Cole (1951) believes that intensive dredging of heavily infested oyster 

 ground during the period between spawning and hatching of drills will always be 

 an important measure of control. At this time a very high proportion of females 

 is collected by the dredge (Cole, 1941), possibly because the male is more easily 

 detached from the cultch than the female In addition egg cases which are usually 

 deposited on objects large enough to be retained by the dredge are removed. T. C. 

 Nelson (pers com.) logicaJly rebuts that the intensive dredging advocated by Cole 

 would remove much of the new growth on the oysters, thus prolonging by one or more 

 years the time required to market the crop, and subjecting the oysters to a longer 

 period of attack by drills 



Production of oysters in the United States according to Glancy (1953) will 

 never increase substantially until effective methods of drill control are universally 

 established. 



At this time no single panacea for the control of theNjxill is available. It is 

 certain, though, that control must necessarily involve a number of cooperative, 

 continuous, long range operations over a large area The nature of the control 

 may well have to vary from region to region commensurate with the depth of the 

 water, the nature of the bottom, and the resources of those charged with the direc- 

 tion of the control operations A critical review of all known methods of control 

 which have been attempted is given in the following sections. 



Capture of Drills and Egg Cases 

 Hand picking 



The gathering of drills by hand in the intertidal zone at low water has been 

 recommended by Cole (1942), Adams (1947), and Cahn (1950) as an effective means 

 of control. Cole writes that on some beaches along the River Blackwater system in 

 England one man can collect 500 drills in a few hours, and concludes that the de- 

 tachment of men from normal dredging operations for the work of hand picking is 

 justified, Adams advises that best results are obtained by picking early in the 

 spring before egg cases are deposited, Cahn describes a novel program for drill 

 eradication by hand picking in Japan where, to remove Japanese drills from inter- 

 tidal oyster collectors, the prefectures of Hiroshima and Miyagi established an 

 oyster drill extermination day at which time the school children swarm over fh.e 

 oyster beds at low tide and gather all the drills they can find. 



T C. Nelson (pers. com ) considers that hand picking of drills is theoret- 

 ically sound, but is not as effective in actual practice as would be desired. On a 

 recent trip to England, in company with Mistakidis and associates, he attempted 

 hand picking drills on the intertidal flats of the River Roach , Even with utmost 



105 



