employing a single dredge demonstrated a gradual though irregular decrease in the 

 number of drills caught from 3, 355 during the first hour to only 1, 858 during the 

 ninth hour . Stauber and Lehmuth (1937) suggest that it should be possible by two 

 days of work on a 10 acre bottom to reduce the hourly catch of drills by 80%. 

 Stauber (1943) later reported in more detail on controlled testing of the drill dredge 

 in Delaware Bay. During tests performed on three separate grounds in April he 

 found that the 1/2 inch mesh screen bag of an oyster dredge proved 14,5 times as 

 efficient, and the drill dredge 50 times as efficient asfhe standard wide mesh bag 

 of the oyster dredge in catching drills , He agrees with Galtsoff et al. that pro- 

 longed work on a ground with the drill dredge results in a reduction of drill catches, 

 but never in the complete removal of all drills , Stauber recommends the use of 

 the drill dredge principally during the colder months of the year when it is more 

 efficient because drills then are less firmly attached to substrata On the other 

 hand at this time of the year a large proportion of the drills may be buried in the 

 bottom and those buried in small depressions would be missed by*rhis dredge „ 

 The optimum time for dredging should be in the spring as suggested by Federighi. 



Drill box traps 



Brief mention should be made of a drill box trap which has been described 

 by Galtsoff et al . (1937) , It consists of a galvanized iron box into which drills 

 enter at the ends through special openings covered with hinged metal strips which 

 swing inward only and prevent the escape of the drills. Seed oyster bait is placed 

 in the center of the box in a small screened container . These authors indicate that 

 the chief advantage of this kind of trap is that it may be left on oyster beds for a 

 month or more untended. No mention is made of its efficiency, or how soon foul- 

 ing organisms and rusting reduce the functioning of the hinged doors . 



Federighi (1931c) made an effort to test the efficiency of a variety of 

 mollusk and fish meats as bait m attracting drills to traps in the field. Owing to 

 scavengers and putrefaction the bait did not last long enough to allow the drills 

 to react to it, even though a variety of cage types was tested. 



Drill trapping 



The drill trap consists of a bag of stout galvamzed chicken wire approx- 

 imately 12 x 15 inches in size partly filled with small bait oysters and shell which 

 give added weight and furnish substrate to help hold drills when the trap is tended. 

 These bags are attached to lines at intervals of about 8 feet on drill infested 

 ground and are tended at 5 to 7 day intervals at which time the traps are lifted, 

 shaken to dislodge the drills, examined for egg case clusters, and reset on the 

 bottom Drills, reflecting a negative geotaxis, particularly during the spawning 

 season, and an attraction to the bait, particularly if it is collected in poor growing 

 regions, climb into the traps . 



1.09 



