Soft-shell clams (Mya arenaria) are part of the economic and cultural backbone of Maine’s coastal communities. Clamming employs the second highest number of fishermen (after lobstering) and steamers are an important local food. Since the 1980s, however, as water temperatures have warmed, statewide soft-shell clam landings have declined by 75% (Beal et al., 2016). Even with this decline, the state produces about 60% of the country’s soft-shell clams and typically ranks as one of the top three fisheries in the state in terms of economic value. In 2019 its dockside value was over $18 million, with the industry valued at $54 million with wholesalers, distributors, retailers, and restaurants included.

Since 1987, DEI’s applied research has focused on restorative ecology and increasing the survival rate of soft-shell clams in the intertidal zone. Over the past decade DEI has conducted extensive investigations into the cause of the soft-shell clam fishery decline. Repeated independent field trials have found that predation is the primary factor affecting soft-shell clam survival (Beal et al. 2018), and that warming water in the Gulf of Maine has created an environment that favors predators such as the invasive green crab and milky ribbon worm, which have decimated soft-shell clam populations.

DEI’s research has resulted in the development of predator exclusion practices to enable the fishery to better survive warming ocean waters. We continue to examine the effectiveness of a variety of methods used to protect shellfish from green crabs, enhancing soft-shell clam populations.

Intertidal Monitoring of Clam Recruitment, Growth and Predation

Since 2020 DEI scientists have worked with towns across Maine to understand how many clams and other commercially important shellfish are recruiting to their mudflats, how fast the recruits grow when protected from predators, how many clams are able to survive their first year of life, as well as information about green crab demographics. This effort is called the Clam Recruitment Monitoring Network, learn more about it here.