54 OYSTER BOTTOMS OF MISSISSIPPI SOUND, ALA. 



To test the matter, apparatus and methods "- were devised for the 

 volumetric determmation of the organisms actually eaten during 

 comparable periods of tune. The result of this work, which has been 

 carried on at mtervals for several years by the author and Mr. T. E. B. 

 Pope, has shown that while the quantity of water filtered is great, 

 averagmg, roughly, about 30 quarts daily for oysters 4^ mches long, 

 the volume of tlie livmg food is insufficient to account for the actual 

 growth of the oyster, makmg no allowance for the requirements of 

 the other vital activities. It appears that finely divided organic 

 debris or detritus, which constitutes the major part of the material 

 mgested, plays a more important role in the oyster diet than has been 

 conceded, a view which recently has been advanced by Petersen and 

 Jensen.'' 



In view of these facts and probabilities, and the present impossi- 

 bility of establishing a standard for the expression of the quantity of 

 food available, the data respecting the food content of the water col- 

 lected during this survey will not be stated here. A special paper on 

 the entire subject of the food and feeding of oysters will be issued 

 on the completion of the studies. 



It may be stated from observation of the oysters and on general 

 grounds that the food supply in Mississippi Sound and minor con- 

 tiguous waters is ample. 



OYSTER ENEMIES. 



The survey, smce it was carried on during the colder season of the 

 year, was not favorably timed for the study of the enemies of the 

 oyster in this region. The only ones observed were a few drills and 

 mussels, but the drumfish also is known to occur. 



Drill, horer, snail, whelk, conch, etc. {Purpura hsemostoma) . — A com- 

 paratively small number of the animals variously known by these sev- 

 eral names was found on the natural oyster beds, particularly those in 

 the vicinity of Little Dauphin Island from Pass aux Herons south- 

 ward. This is the region nearer the mouth of Mobile Bay, and there- 

 fore the more accessible to the influx of salt water from the open Gulf. 



On some of these beds the drills were found at their work of destruc- 

 tion but m other places their presence at tmies was to be inferred only 

 by the mortality, especially among the spat and young oysters, which 

 are more susceptible than adult oysters to their attacks. 



It can not be stated that these enemies were particularly destruc- 

 tive at the tune of the survey, but it is reported that many oysters 

 have been destroyed by them at intervals in the past, and, as might be 



a Volumetric studies of the food and feeding of oysters. By H. F Moore. (Proceedings of the Fourth 

 International Fishery Congress, Washington, 190S.) Bulletin Biueau of Fisheries, vol. xxvni, 1908, 

 p. 1295-1308. 



b Valuation of the Sea. I.— Animal life of the sea bottom, its food and quantity. By C. G. Joh. 

 Petersen and P. Boysen Jensen. Report of the Danish Biological Station, xx. Copenhagen, 1911. 



