recorded on a kymograph to check their feeding activity. In a parallel study 

 the immersed weight of 50 other oysters under various conditions was followed 

 as an index of growth. 



The data obtained by the kymograph recordings for one of these oys- 

 ters (about 4 inches long) are presented in the figure. The three highest peaks 

 of water pumping and shell opening were associated with the addition of some 

 fresh sea water to the system, A fourth peak of activity, especially shell open- 

 ing, occurred from May 15 through May 17, Since the daily log book of the 

 sea-water laboratory gives no indication of either fresh sea-water additions 

 or other changes, we are unable to suggest any possible causes for this peak. 



Daily record of number of 

 hours open and volume of 

 water pumped by aJi oyster 

 maintained in sea- water 

 laboratory. Because of 

 failure in the experimental 

 set-up no record of volume 

 of water pumped was ob- 

 tained on May 17, 18, and 

 19. Arrows indicate the 

 dates that some fresh sea 

 water was added to the 

 system. 



The volume of feces deposited by the two oysters used in our experi- 

 ments was roughly proportional to the amount of water pumped. There are, 

 however, indications that feces deposition per volume of water filtered de- 

 creases as the sea water ages. Such a decrease is to be expected since the 

 water passes through a sand and gravel filter bed each time it is recycled. 



A maximum pumping rate of about 20 liters per hour was obtained 

 during these studies. The volume of water pumped during the first 2 or 3 days 

 following the addition of fresh sea water was comparable to that observed for 

 oysters of similar size in running sea water at Pensacola, Florida. Our pre- 

 liminary studies indicate that frequent additions of fresh sea water will prob- 

 ably be necessary for the long-time maintenance of oysters in this system. 

 If the reduction of the oyster feeding activity associated with the aging of the 

 water is due solely to a diminution of the food supply, the problem may be 

 solved by artificial feeding. 



73 



