Stauber (1943) describes the use in Delaware Bay of a similar though stouter 

 peiforated metal plate placed horizontally under the dredge roller about four inches 

 above the deck where it receives dredged oysters; in the process of culling or fork 

 ing many drills fall through the screen and may be destroyed later . He concludes 

 that the use of the deck screen in this way has proved even more spectacular in the 

 transplantation of oysters, and in view of these results finds it difficult to under- 

 stand why this control measure has not been applied more frequently; and that if 

 methods of oyster culture in Delaware Bay are to continue along the pattern of the 

 past few decades the deck screen is a valuable adjunct to drill control. 



J. R. Nelson (1931; pers, com.) warns that hand shovelling of oysters onto 

 an inclined screen as a result of which oysters tumble over it with considerable 

 bieakage is not to be recommended because such rough handling breaks off the thin 

 bills of many of the oysters, resulting in the death of some and retardation of the 

 growth rate oi others. He adds that the horizontal deck screen as used in Delaware 

 Bay does not injure oysters appreciably. 



Drill dredge 



This method of capture utilizes a wedge shaped dredge fitted at the top with 

 an inclined screen which when dragged over drill infested oyster beds forces oysters 

 over the dredge and drills automatically fall into the dredge par.. This type of dredge 

 was invented by Captain T. Thomas in the late 19th century in the New Haven. 

 Connecticut, area, where it was considered the most piomising means of control at 

 the time (Mooie, 1898a). During the present century modified types have been 

 employed in at least Chesapeake Bay and Delaware Bay. Federighi (1931c) and 

 Galtsoff et al. (1937) give detailed drawings and descriptions of the device, Feder- 

 ighi concludes that the dredge is quite satisfactory provided the oyster population is 

 not too dense, and states that the most effective time for dredging is in the early 

 spimg when the drills have moved onto the upper layers of oysters and shell and 

 before spawning begins . 



J. R Nelson (1931) tested three different designs of dull dredges which he 

 built, but results were not sufficiently encouraging to warrant the recommendation 

 of the application of this method in Delaware Bay He fourd that the dredge racks the 

 bills of oysters, soon chokes with bottom material, and does not capture enough 

 drills to justify its use; but on beds from which oysters have been harvested and 

 which are being prepared for a subsequent planting oi for the catch of a set, as con- 

 firmed by Stauber and Lehmuth (1937), the dredge has some value. 



Galtsoff et al. (1937) corroborate J. R. Nelson's observations on the 

 inefficiency of the dredge . A test in Delaware Bay on a 15 acre oyster bottom 



108 



