EFFECT OF CRUDE OIL POLLUTION ON OYSTERS 
147 
above the surrounding bottom and occupy but a very small percentage of the total 
acreage of those inshore waters. When the oysters reach marketable size they are 
removed from the growing areas, culled, and either shipped directly to market or 
temporarily stored in convenient protected areas near the oyster camps. It was 
during these operations that the oysters died in greatest numbers, as a result pri- 
marily of a weakened condition of the adductor muscle and its failure to maintain 
closure of the shell in air or water. During shipment the oysters opened quickly 
and spoiled because of evaporation and the loss of shell liquor, while a high per- 
centage of those transplanted to storage areas soon succumbed to the attacks of 
crabs, small fish, etc., because of their inability to close the shell. The mortality 
was greatest during the winter months and occurred on beds located at distances 
ranging from approximately one-half mile to 9 miles from the Barre oil wells and 1 to 
miles from the Pelto wells as shown in figure 1. 
During the periods from May 23 to June 1, and from August 31 to September 
2, 1933, field observations were made of the oyster mortality in Lake Barre, Lake 
Pelto, and vicinity in relation to existing hydrographical and biological conditions 
and particularly in respect to pollution of these waters by oil-well operations. These 
studies were made several months after the mortality was at its peak and after pol- 
lution of the water by oil, hydrogen sulphide, and natural gas had been considerably 
reduced by action of the Louisiana Conservation Department. 
Oil production at Lake Barre and Lake Pelto began in June and September 
1929, respectively. The most important wells are those at Lake Barre, 14 of which 
were in operation on June 1, 1933, with a production on that day of 9,987 barrels of 
oil according to a report received from the Texas Co. These wells were also pro- 
ducing at that time from 6,500 to 7,000 barrels of brine or “bleed water” daily 
which after being combined and chlorinated (since February 1933) for removal of 
hydrogen sulphide was emptied into the bay. Samples of this effluent were found 
to have a salt concentration of 123 parts per thousand as compared with 15 to 22 
per thousand for the surrounding waters. They became quite turbid soon after 
exposure to air or chlorine through the formation of colloidal suspensions of iron and 
sulphur, and gradually were covered with a thin film of oil after coalescence of finely 
divided particles. The daily output of the Lake Pelto wells was much less, amount- 
ing to only 57 barrels of oil and 650 to 750 barrels of brine, the latter having a salt 
concentration of 98 parts per thousand. 
Studies were made at 27 stations throughout this region as to the condition of 
the water and its bearing on the reproduction, growth, and mortality of oysters on 
both natural and planted beds, located in the immediate vicinity and at varying dis- 
tances from the oil wells. Particular attention was also paid to the abundance and 
activities of natural enemies of the oyster and to other marine organisms, particu- 
larly mollusks, which might be affected by oil-well pollution. 
The following observations were made in respect to the oyster-oil well situation 
in Terrebonne Parish. 
1. Random samples of oysters from planted beds in Lake Barre, Lake Pelto, 
Timbalier Bay, and vicinity, showed that a high percentage of the oysters had died 
previously on all but three of these leased areas. The mortality on the various beds 
ranged from approximately 50 to 95 percent as shown in figure 1 and in virtually 
every case included only the larger and older oysters of marketable size. Many of 
those surviving were in poor condition and exhibited retarded and abnormal shell 
growth during the preceding period. 
