472 



Dexter, Ralph W. 1947. 



The marine communities of a tidal inlet at Cape Ann, Massachusetts: A study 

 in bio-ecology. Ecol . Monogr . 17(3): 261-294. 



473 



Dexter, Ralph W. 1968. 



Distribution of the marine molluscs at Cape Ann, Massachusetts. In Proc. 

 Symp. Mollusca, Pt. 1. Mar. Biol. Assn. India, Mandapam Camp: 214-222. 



Annual surveys were made in summers of 1933-37 and 1956-61. Two species, 

 Crassostrea vivginioa and Mevoenavia mercenavia , had been introduced, but 

 without much success. Winters usually are too cold for survival, and water 

 temp too low for reproduction. Hard clam is not mentioned in lists of 

 species collected. - J.L.M. 



474 



Dey, N. Dean. 1980. 



Growth of sibling hard clams, Mevcenaria mercenavia, in a controlled envi- 

 ronment. Natl. Shellf. Assn., Abstracts, Technical Sessions: 22 (abstract). 



Sibling populations of clams were raised in a controlled environment with 

 excess algal food. Within each population wide variations among individuals 

 were observed in shell length and volume. Populations were divided at an 

 early stage into five successively larger size classes. Clams in the larger 

 size classes always grew at a much more rapid rate than smaller clams at 18° 

 and 25°C. Sibling populations in the laboratory show an obvious non-normal 

 distribution of shell length within a few days of spawning . Early-setting 

 clams grow at a more rapid rate than late-setting clams, but make up only a 

 small fraction of the population. The size-frequency distribution of a 

 sibling population maintained in the laboratory is strongly skewed toward the 

 larger sizes. This is observed in hatchery-raised populations for at least 

 a year after setting, indicating that the late-setting clams never match the 

 growth rate of early-setting clams, and consequently remain small relative 

 to the larger siblings. Growth of clams after setting for the first two 

 months has three distinct periods. During the first 4 weeks growth con- 

 tinues at the larval rate. This rate of increase then decreases (growth 

 pause), perhaps associated with growth of siphons, for about two weeks. 

 Following the growth pause, rapid growth resumes, although at a somewhat 

 reduced rate. With proper selection of early-setting larvae fast growing 

 commercial strains, or uniform groups of clams, may be produced for work in 

 toxicology and nutrition. In hatchery operations, where initial numbers 

 are large, fast-growing larvae make up fewer than 5% of the population. - J.L.M. 

 - J.L.M. 



475 



Dey, N. Dean, and Ellis T. Bolton. 1978. 



Tetracycline as a bivalve shell marker. Proc. Natl. Shellf. Assn. 68: 77 

 (abstract) . 



Mercenaria mercenavia was exposed to tetracycline dissolved in filtered sea- 

 water to which algal food was added. Marking was vague at 0.5 and 5.0 mg L 

 but vivid at 25 to 200 mg L . No deaths or morphological defects were noted. 

 Algal species known to be good food sources produced the greatest incorpora- 

 tion of tetracycline. Tetracycline phosphate complex produced the best 

 results. Tetracycline is useful in studies of shell growth and morphology 

 and in field investigations. The technique could be used as an identifica- 

 tion to combat poaching on leased grow-out grounds. - J.L.M. 



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