Flame 



Large concentrations of drills frequently collect on mtertidal rocky areas 

 near drill infested bottom duiir.g the summer Their destruction by flame from 

 blow torches was started many years ago by Gibbs (pers, com ) in New England, 

 With the substitution of a flame thrower for the blow torch, the method is practiced 

 by at least one oyster grower on the east coast (J. & J. W, Elsworth Co.) and is 

 reported to be in use in various infested intertidal regions on the west coast of 

 the United States (Lindsay and McMillin, 1950). No report has been made on the 

 effectiveness of the method in reducing drill densities on the subtidal oyster 

 grounds nearest the burned intertidal areas . Such tests should be made before 

 extensive control by flame is undertaken . 



The usefulness of flame in effecting significant mortalities among drills 

 which fall directly into the water has been questioned by J. R. Nelson (pers, com.). 

 Recently R C. Nelson (1953) was able to demonstrate that under summer condi- 

 tions flaming produces mortahties of 94 to 97%. Using a total of 628 active adult 

 drills and flame from a bunsen burner and later from a blow torch, he simulated 

 controlled field operations in the laboratory. Flaming was performed on drills 

 clinging to rocks immediately removed from sea water (salinity approximately 

 30 o/oo; temperature about 22° C) and on those exposed at atmospheric conditions 

 for as lorg as 90 minutes. Flames varied m intensity from about half to full 

 strength, and were directed on individual or groups of drills until they released and 

 fell into sea water beneath, which occurred in 3 to 11 seconds . Drills flamed on 

 algal covered rocks usually drew algae between the shell and operculum and were 

 held in position, greatly increasing the mortality rate . Rate and extent of recovery 

 of burned drills was checked in the laboratory in running sea water for one to two 

 weeks. 



Electricity 



A promising field of research is presented by the response of dnlis to certam 

 electrical currents. Lindsay and his associates (1953). pioneering m this <aeld 

 (Applegate et al„, 1954), are attempting to determine whether Japanese drills 

 ( Tritocalia japomca ) can be killed, guided, repelled, or otherwise controlled by 

 electrical means Their preliminary experiments were performed m 20 x 24 inch 

 photographic trays in one inch of still sea water in the laboratory and primarily 

 with older juvenile and adult drills (20.5 to 41 2 mm. in height). The water was 

 taken directly from the laboratory sea water supply which has a normal salinity of 

 28 8 to 30 . 1 o/oo . Temperatures ranged from 12 . 5 to 14 ,0° C, and pH from 8.0 

 to 8,2 (Lindsay, pers, com.). 



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