and other invertebrates were killed. On treated 

 beds where current velocities were between 0.9 and 

 2.7 km. per hour, treatments killed only small per- 

 centages of fish, small clams, crabs, and other 

 invei-tebrates. A few hours after the treatment the 

 area appeared to be nontoxic to these animals. 



5. A higher percentage of oyster drills was 

 killed by treatments made in late April and early 

 May than later in the summer. 



6. Oyster drills were killed by the toxic action 

 of Polystream, not by fish or crabs after they be- 

 came swollen. In a small number of instances, how- 

 ever, they were consumed by starfish. 



7. Oyster drills that survived a treatment ap- 

 peared to be affected by the treatment to the extent 

 that they did not feed significantly for a few 

 months and, thus, did not kill many oysters. 



8. The number of oyster drills on a bed where 

 seed oysters were planted and removed each year 

 remained low for at least 2 years. 



9. Oyster drills killed less than 2 percent of 

 young oysters during the first year on most treated 

 beds. 



10. Growth of oysters appeared to be normal on 

 treated beds. For example, on one bed 1-year-old 

 oysters increased in volume from less than 1 cc. 

 to 1,5 cc. in one growing season. 



ACKNOWLEDGMENTS 



Barry Baiardi, Russell Clark, Otis C. Lane, 

 John J. Manzi, and Nicholas Penchuck provided 

 technical assistance. Hillard Bloom and the Bloom 

 Brothers Oyster Company; J. Richards Nelson 



and the former F. Mansfield and Sons Oyster 

 Company; Lester Johnson and G. Vanderborgh, 

 Jr., of G. Vanderborgh and Sons Oyster Com- 

 pany; and Arnold Carr, Division of Marine Fish- 

 eries, Mass., also helped me. 



LITERATURE CITED 



Haven, Dexteb, Michael Castagna, Paul Chanley, 

 Mabvin Wasb, and James Whitcomd. 



1966. Effects of the treatment of an oyster bed with 

 Polystream and Sevin. Chesapeake Sci. 7 : 179-188. 

 LoosANOFP, Victor L. 



1960. Some effects of pesticides on marine arthro- 

 pods and mollusks. Biological problems in water 

 pollution. In Transactions of the 1959 Seminar, 

 pp. 89-93. U.S. Dep. Health Educ. Welf., Public 

 Health Serv. 



1961. Recent advances in the control of shellfish 

 predators and competitors. Proc. Gulf Carib. Fish. 

 Inst, 13th Annu. Sess., pp. 113-127. 



LoosANOFP, V. L., C. L. Mackenzie, Jr., and L. W. 

 Shearer. 

 1960a. Use of chemicals to control shellfish pred- 

 ators. Science (Wash.) 131: 1522-1523. 

 1960b. Use of chemical barriers to protect shellfish 

 beds from predators. Fish., Wash. State Dep. Fish. 

 3 : 86-90. 

 Schwartz, N., H. E. Gaffney, M. S. Schmutzer, and 

 F. D. Stefano. 

 1963. A method for the analysis of chlorinated ben- 

 zenes in clams (^[ercrnaria mcrcenaria) and oys- 

 ters {Crassostrea vh-ginica). J. Ass. Off. Agr. 

 Chem. 46 : 893-898. 

 Wood, Langley, and Beverly A. Roberts. 



1963. Differentiation of effects of two pesticides upon 

 Vrosalpinx cinerea Say from the Eastern Shore of 

 Virginia. Proo. Nat. Shellfish. Ass. 54: 75-85. 



CONTROL OF OYSTER DRILLS WITH POLYSTREAM 



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