SURVEYS 



On the first survey tripp February lO^ll^ water samples were collected 

 at 22 different stations and exajnined for salinity^ temperature, turbidity, 

 and weight of suspended solids in both surface and bottom samples o At 12 of 

 these stations where oysters exist, the population was examined for quality, 

 growth, and recent mortaiity© The oysters on all reefs were of fair quality, 

 showed up to a quarter inch new shell growth but tasted ^fresho" On three 

 of the reefs there had been a recent mortality of approximately three percento 

 This amount of mortality is usually considered negligible© The percentage of 

 market oysters on all reefs was very lowo At this time, the oysters were 

 showing the effects of fresh water since they tasted fresh, but the low 

 salinity had not lasted sufficiently long to eOAsse adverse changes o 



Since February 11, four additional surveys have been made and the 

 pertinent data with the locations of the selected stations are given on 

 the charto Stations 1 through 12 were selected for routine surveys because 

 they form north^south transects perpendicular to the flow of fresh water 

 passing through Mississippi Sound© At the present time there are no 

 significant quantities of market oysters west of the transect formed by 

 Stations 1 through 4© In the chart, salinity is expressed in parts per 

 thousand© Concentrations of less than five are considered inimical to 

 oysters© Turbidity is expressed as percentage transmission of light through 

 the sample B high readings indicate relatively clear water, and low readings 

 the reverse© 



Surveys will be continued at regular intervals so that progressive 

 changes in the area can be followed© Additional examinations are being 

 made on the suspended solids and plankton content of the water in an 

 attempt to determine their relationship to changes that are expected in the 

 oysters© 



SUMMARY 



The data collected in the past month show a progressive decrease in 

 salinity and definite but erratic increases in the amount of suspended 

 solids or turbidj-ty© By March 14 there had still been no significant 

 oyster mortality© 



The water in the entire area is now fresh enough to drink© Water 

 temperatures are sufficiently high so that oysters are physiologically 

 active© If this condition continues, we may expect a loss of the major 

 portion of the small existing population within the next two months© In 

 the first week of March, twenty=two days after the spillway was opened, the 

 Mississippi River water had still not passed through Lake Pontchartrain to 

 reach the oyster reefs in Mississippi Sound© From this fact it may be stated 

 that the fresh water in Mississippi Sound has been derived from Lake 

 Pontchartrain and from the Pearl River Basin and not from the Bonnet Carre 

 Spillway© At the present time, the Bonnet Carre Spillway is being shut down 

 and its over-flow is much less than capacity© It may be assumed, however, 

 tbAt the fresh water conditions in Mississippi Sound are going to continue 

 for some weeks to come and that an adverse environment for oysters will 

 exist there until flood stages on the Pearl River subside© 



