icantly affected by salinity. At near optimum salinity these larvae survive 

 and grow over a significantly wider range of temperature than at salinities 

 near the lower limits of tolerance. - J.L.M. 



439 



Davis, H. C. 1968. 



Shellfish hatcheries present and future. Am. Fish. Soc, Ann. Meet. 

 1968. 98: 18 (abstract) . 



Data were given on food, temp, salinity, pH, and other requirements of 

 larvae of Meraenaria meraenaria and American oyster, and susceptibility 

 of these larvae to toxins and pathogens. Progress was reported on 

 development of genetic strains and in culture methods to increase pro- 

 duction in open waters. - modified author's abstract - J.L.M. 



440 



Davis, Harry C. 1969. 



Shellfish hatcheries - Present and future. Trans. Am. Fish. Soc. 98(4): 

 743-750. 



Some shellfish biologists and commercial producers believe that a new age 

 in shellfish culture is at hand. Efforts to increase shellfish production 

 date back to the Roman Empire. Hatchery and laboratory rearing are about 

 50 years old. Salinity, temperature, and pH tolerances are reasonably well 

 known. Hard clam is not very tolerant of low salinity. Eggs will not 

 develop to straight-hinge stage at salinities below 22°/°°. Larvae can 

 survive and grow reasonably well at 17.5V 00 or somewhat below. The pH 

 range for clam larvae must be kept between about 7 and 8.75. Pollution of 

 various kinds must be avoided also, although clam larvae are somewhat more 

 tolerant than oyster larvae. Larvae do better on some foods than others, 

 and some forms produce toxic metabolites. Growth and survival of clam 

 larvae are satisfactory over a fairly wide range of water temp, at least 

 from about 17.5 to 30°C. Diseases can be prevented by rigid attention to 

 cleanliness, but much more needs to be known about causative agents and 

 their control. Genetic studies are needed to improve growth rates, 

 disease resistance, meat content, and tolerance to various physical factors. 

 Relatively high costs of hatchery production must be reduced by obtaining 

 highest possible survival. Predator control will be necessary once 

 juveniles are planted in natural environment. Possibilities also exist for 

 utilizing warm water from power plants, and using shellfish to harvest 

 phytoplankton in final sewage treatment ponds. - J.L.M. 



441 



Davis, H. C. 1971. 



Design and development of an environmental controls system for culturing 

 oyster larvae. . Artificial Propagation of Commercially Valuable Shellfish. 

 Univ. Del., Newark, p. 135-150. 



SUNY - Stony Brook library reported that after considerable searching they 

 were not able to locate or verify this title. Because it does not necessarily 

 relate to Meraenaria meraenaria search was terminated. - J.L.M. 



442 



Davis, Harry C. (undated) . 



The effects of different salinities and temperatures on oysters and clams. 

 Appendix F, U.S. Fish Wildl. Serv., 15 p. 



Salinity range for development of straight-hinged clam larvae from embryos 

 ranged from 20.0 to 35.0°/°° with an optimum of 26.0-27.5°/°°. Optimal growth 

 of clam larvae occurred at 26.0-27.5°/°° or higher. The lower limit for 

 larval growth for practical culture was 20.0°/°°. Juvenile clams (7.3-7.6 

 mm long) grew best at salinities of 26.0-27.0°/°°. Embryos developed into 

 straight-hinged larvae within the temperature range 15 . 0°-30. 0°C . Development 

 was best between 23.0 and 25.0°C. Growth of larvae beyond the straight-hinged 

 stage increased with increasing temperature in the range 15.0°-32.5° or 

 33.0°C. Optimum growth for newly set clams occurred from 20.0° to 25.0°C. 



123 



