in the Harraseeket River of Casco Bay. In this video, MCA president Chad Coffin explains current green crab conditions.
Posted by Maine Clammers Association on Friday, 6 June 2014
“Clammers today are hunter and gatherers,” Brian Beal, a marine ecology professor at the University of Maine at Machias and co-author of the study, said Tuesday. “[The future of clamming] doesn’t look like hunting and gathering. It looks like farming.”
Beal, who also serves as director of the Downeast Institute for Applied Marine Research and Education in Beals, over the past few years has worked with clam diggers and the Maine Clammers Association to try to identify specific causes for the decline in softshell clams.
Softshell clams, which support a $12 million fishery in Maine, face a variety of challenges as the Gulf of Maine grows warmer as a result of climate change — increased temperatures and acidity, biotoxins and pollution among them. But what the researchers found is that the biggest culprit by far in the decline of of the bivalve shellfish species along Maine’s coast are green crabs and milky ribbon worms, which eat the clams by injecting toxins inside them and then sucking out their innards.
Milder winters resulting from climate change have allowed these predators to proliferate along the Maine coast, and the impact they have had on softshell clams has been severe. In some parts of Casco Bay, mud flats once known to produce clams have become known as “ dead muds” because of the absence of marine life.
According to Beal, the study showed mud flats can produce clams when predators are kept out. When he and other researchers placed square wooden boxes with mesh coverings on the tops and bottoms on the mud flats, tiny clams accumulated and grew in the boxes, often by the thousands. Water quality and other environmental conditions where researchers placed their boxes did not appear to be limiting factors.
“They are not deserts,” Beal said of open mud flats where diggers have come up empty. “They are alive and [can be] highly productive.”
Chad Coffin, a clam harvester from Freeport and co-author of the study, said Wednesday that the problem’s extent has been obscured by the fact that the number of clam harvesters in the state has declined sharply since the early 1970s, from around 6,000 to roughly 1,500 now. Many still are getting decent catches, he said. And many believe that the fishery can continue to be managed effectively by seeding mud flats with “spat,” or tiny clams, limiting the number of harvester licenses, and hoping for more frequent cold winters instead of by finding ways to control predation.
The number of tiny clams that settle on the mud flats “isn’t the issue,” said Coffin, who also is head of the Maine Clammers Association. “Everything is getting eaten.”