OYSTER BOTTOMS OP MISSISSIPPI SOUND, ALA. 53 



It will be observed that the readings in Mississippi Sound, includ- 

 ing those on the beds near Grants Pass, cover the period from Novem- 

 ber 24, 1910, to April 9, 1911, with an intermission from January 17 

 to March 13. During this period the average specific gravity varied 

 with time and place between 1.0150 and 1.0235 as compared with 

 fresh water as 1.0000 and full ocean water between about 1.0250 and 

 1.0260. The lowest specific gravity observed during this period was 

 1.0114 near Pass des Huitres on January 25 and the highest was 

 1.0247 off Mid Signal early in December. 



The maximum specific gravities are probably as high as usually 

 occur in this region, but in times of freshet in neighboring streams 

 the water undoubtedly becomes much fresher than was observed dur- 

 ing the survey. In February and March, 1894, when the previous 

 reconnoissance was made, the water at the bottom of the east end of 

 Grants Pass was 1.0028, at the north end of Portersville Bay 1.0036, 

 about 1 mile southeast of Point aux Herbs 1.0063, and in the mouth 

 of Heron Bay 1 .0000 or absolutely fresh, in all cases being much lower 

 in salinity than at the corresponding season of 1911. 



These low salinities are all of them below that which is desirable 

 for the production of the best oysters, and the lowest, if it long pre- 

 vailed, would prove fatal. It is apparent, however, that these con- 

 ditions are but occasional and that normally they do little or no harm. 

 It is probable even that they are beneficial in periodically reducing 

 the saltness of the water below that which can be tolerated by the 

 drill or borer and by that means keeping that destructive enemy from 

 becoming so numerous as to menace the beds. 



OYSTER FOOD. 



In reports on previous surveys a feature usually has been made of 

 the subject of the quantity of oyster food carried by the waters. 

 These discussions have been confined practically to diatoms, minute 

 microscopic plants, which authors generally have been prone to regard 

 as supplying practically all of the oyster's nutriment. Volumetric 

 studies of the microorganism content of the water begun in connec- 

 tion with the survey of Matagorda Bay ^ in 1905 revealed a quantity 

 so small as to excite the author's suspicion that the livmg matter was 

 of less relative importance than had been generally supposed. 



It appeared possible, however, that the quantity of water filtered 

 by the oyster might be greater than generally supposed and digestion 

 more rapid, and that despite appearances the small quantity of micro- 

 scopic living organisms in the water and present in the stomach at 

 any one time might be sufficient to furnish material for the growth and 

 general physiological activities of a sluggish animal like the oyster. 



a Survey of Oyster Bottx)ins in Matagorda Bay, Tex. By H. F. Moore. Bureau of Fisheries Docu- 

 ment No. 610. 



