Evaluating subtidal and intertidal grow-out methods for cultured hard clams in eastern Maine: a series of manipulative field experiments

Egypt Bay Aquafarms and its non-profit aquaculture incubator/research partner, the Downeast Institute for Applied Marine Research & Education (DEI) seeks to determine the feasibility of developing effective methods to farm hard clams, Mercenaria mercenaria, subtidally in eastern Maine using hatchery-reared juveniles obtained from wild, local broodstock. Hard clams occur at very low densities from the low intertidal to shallow subtidal zone in Maine's easternmost counties of Washington and Hancock where they support a small, commercial fishery (ca. 5-10 seasonal harvesters). The potential exists here to develop farming techniques on leased grounds to produce commercial quantities of littlenecks and top necks to fill existing orders locally, and expand the business to mid-coast and into southern Maine. Hard clams (quahogs, top necks, cherrystones) are popular among out-of-state tourists visiting coastal Maine, but supplies from wild stocks cannot meet existing demands. Preliminary growth studies from a subtidal population of wild hard clams near Trenton, Maine indicate that 3 to 4+ years are required to reach market size. Growth rates may be faster with selective breeding; however, no information exists concerning field grow-out of cultured juveniles in cold-water environments. We will investigate the efficacy of several strategies for growing cultured hard clam seed (6-10 mm SL) during the first, and most critical, eight months (May to December 2008) using techniques that compliment those used successfully to culture individuals of Mercenaria in other states. If we can develop efficient field methodologies to grow juveniles to market size, we would eventually produce a practical guide or technical bulletin to share this information with other entrepreneurs. Because Maine law does not restrict the size of cultured shellfish, it may be possible to develop local markets for hard clams that are smaller than little necks (i.e., 25 mm thick) such as "pasta necks" (16-19 mm thick) or "petite necks" (20-22 mm thick). Our work will play a significant role in helping us understand what limits growth and survival at a variety of intertidal and shallow subtidal sites in eastern Maine. Our results will enable Egypt Bay Aquafarms to develop systematically a dynamic management strategy for growing hard clams that is responsive to the vagaries of market forces and trends. The expected outcomes are that we will contribute to the base of knowledge concerning the efficacy of various growout techniques of cultured individuals of the hard clam in eastern Maine. Results will enable us to decide whether it is biologically and economically feasible to grow hard clams to market size in eastern Maine. If so, the impacts of our work will be widespread, as others will follow, which will stimulate local economies. The anticipated benefits of our work will enable others to choose effectively whether it is feasible to farm hard clams in eastern Maine.