requirements have been met. Five species were finally selected, of which 

 Meraenaria meroenaria was one. Commercial production through aquaculture is 

 at least marginally feasible, and can be expected to attract more producers, 

 provided that adequate bottoms are available for lease. A large human 

 population accustomed to eating clams exists in New England. Thus, consumer 

 resistance to increased production might be relatively easy to overcome. In 

 certain respects this species may be more readily cultured than other 

 commercial mollusks. Adults held at slightly below 20°C may be induced to 

 spawn at almost any time. Fertilized eggs are rather sensitive to low 

 salinities and fail to develop in water below 22°/°° • Larvae are hardier: 

 optimum salinity is about 27°/oo (range about 15 to 30°/°°) • Optimum temp 

 is 25 to 3 0°C. At 3 0° setting may begin in 7 days after spawning. Larvae 

 are also less particular in food requirements than oyster larvae, also less 

 sensitive to pollutants. Juveniles have voluminous food requirements and 

 culture of food does not appear to be practical for these stages. Juveniles 

 will survive well in nature if protected by fencing or aggregates. Commercial 

 clam rearing facilities for larvae probably must rely on large volumes of 

 living diatoms or naked dinof lagellates. Some Chlorella may also be used. 

 The major technical problem is provision of enough food for postlarval stages. 

 Hard clam does not grow rapidly, and takes a minimum of 2 yrs to grow to 

 market size. Culture of juvenile clams to market size under totally 

 artificial conditions would require very large amounts of phytoplankton and 

 culture under these conditions has not been reported in detail. It would 

 seem far more practical to grow these stages in the natural environment. 

 This creates some problems in New England, because the natural continuous 

 range of the species is from Cape Cod southward. To the north, populations 

 are restricted to areas where local seasonal warming of water permits 

 spawning. Even in southern New England setting intensity may be highly 

 variable. Thus, hatchery culture probably would be a necessary adjunct. 

 Predation on juveniles is a serious problem, and some form of protection 

 probably would be necessary. Feasibility of large-scale fencing has not 

 been demonstrated. Slow growth, especially in colder areas, might require 

 3 or more yrs until harvesting. Culture in a controlled environment 

 probably would be too costly. Not enough information was available to 

 estimate costs of culture in a natural environment. It was suspected that 

 the degree of profitability is highly variable, and that existing operations 

 are of marginal profitability at present. The picture could improve with 

 rising prices. Political and social climates for assertion of exclusive 

 culture rights in natural areas are not particularly favorable. To compete 

 successfully with other industries, activities, and uses or misuses of the 

 environment, aquaculture must demonstrate long-term viability and social and 

 economic benefits. Its failure to do so has come from inadequate technology 

 and unfavorable socio-political climates. Public action to provide 

 opportunity is needed. Recommended are: pilot plants, use of domestic 

 wastes, understanding of water quality tolerances, and provision of areas of 

 high quality for culture. - J.L.M. 



639 



Gaucher, Thomas A. 19 70. 



Thermal enrichment and marine aquiculture. In Marine aquiculture. William 

 J. McNeil (edj . Oregon State Univ. Press, p. 141-152. 



The only specific mention of Mercenaria meroenaria is with reference to the 

 work of the University of Southampton in Great Britain, where three waste 

 products (C0 2 gas, domestic sewage, and heated water) were used in a com- 

 bined algal and shellfish culture system to produce a useful product, at 

 the same time substantially reducing the polluting effects of the wastes. 

 Exposing clams to artificially warmed water creates characteristics in the 

 population similar to those in populations occurring southward in the geo- 

 graphic range. - J.L.M. 



178 



