(1942; 1951) in trials made in English waters during dredging of oysters on muddy 

 ground demonstrated that washing of the dredge to the extent necessary to free it 

 from mud resulted in the loss of 75 to 100% of the drills.' Mistakidis (1951), also in 

 England, reports a similar experience Cole points out that the inefficiency of the 

 oyster dredge in collecting drills under three years of age is not too serious a matter 

 as at first appears, for it is probable that the quantity of egg cases oviposited by small 

 drills is insignificant in relation to that deposited by larger drills . In view of the high 

 rate of destruction of young oyster spat by immature drills, Cole's thesis does not 

 appear practical Engle (1940) confirms reports that the use of a dredge chain bag 

 with too large a mesh permits drills to escape, and adds that on the basis of the 

 rumber of egg cases diedged in this way from year to year on a given bottom, the 

 dulls do not seem to be seriously reduced in number . According to Stauber and 

 Lehmuth (1937) at least 10% of the drills collected in dredges with 1/2 inch mesh 

 bags are washed out before the dredge load is dumped on deck, all the small and 

 some of the medium sized drills being lost in this way. 



The oyster dredge with a fine mesh bag was employed as early as the 1880's 

 m Norwalk, Connecticut, to remove drills from hard bottoms, but failed to catch 

 all the drills (Goode, 1884). Fedenghi (1931c) advocated the use of a small mesh 

 bag on the oyster dredge for capturing drills, but stated that this method is effect- 

 ive only after all oysters have been harvested from drill infested oyster bottom, so 

 that all the shell, drills, and debris so removed may be disposed of. Stauber 

 (1943) notes that the 1/2 inch mesh bag holds mud easily and thus is not applicable 

 on muddy bottoms, but it may be used successfully on harder bottoms in the mannei 

 of the Long Island Sound oystermen to remove the trash, including drills, after 

 most of the oysters have been dredged. He concludes that this type of dredge is not 

 only less efficient than the drill dredge but more costly to operate . 



Deck screens 



The method of drill control involving the screening of oysters on the deck 

 of oyster boats "during transplantation and harvesting is more efficient than forking 

 (Fedenghi, 1931c; Galtsoff et al,, 1937) and is the least expensive of the drill 

 control methods but is less efficient than trapping (Stauber & Lehmuth, 1937). 

 Drill infested oysters are shovelled against a one inch mesh screen of double weight 

 chicken wire, or against an inclined or onto a horizontal perforated iron plate 

 (Stauber & Lehmuth, 1937), and drills fall through the perforations . Exposure to 

 an for a time loosens the drills and they tend to fall more readily from the oysters , 

 The inclined screen, as compared to the horizontal screen, Require s more handling 

 with forks or shovels and thus is less desirable. 



107 



