No effective, practical method for barnacle 

 control has yet been developed. It was dis- 

 covered, however, that treating spat collectors 

 with DDT prevented barnacles from setting on 

 them. Dipping cultch in chlorinated benzenes 

 or the mixture commonly called Polystream 

 demonstrated that oyster spat were more 

 numerous on treated shells and barnacles 

 were virtually absent there in some instances, 

 while untreated shells were heavily covered 

 with barnacles. Treatment of cultch with Poly- 

 stream also decreases setting of certainother 

 oyster set connpetitors, including Crepidula . 



Some varieties of bottom shrimp may be 

 troublesome in covering the oyster beds with 

 mud and other nnaterials which they bring out 

 of their burrows. As yet, such conditions 

 have not been observed on our Atlantic coast, 

 but on the Pacific coast two genera of ghost 

 shrimps, Upogebia and Callianassa , cause 

 considerable damage in this way to oyster 

 grounds. These enemies now can be effectively 

 controlled by spreading over infested areas 

 dry sand or some other inactive carrier mixed 

 with chlorinated benzenes, usually Polystream, 

 and containing an insecticide, such as Sevin. 

 This method, however, has not yet been ap- 

 proved by the U.S. Public Health Service. 



Oysters, like many other sedentary bottom 

 invertebrates, are usually found with large 

 numbers of aquatic plants, including Ulva , 

 Laminaria , and Zostera . Recently, a newly 



introduced species of algae of the genus 

 Codium appeared on Sonne beds in New Eng- 

 land. Often a thick growth of these plants 

 interferes with circulation of the water, thus 

 depriving oysters of their food. When the 

 heavy growth of algae dies, it smothers the 

 oysters and, in decomposing, deprives them 

 of necessary oxygen. 



OYSTER INDUSTRY 



The United States leads all countries m the 

 quantity of oysters grown for market and in 

 value of the product. The Eastern oyster 

 represents about 80 percent of the total pro- 

 duction. At present, the Chesapeake Bay area 

 leads the sections producing Eastern oysters, 

 while the Gulf of Mexico occupies second 

 place (table 1). Several thousand men are 

 employed in various aspects of shellfisheries, 

 ranging from people who cultivate oysters to 

 those who open them and pack their meats for 

 market. 



Oyster farming has been practiced in the 

 West since the days of the Romans, and oyster 

 cultivation was practiced in China long before 

 the Christian Era. In North America, Indians 

 living near the ocean knew the value of oysters 

 and other mollusks and used them widely as 

 food. Nevertheless, farming, or, as it is often 

 called, cultivation, of oysters on the eastern 



Table 1. — Production and value of Eastern oysters - by States and areas, 1956-60 



28 



