Downeast Institute, Maine Soft Shell Clam Improvement Effort

Downeast’s Mission: 

To generate new knowledge of the marine ecosystem for all who depend on it..

Grant Project Goal(s):

To create a new mindset amongst clammers and local clam stewardship committees to think and see beyond traditional approaches to conserve the resource.

Background:

The Maine soft-shell clam (Mya arenaria) fishery was worth $16 million in dockside revenues in 2013, making clamming the third most valuable commercially harvested species in the state. Nearly 100% of the harvest originates in the intertidal zone, where clammers use short-handled, tined forks or hoes to excavate clams from 10-15 inches deep in muddy or sandy sediments.

Most of the 2013 landings from Maine represent a subsidy from the upper intertidal, where, historically, clammers rarely dig because clams there are generally small, slow-growing, and contain less meat than clams found lower along the tidal gradient. The reason for the subsidy is that commercial clam populations cannot be found below the upper intertidal due to an explosion of the invasive crustacean, the green crab, Carcinus maenas.

Although green crabs have been residents of the Maine coast for nearly 115 years, their population densities seem to correlate directly with seawater temperatures. During the past three years, seawater temperatures along the Maine coast have risen dramatically, and as this has happened so, too, have green crab populations, especially in the southern one-third of the coast. The presence of green crabs at high levels is complicating traditional clam management schemes that towns rely on to maintain commercial clam populations.

Immediate Objective(s):

To conduct large-scale, manipulative experiments to test hypotheses involving predator exclusion and habitat modification designed to enhance locally the number of both wild and cultured “spat” (juvenile clams).

Key Learnings:

Learn more at Downeast Institute, Maine Soft Shell Clam Improvement Effort