537 



Eldridge, Peter J. 1978. 



Comparative survival and growth rates of hard clams, Mercenaria mercenaria, 

 planted in trays subtidally and intertidally at varying densities in a 

 South Carolina estuary. Natl. Shellf. Assn., 70th Joint Ann. SINA-NSA Conv. 

 & Meeting, 18-22 June 1978 (abstract: page not numbered) . 



Clam seed were planted at densities of 290, 869, and 1,160/m 2 and these 

 densities were maintained throughout the experiment. Average size remained 

 similar from May through December 1975, then clams at the lowest density 

 grew faster ' than the others. At 290 clams/m 2 average length was about 45 mm 

 in 19 months. At higher densities clams took 9 months longer to reach that 

 size. Survival at 290/m 2 was significantly lower than at higher densities. 

 - J.L.M. 



538 



Eldridge, Peter J., Arnold G. Eversole, and Jack M. Whetstone. 1979. 



Comparative survival and growth rates of hard clams Mercenaria mercenaria, 

 planted in trays subtidally and intertidally at varying densities in a 

 South Carolina estuary. Proc . Natl. Shellf. Assn. 69: 30-39. 



Seed clams, Mercenaria mercenaria , were planted in subtidal trays subtidally 

 and intertidally at densities of 290, 869, and 1,159/m 2 . Densities were 

 maintained throughout the experiment. Average size was similar from May to 

 December 1975, then clams at the lowest density attained an average length 

 of about 44 mm 19 months after planting. Clams at intermediate density grew 

 slower, and clams at highest density grew slower yet, taking approximately 

 12 months longer to reach an average length of about 4 4 mm. Survival was 

 higher subtidally than intertidally. Survival of clams in the lowest density 

 treatment was significantly lower than at higher densities. Panopeus herbstii 

 was the most abundant predator. Experiments showed that survival was posi- 

 tively correlated with increased average size and cooler water temperatures. 

 Shell or aggregate substrate and areas without extensive wave action or 

 shifting substrate also improved survival. Survival approached 90 to 95% by 

 the time clams had reached 16 to 17 mm average size. Clams averaging 13 mm 

 long, planted at a density 290/m 2 , can attain a mean size of 44 mm in about 

 18 months and 51 mm in 24 months. The following mariculture strategy was 

 proposed for South Carolina. First, select a suitable habitat, not exposed 

 to extreme wave action, and where clams are found. Next, creek bottom should 

 be covered with shells or similar aggregate at approximately one bushel/m 2 

 in summer. In fall, when water temperatures are between 15 and 18°C and 

 declining, clams 12 to 15 mm average size should be planted at approximately 

 300/m 2 . Clams should attain average size of about 45 mm in early summer of 

 the second year about 18 months after planting. The authors feel it would 

 be risky for a private investor to undertake such a project at present. But 

 a pilot project including economic feasibility would be a good candidate for 

 a governmental supported activity. - J.L.M. 



539 



Eldridge, Peter J., Wayne Waltz, and Holland Mills. 1976. 



Relative abundance of Mercenaria mereenaria notata in estuaries in South 

 Carolina. Veliger 18(4): 396-397. 



The best estimate of relative abundance of M. mercenaria notata was 1.23% 

 of total clams sampled, varying from 0.71 to 2.17% in individual samples. 

 This represents clams equal to or greater than 25 mm in width. It was 

 assumed that the ratio held true for smaller clams as well. - J.L.M. 



150 



