and concluded that much information necessary for controlled culture is 

 not available, or is inferential at best, especially for Mereenaria 

 mereenaria. Much more basic biological information must be gathered if 

 design of workable culture systems is to succeed. "Close to nature" 

 culture is technologically easier, and much present mariculture has 

 followed this route. (Abstracter's note: This is a review paper, and 

 details have not been given in this abstract because they are contained 

 in abstracts of papers consulted by the authors, which also appear in 

 this bibliography if they contain original information on hard clam. 

 Inferences and comments on hard clam in the paper above which were not 

 taken from the literature are summarized here: We can conclude that there 

 is a range of algal cell concentrations wherein clams can filter most 

 efficiently. This range will be different for each algal species, 

 depending on size of algal cell and effects of its metabolites on the 

 mollusk. Total inhibitory effect of a mixture of algae may be different 

 from that of component species. Literature contains several quite 

 different assessments of total amount of food eaten by clams and oysters. 

 The animals appear to remove more cells from flowing than from standing 

 water. Results of laboratory studies imply that they eat more than has 

 been estimated from field experiments. There are no reported studies of 

 respiratory quotient for hard clam, but there is no reason to suspect 

 that it is very different from that of Crassostrea virginica , which was 

 calculated byGaltsoff as 1.00 for carbohydrate, 0.79 for protein, and 

 0.71 for lipid, or a mean RQ of 0.85 ± 0.24. The authors found no 

 published report on quantities of nitrogenous wastes excreted by hard 

 clam, but assuming that the ratio of production of ammonia in a 100-gram 

 clam is similar to that of American oyster they derived the following 

 formula: log Qnh 3 =-0.344 log W - 0.234, where Q.NH3=micromoles NH3/g 

 whole weight/hr at 25°C and W=whoIe weight (wet) . Information on deposition 

 of solid wastes does not exist for hard clam. The authors considered that 

 total ammonia nitrogen may be safely maintained at 10 ppm in clam culture 

 systems. There have been no studies of high levels of nitrates on marine 

 organisms. The authors give a conservative estimate of upper limit of 

 tolerance to nitrate for hard clam as about 325 ppm. They believe that pH 

 should be maintained in a clam maricultural system above 7.8. Specific 

 types of organic compound occurring in recirculated sea water are poorly 

 known, as are their physiological effects on bivalves. Growth of M. 

 mereenaria at temperatures above 23°C is not known, nor is the effect of 

 temperature upon growth when quality and quantity of food is controlled. 

 There is not sufficient information on filtering rates of hard clam of 

 various sizes, nor on relations between biodeposition and body size. There 

 have been no studies on effects of varying concentrations of ammonia, 

 nitrites, or nitrates on clams. Latest literature citation is 1975, 

 which suggests that the review is up to date through 1974 .) - J.L.M . 



558 



Epifanio, Charles E., Gary Pruder, Michael Hartman, and Richard Srna . 1973. 



An interdisciplinary study on the feasibility of recirculating systems in 

 mariculture. Proc . 4th Annual Workshop, World Mariculture Soc . Louisiana 

 State Univ., Div. Continuing Education, Baton Rouge, p. 37-52. 



Once the biological filter was conditioned and the start up procedure docu- 

 mented, 20,000 juvenile hard clams, Meraenaria mereenaria, were introduced. 

 The clams are held on screened baskets . They are fed at an algal concentra- 

 tion of 25,000 cells/mi.. Platymonas sp., Carteria sp. , Nannoehloris aeulata, 

 and Phaeodaetylum tricornutum were used as food. The carrying capacity of 

 the system has not yet been determined. The tank was designed only for 

 rearing juveniles smaller than 4 mm in width. - J.L.M. 



559 



Erspamer, V., and F. Ghiretti . 1951. 



The action of enteramine on the heart of molluscs. J. Physiol. 115(4) : 

 470-481. 



