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Farming Hard Shell Clams

Trenton, ME

In February 2006, the Maine Technology Institute funded a request by DEI to examine the hatchery, nursery, and overwintering phases of hard clams, Mercenaria mercenaria. Typically, this species of clam is associated with a geographic region that stretches from Florida to Massachusetts.  There is, however, a small commercial population of hard clams in Frenchmen’s Bay in Hancock County. A clammer from Blue Hill, Mr. Joseph Porada, contacted DEI in December 2005 saying he wanted to pursue a hard clam farming venture in Goose Cove in the town of Trenton.  In its first business incubator project, the Institute helped Mr. Porada obtain three 2-acre experimental leases for the purposes of farming hard clams.  The photos show the efforts to produce and grow hard clam seed to planting sizes on Great Wass Island.

Upper left:  Adult, commercial size hard clams from Goose Cove, Trenton.

Upper right:  During the winter of 2006, DEI conditioned hard clam broodstock from Goose Cove to spawn earlier than normal. DEI accomplished this by growing cultured algae and feeding it to the broodstock over a 2-month period.

Lower left:  Hard clams were sandwiched between pieces of rigid netting and placed into tanks of seawater maintained at 70^oF from February to April. Then, animals were stimulated to spawn.  DEI staff raised the swimming larvae for 2 weeks in large tanks and then reared the juveniles to a size of approximately 2 millimeters.

Lower middle:  Once the hard clam juveniles reached 2 mm, DEI staff transferred them to wooden trays lined with window screening and took them to the Institute’s ocean grow-out site at Mud Hole Cove on Great Wass Island.  

Lower right: Dr. Brian Beal, DEI’s director of research, designed an experiment to examine the effect of stocking density on hard clam growth and survival.  Using a total of 80 trays, staff filled 20 trays each with 2,500, 5,000, 7,500 and 10,000 seed clams. The trays were at Mud Hole Cove from July through mid-November when the average size of the hard clams reached approximately 8 mm – a 6mm increase. Stocking density did influence final size.  Animals held at the lower densities (2,500 and 5,000 per tray) were slightly larger than those held at the higher densities.  Survival was nearly 100%.  The photo shows a handful of seed hard clams (about 250) from one of the trays at Mud Hole Cove in September 2006.