301 



Castagna, Michael, and John N. Kraeuter. 1977. 



Mereenaria culture using stone aggregate for predator protection. Proc. 

 Natl. Shellf. Assn. 67: 1-6. 



The most serious problems in field maintenance of seed clams are predation 

 and loss by current and wave action. Larvae were raised by standard 

 hatchery techniques, which are described in some detail. Clams were held 

 after setting for about 6 weeks or until they grew to 2 mm. They were then 

 placed on plots covered with 4 cm of 1- to 3-cm chips of crushed stone 

 aggregate. Protection against current and wave action was provided by 

 baffles of steel rod and plastic screen, also described. Larger predators, 

 mostly blue crabs and rays, were held out with a net 2 m high. Annual 

 production of hatchery seed ranged from 12 to 55 million newly set clams. 

 Survival to field size was 15% to 20%. Littleneck size was reached in 22 

 to 28 months. Cost for 600,000 clams planted in the field was 1.54/clam, 

 including estimated interest on a loan to provide hatchery, labor, utilities, 

 and all supplies. Other costs would be maintenance of field plots for 2 yrs , 

 about l/2C/clam, and harvesting, about 0.2^/clam. Current market value of 

 prime-sized littleneck clams was about 5C/clam. Survival was in excess of 

 75%. Economical commercial operation would be possible with 40% survival. 

 Further reductions in costs are possible. - J.L.M. 



302 



Castagna, Michael A., Lawrence W. Mason, and Fred C. Biggs. 1970. 



Hard clam culture method developed at VIMS . Aggregates on bottom protect 

 seed clams from predators. Va. Inst. Marine Sci., Mar. Resour. Adv. 

 Ser. 4, 3 p. 



Predators destroy almost all unprotected clams smaller than one inch. Blue 

 crab is the major predator in Virginia, but other crabs, boring snails, 

 bottom-dwelling fishes, and waterfowl also are responsible. Quahog requires 

 waters of moderately high salinity, where these predators abound. This 

 often prevents successful natural reproduction. Methods of protection have 

 included planting clams in screened trays or boxes, within fenced enclosures, 

 under sheets of netting or hardware cloth, in saltwater ponds or tanks, and 

 intertidally . These techniques are unreliable, expensive, and cause silting 

 and slow growth. The new method spreads shell, gravel, or other materials 

 called aggregates over the bottom before planting. Preparation of bottom is 

 simple, there is no maintenance, and increased yields should soon pay for 

 initial cost of aggregate. The technique promises to encourage operation of 

 clam hatcheries. Tests with Mereenaria mereenaria showed that 80% to 90% or 

 more of seed clams survived through seasons in which blue crabs and other 

 predators were most active. Survival of unprotected controls was about 16% 

 and never more than 30%. Clams as small as 1/25 to 1/5 inch survived well 

 in some plantings, but those larger than match-head size did best. Smaller 

 clams were too active and would leave the protection of the aggregate. 

 Tests were to be continued. - J.L.M. 



303 



Castagna, Michael A., Lawrence W. Mason, and Fred C. Biggs. 1971. 



Hard clam culture method developed at VIMS. Comm. Fish. News, Fish. Nildl. 

 Admin. Md. 4(1): 2,4. 



This is essentially the same article published in 1970 in VIMS Marine 

 Resources Advisory Series No. 4, and abstracted above. Recommendations 

 were: 1) select aggregates that are cheap and plentiful in the area; 2) 

 particles should be heavy enough to sink and remain on bottom, and small 

 enough to pack well; 3) coarse materials should be spread to a thickness 

 of 1 to 3 inches if coarse, 1 to 2 inches if fine; 4) scatter seed clams 

 evenly over the aggregate at 2 5 to 50 clams/ft2; and 5) plant when clams 

 are active, e.g., when water temp is 48°F or higher, and plant at slack tide. 

 - J.L.M. 



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