Figure 14. — Common starfish, Asterias forbesi . one of the most important enemies of oysters in Long Island Sound 



and other areas of the Atlantic coast. 



very small and cannot take in large pieces of 

 food. To overcome this difficulty, the starfish 

 has developed an unique method of feeding. 

 After the oyster shells are opened, the star- 

 fish extrudes its stomach and inserts it 

 between the shells, digesting the soft oyster 

 meat. As soon as the moUusk is eaten, the 

 starfish withdraws its stomach with a set of 

 retractor muscles. The starfish is very de- 

 structive, and a medium-sized individual may 

 destroy up to seven 1-year-old oysters in a 

 day (fig. 15). Older and stronger oysters are 

 better equipped to withstand a starfish attack, 

 but even a large oyster, if weak, may become 

 easy prey to starfish. 



Starfish eradication has been practiced since 

 oyster cultivation began. Various methods are 

 used now. Among mechanical approaches, star- 

 fish mops (figs. 16 and 17), oyster dredges 

 (fig. 18), and suction dredges are used to re- 

 move starfish from the bottonn. Recently, 

 Bureau biologists demonstrated that several 

 oyster enemies, including drills and starfish, 

 may be destroyed by being buried under a 

 comparatively thin layer of bottom mud. At 

 present, special underwater plows are being 



used in experiments to develop a practical 

 model to operate on comnnercial oyster beds. 



Since mechanical methods of starfish control 

 are quite expensive and only partially effec- 

 tive, biologists have experimented with chemi - 

 cals to find those that may be practical for 

 exterminating these predators. Good results 

 were obtained with quicklime (calcium oxide). 

 When quicklime is spread over the oyster beds, 

 its falling particles imbed in the upper sur- 

 faces of the starfish body, which is covered 

 with a delicate membrane acting as a respira- 

 tory organ. The caustic action of the lime 

 causes surface lesions which sometimes 

 quickly deepen and, after a few days, penetrate 

 through the starfish body and kill it. Although 

 many lightly injured starfish recover, the 

 method still is quite effective if used properly. 



An extremely simple method of killing star- 

 fish during transplanting of oysters from one 

 bed to another, developed at Bureau of Com- 

 mercial Fisheries Laboratory, Milford, Conn., 

 consists of dipping dredgeloads containing 

 oysters and other bottom material in a satu- 

 rated or strong solution of common salt. This 

 method is effective in killing not only starfish 



22 



