care many oysters were pushed into the mud by their feet, raising the question 

 whether such damage to oysters might not have equalled that which the collected 

 drills would have inflicted. Nelson observes that on hard bottoms hand picking is 

 more feasible, but since drills on exposed flats crawl under objects, careful hand 

 picking would involve turning over every oyster and shell which lies sufficiently 

 free of the bottom to permit drills to. lodge underneath. He concludes that the drill 

 nap offers the best known means for drill control in intertidal areas: it provides 

 attractive food, cover from the sun, more favorable location for oviposition, and 

 is easily tended . 



So far as the writer knows the quantitative effectiveness of eradicating a 

 small proportion of a drill population by such locabzed measures as hand picking, 

 and by a number of other methods to be described, has never been tested. Such 



rol measures probably bring only short term localized relief from predation. 

 Although not verified experimentally in the case of drill populations, knowledge of 

 other motile animal populations suggests that the extermination of a peripheral 

 portion of a large population merely reduces the overall density and consequently 

 inter- and intraspecies competition, with the result that the residual population soon 

 resumes its former magnitude. Controlled tests should be effected before local- 

 ized eradication measures on a costly and large scale basis are inaugurated, 



Forks 



The use of forks to shake drills from oysters on the deck of oyster boats 

 :s suggested by J. R Nelson (1931), Fedenghi (1931c), and Galtsoff et al (1937) 

 as a simpie and inexpensive method They also recommend that oysters be thrown 

 overboard with forks instead of shovels sofhat drills present may pass through the 

 tines o<i:o ihe deck to be destroyed later , J R Nelson adds, however, that the 

 [lumber of drills so recovered is not large . 



Concrete pillars 



The use of small concrete pillars onto which drills will crawl has been 

 suggested by Fedenghi (193 ic) as a means of trapping, J R Nelson (1931) observes 

 that the s< pillars will not collect drills as effectively as the drill trap, they expose a 

 limited surface cirea, are heavy and difficult to handle in moderately deep water 

 and in strong tidal currents. No field tests have been reported on this method; on 

 the whole, it aopears quite impractical. 



Oyster dredges 



The conventional oyster dredge (J. R. Nelson, 1927) with the large mesh bag 

 ?; quite inefficient for drill control. The greatest advantage is probably secured by 

 the removal of shells and oysters bearing drill egg cases (Glancy, 1953) . Cole 



106 





