CONTROL OF OYSTER DRILLS, EUPLEURA CAUDATA AND 

 UROSALPINX CINEREA, WITH THE CHEMICAL POLYSTREAM 



BY CLYDE L. MACKENZIE, JR., FISHERY BIOLOGIST 



BUREAU OF COMMERCIAL FISHERIES BIOLOGICAL LABORATORY 

 MILFORD, CONN. 06460 



ABSTRACT 



Five experimental and 10 commercial treatments of 

 oyster beds In four States were made with Polystream. 

 On a typical bed, where water currents were less 

 than 2.7 km. per hour, Polystream killed about 85 

 percent of the thick-lipped drill, Eupleura caudata, 

 and 66 percent of the Atlantic oyster drill, Vrosalpinx 

 cinerea. A significantly higher percentage of oyster 

 drills was killed by treatments made in late April and 

 early May rather than later in the summer. Oyster 



drills that survived did not feed for several months. 

 The number of drills remained low for at least 2 years. 

 Polystream treatments killed only small percentages of 

 fish, small clams, Mercenaria mercenaria, crabs, and 

 other Invertebrates. After a treatment, oysters, Crassos- 

 trea virginica, clams, and other organisms had small 

 residues of Polystream In their tissues but gradually 

 lost these residues. Growth of oysters was normal on 

 treated beds. 



Boring gastropods, known as oyster drills, and 

 starfish, Asterias forhesi, are the most, serious pred- 

 ators of oysters in Long Island Sound. The drills 

 prey heavily on oysters, Crassostrea virginica, 

 along the entire Atlantic Coast, from Canada to 

 Florida, and in certain areas of the Pacific Coast. 

 Where they are extremely numerous, oyster drills 

 destroy nearly all oysters on commercial beds. In 

 Long Island Sound, however, drills usually reduce 

 the number of oysters to such a level that most 

 beds are of marginal value commercially. 



This article summarizes laboratory and field 

 experiments made during the development of a 

 control method of oyster drills for use on com- 

 mercial oyster beds in southern New England and 

 New York; it includes the results of ,15 treatments 

 during 1961-67. 



HISTORY OF DEVELOPMENT OF METHOD 



All early phases of work on the development 

 of a method of control of oyster drills by use of 

 Polystream, including the initial testing of chem- 

 icals, was done by the biological laboratory at 

 Milford, Conn. Field tests and commercial appli- 

 cations of Polystream were made under the 

 inspection of the author in the States of Connecti- 

 cut, New York, Rhode Island, and Massachusetts. 

 Additional independent laboratory and field stud- 

 ies were later made in Virginia. 



Published May 1970. 



FISHERY BULLETIN: VOL. 68, NO. 2 



EXPERIMENTAL WORK AT MILFORD 



In 1946, the Fish and Wildlife Sfervice biologi- 

 cal laboratory, Milford, Conn., began a program 

 of screening organic chemicals with the goal of 

 eventually developing a method to control oyster 

 drills (Loosanoff, 1960). A method was sought 

 that would kill oyster drills, but would not harm 

 oysters, clams, Mercenaria mercenaria, and other 

 organisms on a shellfish bed, and also would not 

 leave residues in tissues of shellfish that would be 

 harmful to man. Tests were made in the laboratory 

 and the field. 



Laboratory Tests 



Loosanoff, MacKenzie, and Shearer (1960a, 

 1960b) reported that chlorinated benzenes, such as 

 monochlorobenzene, orthodichlorobenzene, para- 

 dichlorobenzene, trichlorobenzene, tetrachloro- 

 benzene, and their mixtures, are toxic to several 

 species of marine gastropods, including the thick- 

 lipped drill, Eupleura caudata, and the Atlantic 

 oyster drill, Urosalpinx cinerea. These chemicals 

 were- selected for further tests because they were 

 toxic to snails, virtually insoluble in sea water, 

 and of sufficient density to settle to the bottom of 

 the Sound. The last two characteristics reduced 

 the chance of damage to any but bottom-dwelling 

 organisms whose soft parts contact the chemicals 

 directly. Small quantities of Sevin (1-naphthyl- 



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