In Table 2 is a summary of the mortality that was found on the 

 natural oyster bars when the trays were placed in position together 

 with the mortalities that occurred during the foxir months of observa- 

 tion either in the trays or on the reef. One of the trays was lost 

 and replaced; two other were lost during the final month. On some 

 of the survey trips it was too rough to get the cages out of the 

 water. When it wes not possible to obtain the mortality rate from 

 the samples of oysters in the trays, oysters were dredged from the 

 natural reef. Only clean shells remaining hinged together were 

 included in computing the mortality rates on the reef oysters. The 

 final figiires in the table show the total estL-uated mortality which 

 occurred at each station dui'ing the period from December, 1948 to 

 June, 1949, The samples in the cages were not large and in some 

 locations it was not possible to find enough oysters to consider 

 the sampling adequate. With these reservations in mind, the mor- 

 tality figures provide a fair index of the conditions at the stations 

 during the first half of 1949. 



Stations 12 and 13, having the highest indices of mortality, are 

 also the two locations lying in closest proximity to the sources of 

 fresh water for this end of Mississippi Sound. The mouth of the 

 Pearl River is only four miles west of Station No. 13. Stations 17, 

 18 and 19 are located from 5 to 12 miles east of the Pearl River, 

 The mortality rates at these locations were approximately equal and 

 resulted in the loss of half of the meager oyster population still 

 present. 



The size of the oysters dying was not restricted to aivy par- 

 ticular group. When the survivors were measured the distribution 

 of size groups followed a normal distribution curve indicating that 

 larger oysters succumbed as readily as the smedler ones. 



Oysters from Station 17 which had been transplanted to Florida 

 and observed during the period February to June, showed a total 

 mortality for the five months of 17 per cent. This rate while only 

 one-third that of Station 17 is still abnormally high. The death 

 of most of these was found, however, to be due to the depredations 

 of mud crabs. Examination showed that the mortality of these oysters 

 at Florida, aside from external predators, was approzimately 5 per 

 cent, which is within the accepted range. 



At Lake Mechant the condition of the caged oysters was strikingly 

 different. The average death rate was less than 2 per 100 oysters and 

 at least one of the deaths was Imown to be accidental. This mortality 

 rate is less than what might be expected on a normal oyster bar for a 

 four months period. At Station 20 and 22 the bottom was so soft that 

 the trays of oysters sank into the mud and sand to a depth of six inches. 



11 



