Juvenile and yearling growth of Atlantic surfclams Spisula solidissima (Dillwyn, 1817) in Maine

With the recent emergence of a shellfish aquaculture industry in Maine, the development of alternative species would provide mariculturists some flexibility and stability by diversifying their product line and opening up coastal environments unsuitable to the oysters and mussels currently being cultivated. The Atlantic surfclam, Spisula solidissima, occurs naturally in Maine, and although it has not been commercially exploited, this mactrid clam may provide growers with a profitable new product line. What is not known is how well this species will grow in a culture setting throughout Maine's diverse marine environment. The goal of this study was to assess the growth and survival of two age/size classes of Atlantic surfclams under a variety of growing conditions. Juvenile (3-mm) and yearling (23-mm) surfclams were reared for one growing season in floating screened trays and intertidalsediments, respectively, at six study sites along the coast of Maine. After 4 mo of growth, mean size differences of juveniles among the six growing sites were significant. Juveniles reared at the upper Damariscotta River site grew the fastest (8.9 mm. shell length [SL] among the six sites. In comparison, those grown in Mud Hole Cove had the slowest growth (5.5 mm SL). Yearling surfclams at both planting densities grew the fastest in the Mud Hole Cove plot (40 mm SL) compared with the slowest growing sibling cohorts in the Deer Isle plot (27 mm SL). Similar trends among plots were observed with respect to both wet and dry weight gain. Surfclams reared in low-density treatments tended to grow faster than the high-density cohorts, although the means were not significantly different at any of the study plots. The optimal nursery sites for juvenile growth were different from the most productive areas for yearling growth, suggesting that growers may want to choose separate areas for different culture phases. This study is the first to document rates of growth and survival of Atlantic surfclam [ABSTRACT FROM AUTHOR]