planted with young oysters was divided into four equal parts, and one of the 

 quarters was intensively drill trapped When the oysters were harvested the 

 quarter which had been trapped yielded appreciably more oysters than the other 

 three quarters combined In the final report on his investigations, Stauber (1943) 

 recommends the zigzag arrangement of trap lines, with the trap lines placed 

 parallel to the flow of the tidal current and left in place for a season . Placing 

 the trap lines across the current did not increase drill catches and greatly increased 

 operating difficulties. He lecommends the use of unculled rank inexpensive brack- 

 ish water or creek oysters, which are usually well covered with attached barnacles 

 and ribbed mussels, as drill trap bait. In utilizing bait from poorer growing 

 habitats Stauber was the first to employ bait which Haskm's (1940 : 1950) studies 

 demonstrated is most effective in attracting drills in the more favorable oyster 

 growing areas. Stauber also recommends rebaiting the traps four times during a 

 trapping season in Delaware Bay. This may extend over that part of the year in 

 which water temperatures above 10 °C and salinities above 15 o/oo occur (approxim- 

 ately April to October inclusively) . Stauber concludes that total removal of oyster 

 drills by means of the drill trapping method alone is not possible unless huge sums 

 of money are expended, but that "what can be accomplished is that the density of 

 these pests can be reduced to such a level that oystering will become consistently 

 more profitable" . One defect of the drill trap developed in Delaware Bay is its lack 

 of a find screen bottom which would retain drills as the traps are raised through 

 deep water and in rough weather (T. C. Nelson, pers. com.). 



Newcombe et al. (1941-42) guided by the work of Stauber carried out some 

 preliminary drill trapping studies in the York River area, Virginia, during the 

 summer of 1942, but report no new information. At first Cole (1942) strongly 

 recommended the use of drill traps in English waters since the spawning habits of 

 English drills are the same as those in America; but later he (1951) reversed his 

 opinion, stating that drill traps are not effective . In a personal communication he 

 writes that his group is using other types of "Trap^" siccessfully, but that the 

 standard pattern described by Galtsoff et al. (1937) is not apparently suited to British 

 conditions. He does not describe the types employed Despite the fact that drill 

 trapping appears feasible from an economic point of view (Stauber & Lehmuth, 1937) 

 and that it can be superior to other methods of control in reducing young drill con- 

 centrations, there has been no widespread adoption of the method for the control 

 of the oyster drill (Glare y, 1953). T. C. Nelson (pers, com.) adds the clarifying 

 note that the failure of those oyster growers, who have attempted drill control by 

 meai.s of drill trapping, to attempt cost accounting, their aversion to extra work, 

 and their tendency to gamble are chief factors in the failure of drill trapping to date . 



Ill 



