Hard clam farming in eastern Maine: field experiments to evaluate biological & economic efficacy of field-based nursery and grow-out phases
We have discovered the easternmost commercial population of hard clams, Mercenaria mercenaria (L.), in the U.S., in the waters of Eastern Maine. In 2007, we received permission from the State of Maine to lease a 6-acre tract in the shallow subtidal of Goose Cove (Trenton) to farm cultured hard clams. This is the first-ever lease of this type in eastern Maine. Working with our research partners from the Downeast Institute for Applied Marine Research & Education in the town of Beals, we received Phase I USDA SBIR funding to examine seasonal growth and survival of cultured seed (6-12 mm shell length, SL) at multiple sites in eastern Maine from Trenton east to Cobscook Bay. That effort demonstrated unambiguously that the waters of far eastern Maine (Washington County) are too cold, and predators such as moon snails and green crabs too numerous to undertake farming operations in that region. Survival and growth of cultured seed in Goose Cove, however, was excellent in small plots where seed was planted in mid-Spring and protected with flexible netting. We observed > 85% survival through December, with animals attaining SL > 20 mm. We propose to extend our experimental approach to larger, pre-commercial scales to test hypotheses concerning both spatial and temporal variation in cultured hard clam growth and survival during the nursery, overwintering, and grow-out phases at Goose Cove and sites west of there in Hancock County. Specifically, we wish to determine what configuration of a field-based nursery system, and which nursery locations, will allow us to produce the largest transplantable hard clam seed; what the most efficient method is to store pre-planting size seed over the winter to optimize survival and growth; what field grow-out methods will produce market size animals in the most effective and efficient manner; and, to what degree interannual variability plays in hard clam growth and survival, both in the field nursery and grow-out phases. Answers to these questions will affect plans to commercialize our rearing methods and procedures.
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