generating station has raised water temperatures by discharging saline 

 cooling water. This may have enhanced the environment for successful clam 

 spawning. The season of growth may have been extended by as much as a 

 month and the rate of growth in the growing season was about doubled. No 

 evidence of increased mortality was found. Greatest effects were noted in 

 things like growth and condition, which are important in commercial shell- 

 fish growing. The author suggests that these favorable conditions could 

 be used to advantage, combining them with hatchery culture and predator 

 control. - J.L.M. 



93 



94 



95 



Ansell, A. D. 1964. 



Experiments in mollusc husbandry. Fish. News Internatl. 3(3): 216-219. 



Laboratory experiments were conducted on Venus mercenaria fed with cultures 

 of Phaeodactylum triaornutum. The diatom was chosen because it is tolerant 

 to different and changing conditions, hence is relatively easy to culture. 

 As hard clams grow, rate of transport of water increases, so that a large 

 clam may pump up to 6 liters of water/hr. Below about 6°C most clams are 

 inactive, but above 9°C most are active. Rate of water movement increases 

 with temp within tolerance range of the animal. In winter, between Sept 

 and March or April, lack of food and low temps restrict clam activity. 

 Condition may remain fairly steady or fall slightly, and carbohydrate 

 reserves are used up gradually. When plankton is abundant in spring 

 response of clams varies with temp. Thus, if temp is too low, growth and 

 condition do not improve even if food supply is abundant. In warm water 

 from a power plant the period of growth is extended, growth is faster, and 

 condition and reproductive activity are affected favorably. By manipulating 

 water temp and augmenting food supply clams can be brought to marketable 

 size in half the time required under traditional methods. Possibilities 

 for such intensive culture, using warm water from power stations should be 

 studied on a larger scale. Seed can be produced in hatcheries. - J.L.M. 



Ansell, Alan D. 1967. 



Egg production of Mercenaria mercenaria. Limnol. Oceanogr. 12(1): 172-176. 



Hard clams from Southampton Water, England, were induced to spawn in the 

 laboratory. In two experiments the range of eggs spawned per female was 

 0.38 X 10°-18.83 X 10 6 and 0.58 X 10 6 -29.93 X 10&, respectively , and the 

 average number of eggs per female was 7.11 X 10 6 and 9.28 X 10 6 . Shell 

 cavity volume of female clams was weakly correlated with number of eggs 

 produced, but number of times a female spawned was not related to number 

 of eggs produced. In the first experiment the clams were mostly smaller 

 than those used by Davis and Chanley (19 56) . The results were consistent 

 if the relationship between shell cavity volume and egg production is 

 extrapolated. In the 2nd experiment clam sizes were similar to those of 

 Davis and Chanley but number of eggs was still significantly lower. In 

 Southampton Water gametogenesis does not occur directly after spawning, 

 but in the following spring. Clams collected in January still must 

 undergo main period of gonad proliferation before spawning. Davis and 

 Chanley' s clams were from Long Island Sound where gonad proliferation 

 resumes following spawning and continues until December. For these 

 reasons, clams from Long Island Sound would be expected to produce more 

 eggs than clams from Southampton Water collected in winter. - D.L. 



Ansell, Alan D. 1968. 



Defensive adaptations to predation in the mollusca. In Proc. Symp. 

 Mollusca, Pt. II. Mar. Biol. Assn. India, Mandapam Camp: 487-512. 



This review paper states that Venus (Mercenaria) mercenaria avoids predation 

 by burrowing. The reference paper is abstracted elsewhere in this bibli- 

 ography. V. ovata and V. rhomboides can leap out of the substrate. - J.L.M. 



26 



