for very long, oysters do not thrive. For short periods of time, 

 ten days perhaps in warm ?;ater, they roay exist in entirely fresh 

 water without untoward aftereffects. The actual length of time 

 that the oyster can survive will depend on the temperature and the 

 amount of stored food in its tissues. If the temperature of the 

 water is low, as in winter, it may survive many weeks. Experi- 

 mentally, they will survive several months when kept in a refriger- 

 ator. However, if temperatures are high, exposure to fresh water 

 for only a few days may be detrimental. 



For these reasons, a study of the salinity levels in Mississippi 

 Sound and Lake Mechant over a long period of time helps to evaluate 

 these areas in terms of possible oyster production. 



During the past six months, salinity determinations were made 

 at the various stations in Mississippi Sound and Lake Mechant to 

 observe the effects of the annual spring floods in these areas. 

 The data have particular interest in view of the widespread 

 mortality which occurred this past spring, Mississippi Soimd is 

 in the shape of a long narrow and shallow basin; because of these 

 physical features, the effect of wind is great on water movement 

 and as a consequence on the salinity. Continued winds from the 

 north and northwest have the tendency to keep out the more saline 

 waters of the Gulf of Mexico. South and southeast winds tend to 

 increase the movement of Gulf water into the Sound. In the same 

 manner, the ebb tide allows the fresh river water to enter the 

 Sound and the flood tide brings into the Sound water having a 

 higher salt content. 



The difficulties involved in maintaining continuous records 

 of salinity are too great, so advantage was taken of the water 

 movement to insure the collection of water samples when salinity 

 levels would be at or near the maxima. All of the following data 

 were obtained when the wind movement was either negligible or from 

 the south and southeast. The stage of the tide varied from one 

 quarter to full flood. This means that on the dates indicated, 

 the greatest salinity for the day has been recorded. By spot 

 sampling, it was found that in between the several surveys the 

 salinity levels were both higher and lower. 



The average salinities compiled from the data for the 

 period are consistent with the poor condition and high mortality 

 of the oysters in this area. Table 5 shows the range in bottom 

 salinities at a series of stations extending roughly north-south 

 across the west end of Mississippi Sound in Area II, These samples 

 were collected over a 4-hour period while the tide varied between 

 half flood and high water. 



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