Young clams are graded after spending their first year 



A I^ew Bag 

 qf Tricks for 

 Clam Farmers 



By Cynthia Henderson Vega 



in oa?s. 



W, 



/ant to know how to keep a clam as 

 happy as, well, a clam? Mark Hooper's got it 

 in the bag. 



With support from the Fishery Resource 

 Grant program (FRG), Hooper is using bags to 

 dramatically increase the survival of hard 

 clams during the first critical year of grow-out. 

 His findings could make other North Carolina 

 clam mariculturists happy, too. 



For their first year, tiny clams are taken 

 from the protective environment of the nursery 

 and planted in the bottom beds of open waters 

 — where the wild things are. 



The clam nursery at Hooper Family 

 Seafood is a series of raceways on a dock on 

 the Core Sound in Smyrna. A great blue heron 

 lifts noiselessly from its hiding place near the 

 clear water's edge. It's peaceful, but beneath 

 the water's surface. . .it's a jungle in there. 



Blue crabs, mud crabs, snapping shrimp 

 and whelk are a few of the things that go 

 chomp in the night — or any time, for that 

 matter. Typically, Hooper says, clam farmers 

 try to protect young clams by covering them 



with polypropy- 

 lene mesh. Even 

 this protective 

 covering, 

 however, cannot 

 prevent the 50 

 percent mortality 

 that is common 

 the first year. 

 The statistics are 

 daunting for 

 anyone 



considering clam 

 mariculture as an 

 alternative to 

 harvesting from 

 increasingly 

 pressured wild 

 stock. 



In Florida, 



mariculturists found a way to beat the odds, 

 decreasing mortality by raising clams in 

 tented mesh bags. Now, according to Leslie 

 Sturmer. Sea Grant shellfish aquaculture 

 extension agent at the University of Florida, 

 the bag method is the only way clams are 

 raised and harvested there, bringing in around 

 $12.7 million annually. 



Sturmer says other states have tried to 

 follow Florida's example, but most have been 

 unsuccessful. The farther northeast the state, 

 she says, the less effective the bag system is. 

 She speculates that Florida's success may be 

 because the warmer climate means a shorter 

 grow-out period — 1 2 to 1 5 months. In North 

 Carolina grow-out periods are two years or 

 more. 



Hooper tested a variation of the Florida 

 system with his FRG project. He, too. had 

 problems. The clams grown in bags were 

 significantly smaller after the first year than 

 those grown in beds. But his success lay in 

 the survival rates of clams raised in bags. 



Hooper says "mortality is primarily a 

 first-year problem." That's when clams shells 

 are too thin to defend against the jaws and 

 claws of the deep. Bags protect newly planted 

 clams by forming four-by-four-foot tents 

 around them supported by center stakes of 

 1 2-inch long PVC pipes. The bags are 

 secured at the comers, with clams piled in the 

 centers. 



Clams don't grow as large in this 

 maricultural tent city — possibly because of a 

 decreased flow of nutrient-carrying water to 

 the bivalves or because of competition for 

 food. In nature, clams feed by burrowing 

 under the substrate. Siphons extend up, taking 

 in plankton and microorganisms carried along 

 by water currents. 



It takes valuable growing time for 

 sediment to accumulate in the bottoms of bags 

 and simulate a natural environment. So clams 

 grow more slowly, but, because they are 

 protected from predators, more survive. 



Hooper has found 13 mm to be an 

 optimal planting size. That's bigger than the 

 diameter of a number-two pencil, smaller than 

 a dime. Planted in bags at this size, his clams 

 had an impressive 90 percent survival rate. 



The Hooper variation combines the bag 

 and bed methods, increasing survival with 

 bags the first year, then planting in beds the 

 second year to catch up in growth. The 

 method has proved so successful, Hooper says 

 he now uses it exclusively. 



The bag/bed method has the additional 

 benefit of allowing Hooper to grade the clams 

 before planting them in beds. When clams are 

 harvested with the bed method, those too 

 small to be sold are replanted to keep growing. 



Now when Hooper pulls his bags up 

 after the first year, he separates them and 

 plants similar sizes together. He saves final 

 harvesting time by starting with beds where 

 the largest clams were planted. 



In a current FRG project. Hooper is 

 investigating this grading system in order to 

 improve shellfish crop management. It's a 

 matter of one good project leading to another. 



Hooper wades into his clam beds staked 

 off in the glistening sound. A gull laughs 

 raucously as Hooper gently rakes up 175 

 clams to fill an order. It doesn't take long. He 

 picks up a perfect, nicely rounded specimen 

 and proudly points out the smooth white edge 

 that, he says, "indicates a good year's growth." 



On the dock, a few small terrapins peek 

 up from a watery containment. Hooper is 

 interested in ways to prevent terrapin 

 entrapment in crab pots. Another FRG 

 project? Could be. As Hooper says, 

 "We've got a lot of ideas around here." □ 



COASTWATCH 19 



