Figure 15. — Group of starfish feeding on oysters. Note rwo empty shells in upper left comer with meats already eaten. 



found together with transplanted oysters but 

 also boring sponges, tunicates, hydroids, 

 Crepidula , and worms. One minute of immer- 

 sion, especially if the starfish are kept on 

 deck for a short time before being returned 

 to sea water, kills them all regardless of size. 



Recently, biologists have been experiment- 

 ing with certain orgaiuc chemicals mixed with 

 dry sand or sonne other inert carrier and then 

 spread on bottoms infested ■with starfish. 

 Under experimental conditions some of the 

 formulas appeared effective. This approach 

 is being further developed and evaluated. 



Several species of flatworms kill oysters, 

 especially young ones. On the Atlantic coast 

 two species of Stylochus , S^. ellipticus and 

 S. inimicus , comnrionly called oyster leech, 

 cause heavy losses. These predators, meas- 

 uring from 1/ 2 to 3/4 inch, crawl inside the 

 oyster shell and feed gradually on its meat 

 until they kill the host. According to observa- 

 tions made in the 1930's, these flatworms 

 were extremely destructive in Appalachicola 

 Bay, Fla., and other southern localities. Re- 

 cently, many have been found in several areas 

 of Long Island Sound and in isolated salt- 

 water ponds in Martha's Vineyard, Mass. 



Dipping dredgeloads of oysters in a saturated 

 salt solution will kill these worms. 



Almost aill crabs with claws large and strong 

 enough are oyster killers. In Long Island 

 Sound, the rock crab. Cancer irroratus ; green 

 crab, Carcinides maer.as : blue crab, Calli- 

 nectes sapidus : several species of mud crabs 

 belonging to the genus Neopanopeus : and other 

 groups feed upon oysters, especially young 

 ones with thin, brittle shells. In southern 

 waters the stone crab, Menippe mercenaria , 

 is abundant and destroys many oysters. 



A crab usually holds an oyster in its claws 

 and cracks off the shell piece by piece. Young 

 oysters from a fraction of an inch to an inch 

 or so in size are especially easy prey. Crabs 

 are quite destructive. For exaimple, one stone 

 crab 3 inches wdde was caged for 9 weeks with 

 oysters from 2-2 1/2 inches long. During this 

 period it killed 237 oysters, an average of 26 

 per week. The maximum number killed in a 

 single week was 60, 



Crabs can be controlled by several methods. 

 Properly constructed wire fences surrounding 

 oyster beds are an effective protection agsiinst 

 crabs that cannot swim. Trapping crabs to 

 reduce their numbers is another method. 



23 



