The Arctic surfclam, Mactromeris polynyma, is a relatively large bivalve (75 - 125 mm) that is similar in appearance to the more common Atlantic surfclam, or hen clam, Spisula solidissima. Its major distinguishing feature, and one that makes it particularly appealing as a culture candidate for consumption in both domestic and Asian markets, is a purple foot and mantle that turns red when cooked, similar to a lobster, crab, or shrimp. This species is marketed for human consumption both domestically and in Asia, where it is known as hokkigai. In addition, Mactromeris produces spisulosine (PharmaMar, ES-285), an anti-cancer agent isolated from its tissues that inhibits prostate cell growth. Previous research culturing this species by our company, although quite successful, left numerous questions that need answering before commercial development can proceed (Davis and Shumway, 1998). Parameters such as estimating its growth, survival, and biomass under commercial-scale, field growout settings are lacking and will be investigated in this study. This Research will 1) use innovative approaches to reduce losses of juveniles during winter months using technologies that have worked well with other commercially-important cultured bivalve seed; 2) investigate multiple methods to reduce losses of small juveniles in the field during the spring-fall growout period by controlling predation in field plots; and, 3) examine means to increase harvesting efficiency of cultured individuals through field studies on the interactive effects of stocking density, position along the shore, and size of planted individuals on clam growth and survival. Specific technical objectives include: 1) determining whether adults of Mactromeris polynyma can be conditioned to spawn in a hatchery setting; 2) determining the effects of sediments on growth and survival of cultured juveniles (ca. 3 mm SL) in a nursery field setting; 3) determining the effects of stocking density on growth and survival of cultured juveniles (ca. 3 mm SL) in a nursery field setting; 4) assessing the effects of planting season on growth and survival of plantable seed (ca. 10 mm SL); 5) evaluating how field plantable Mactromeris juveniles perform over the winter in high density holding containers that are used routinely to hold cultured juveniles of softshell clams, hard clams, and European oysters for spring plantings; 6) estimating the fate of cultured juveniles in on-bottom growout plots in the lower intertidal zone; 7) determining the effects of predators on growth and survival of culture Mactromeris juveniles; and 8) determining interactive effects of stocking density and clam size on the production of commercial size (> 40 mm SL) cultured individuals. Anticipated results of this work will provide the information needed to decide whether to pursue further development of this species. Potential commercial applications from completed Phase I and II studies would position our company to produce and market both juvenile and adult Mactromeris for the wholesale and retail restaurant sectors as well as potential becoming a seed supplier for an emerging aquaculture industry. OBJECTIVES: A) To determine whether adults of Mactromeris polynyma can be conditioned to spawn in a hatchery setting. The technical questions are: 1) What combination of marine phytoplankton, seawater temperature, and bivalve size will induce gonadal development of broodstock to provide ripe gametes for successful larval development and growth to metamorphosis 2) What is the success of larvae from artificially- vs. naturally-conditioned broodstock B) To determine effects of sediments on growth and survival of cultured juveniles (ca. 3 mm SL) in a nursery field setting. The technical questions are: 1) Is sediment necessary for normal development and growth of shell in cultured Mactromeris juveniles 2) If so, what volume of sediment is necessary That is, should nursery culture occur in netted, on-bottom field plots, or can it proceed in discrete, floating nursery trays that are routinely used with success to culture a variety of small, infaunal bivalves (e.g., Mya arenaria, Mercenaria mercenaria, and Spisula solidissima) C) To determine effects of stocking density on growth and survival of cultured juveniles (ca. 3 mm SL) in a nursery field setting. The technical question is: What number of small Mactromeris juveniles can be added to floating nursery trays or on-bottom plots to produce the largest and most cost-effective plantable size seed (ca. 10 mm SL) D) To assess effects of planting season on growth and survival of plantable seed (ca. 10 mm SL). The technical question is: Do juveniles that are seeded in on-bottom growout plots at the end of the nursery phase (October/November) perform as well as those that are seeded in the spring (April/May) E) To evaluate how plantable Mactromeris juveniles perform over the winter in high density holding containers that are used routinely to hold cultured juveniles of softshell clams, hard clams, and European oysters for spring plantings. The technical questions are: 1) Can juveniles held in cages without sediment in constant ambient flowing seawater survive for up to six months (November - April) 2) What is the interactive effect of bivalve size and stocking density on overwinter survival F) To estimate the fate of cultured juveniles in on-bottom growout plots in the lower intertidal (where animals will be exposed for period of 0.5 - 1.5 hr/day) vs. shallow subtidal (where animals will be constantly inundated). The technical question is: Will animals survive and grow as well in the lower intertidal as they will in the shallow subtidal G) To determine effects of predators on growth and survival of culture Mactromeris juveniles. The technical questions are: 1) What role do predators play in the culture of Mactromeris juveniles 2) If predators are important, what methods of deterrence should be used to maximize surfclam growth and survival H) To determine interactive effects of stocking density and clam size on the production of commercial size (> 40 mm SL) cultured individuals. The technical question is: What range of stocking densities and clam sizes will maximize growth and survival to commercial size
