Maine’s clamming industry, typically the second or third most economically important marine resource, saw landings fall to an 87-year low in 2017. Commercial harvests dropped 39 percent and 66 percent over the past five and 35 years, respectively. Today, about 1,500 state-licensed clammers ply their trade in the soft-bottom intertidal zone whereas in 1973 that number was nearly 5,925. This decline should worry coastal communities from Kittery to Lubec.
Though we possess different perspectives and experiences, we are united in our concern for the future of Maine’s clamming industry. We joined forces on the flats in northern Casco Bay to better understand the nature of the clam decline. Since 2013, we have worked together, along with other clammers, research technicians and students, to conduct 27 experiments at 78 intertidal sites, and analyzed the contents of more than 34 tons of intertidal sediments. Some of our findings were recently published in the Journal of Shellfish Research.
While many threats to soft-shell clam populations exist, such as disease, pollution, red tide, coastal acidification, our studies showed that predators — both invasive and native — are the major cause of recent declines in this fishery, and furthermore, that no significant relationship exists between harvesting and the amount of juvenile clams under 1-year-old. Instead, we have learned that the health of the clam population is determined very early in a clam’s life history.
The major culprits are invasive European green crabs and native milky ribbon worms. Populations of both invertebrate predators are exploding, coinciding with steadily increasing seawater temperatures in the Gulf of Maine. One of the most important results from our 5-year investigations revealed that vast areas of “dead mud” — intertidal mud with few to no juvenile or adult clams — are, in fact, highly productive. When we excluded or deterred both large and small predators — worms, crabs, humans, birds, fish — from these apparent biological deserts, we discovered as many as 3,000 clams per square foot had settled, survived and grew during the trials.
Can anything be done to stem the tide before we lose one of Maine’s most iconic and valuable fisheries? Our investigations have shown that it is possible to adapt to the changing environment by protecting clams from predators. Adaptation may look more like husbandry and farming than hunting and gathering.
Unfortunately, coastal communities with clamming habitat often do not have the resources to protect hundreds to thousands of acres of intertidal flats from predators. They do, however, have the option to set aside up to 25 percent of this acreage to lease to creative and enthusiastic individuals in 2- to 5-acre plots to manage by planting clam seed and installing and maintaining predator protection. This is similar to what an oyster or mussel farmer does in deeper waters.
We have not given up on traditional clamming, but our findings show that we must adapt the fishery to the changed environmental and biological conditions. This will require extraordinary measures that challenge management practices still clinging to a time when coastal winters were long and bitter cold, and when ice left the rivers and heads of coves in early March rather than late January or even earlier. In the warming seawater, settling clams now face armies of predators in their quest for survival.
New clam management measures need to be instituted with a goal of increasing clam numbers enough to swamp out predation. These include: 1) abandoning the 2-inch size requirement for clams in favor of a maximum (3.5 inches) and new minimum (1.5 inches) size limits for harvesting, which is similar to measures in both the lobster and sea urchin fisheries; and 2) setting up rolling 2-3 week regional closures from west to east along the coast during late May through early July to allow clams to spawn before being harvested. In addition, it’s time for communities that manage intertidal clam populations to be held responsible for testing the efficacy of their conservation programs and projects.
Finally, unlike every other commercially important marine fishery in Maine, the soft-shell clam fishery has no fund for applied research. A separate lobster and scallop fund exists for research and development programs that address resource restoration or conservation. There’s even a fund for research and management of the sea cucumber fishery.
Given the historic and economic importance of the fishery to Maine, this is a critical time for Maine’s Legislature to put a clam fund in place to encourage applied research focusing on adapting to a changing marine environment during a time when clam landings have ebbed to record lows.
Brian Beal is a professor of marine ecology at the University of Maine at Machias, and director of research at the Downeast Institute. Chad Coffin is a clammer and president of the Maine Clammers Association.