94 to 99.7%. Setting is about as good in Greenwich Bay despite a scarcer 

 larval population. - J.L.M. 



1044 



Landers, Warren S. 1955. 



Venus predators in Rhode Island. 5th Ann. Conf . on Clam Research, Boothbay 

 Harbor, Me. U.S. Dept. Interior, Fish Wildl. Serv.: 60-61. 



Forms definitely proven to be Venus predators are Polynices duplicata, 

 Urosalpinx cinerea, Eupleura caudata, and Neopanope texana. Suspected 

 predators are Callineetes sapidus, Limulus polyphemus , and Carcinides maenas . 

 Polynices is not a major predator. Oyster drills are serious pests, drilling 

 15% to 50% of set. Mud crabs have the potential to be the most destructive 

 because they can crush and consume very small Venus. - J.L.M. 



1045 



Landers, Warren S. 1966. 



Infestation of the hard clam, Mercenaria mercenaria , by the boring polychaete 

 worm, Polydora ciliata. Proc . Natl. Shellf. Assn. 56: 4-5 (abstract). 



Juvenile M. mercenaria were infested accidentally in laboratory trays in 

 absence of sand substrate. Experimental infestation was successful. At 

 water temps of 20 to 22°C newly hatched P. ciliata larvae metamorphosed in 

 14 to 2 days, then many settled on clams and formed tubes. Perforation of 

 the shell of 5 to 8 mm clams took 18 to 20 days, and about twice as long for 

 3 to 35 mm clams. The umbone region appeared to be especially vulnerable. 

 Internal mud blisters typical of Polydora were present 30 days after 

 perforation. Mortality was not significantly higher in infested clams. In 

 a sand substrate clams were not invaded by Polydora larvae unless they 

 failed to bury completely. When clams burrowed in, worms disappeared and 

 further shell damage ceased. P. ciliata is apparently not an enemy of clams 

 under natural conditions, but under certain conditions in a hatchery the 

 worm could be a problem. - J.L.M. 



1046 



Landers, Warren S. 1967. 



Infestation of the hard clam, Mercenaria mercenaria, by the boring polychaete 

 worm, Polydora ciliata. Proc. Natl. Shellf. Assn. (1966) 57: 63-66. 



The boring polychaete Polydora ciliata was found to attack clams raised in 

 running sea water with no burrowing substrate. In a subsequent experiment, 

 chi-square analysis showed a significant difference (at the 95% confidence 

 level) in the number of dead clams when comparing P. ciliata infested clams 

 with non-infested clams, but in later studies the differences were not 

 significant. Infestation occurred within 18 days for 5-8 mm long clams, but 

 took 39 days for clams 30-35 mm long. P. ciliata caused mud-blisters to 

 form on the clam shells. Clams that have burrowed into a substrate were not 

 susceptible to attack by P. ciliata. - D.L. 



1047 



Landers, Warren S., and Edwin W. Rhodes, Jr. 1968. 



Growth of young clams, Mercenaria mercenaria, in tanks of running sea water. 

 Proc. Natl. Shellf. Assn. 58: 5 (abstract). 



Young hard clams were placed in tanks (30' by 4 ' ) with sand and running sea- 

 water. Equal volumes of clams: 18, 13, 10, and 8 mm long, for periods of 

 30-117 days produced the growth ratios: 1.0, 1.9, 2.7, and 2.9, respectively. 

 Clams 10-18 mm long grew equally well at densities of 8 , 16, and 67 ml of 

 clams per square foot. Clams 3-18 mm long grew equally well at water flows 

 from 15-56 gpm. At 9 gpm, growth of 8-18 mm long clams decreased 33%, and 

 growth of 2-5 mm long clams decreased over 50%. Clam growth was considerably 

 better at the intake end of the tank than at the discharge end. Fouling of 

 tanks by barnacles, mussels, and tunicates reduced clam growth. Irradiating 

 water with UV light was able to control mussels only. - D.L. 



293 



