EFFECT OF CRUDE OIL POLLUTION ON OYSTERS 
151 
water level is largely determined by the direction and velocity of the wind. Northerly 
winds drive the water out, while southerly winds pile it up inside. In either case the 
difference caused by wind may exceed 1 foot under ordinary conditions and as much 
as 10 feet during a hurricane. Since the land elevation above mean liigh water 
seldom exceeds 2 feet, it is evident that even moderate winds result in considerable 
wash from the marshes. 
On many of the beds the oysters were found to be quite variable in fatness. In 
general, it appears that accumulation of glycogen occurred very late during the winter 
of 1933-34. Many oystermen stated that their oysters were in better condition dur- 
ing the latter part of March than at any time previously in the season. It is possible 
that the customary planting level of 600 to 800 barrels (1,500 to 2,000 bushels) per 
acre is excessive at times for the amount of food available. 
Two previous surveys of the area made, by Moore in 1898 (1899) and by Moore 
and Pope from 1906 to 1909 (1910), were not sufficiently detailed to permit direct 
comparison of hydrographic data. However, it seems safe to say that except for 
the elimination of extraordinary fluctuations in density resulting from crevasses, the 
salinity observed in 1934 appears to be much the same as during the 1909 survey. 
In 1898 the water in Terrebonne Bay was found to be fresher than in Timbalier 
Bay, an observation not borne out by our determinations, as the salinity now is 
approximately the same in both bays. It is said that owing to the freshness of the 
water no oysters were found in Terrebonne Bayou above Lake Lagraisse prior to 1883. 
It was also stated in 1898 that considerable changes in topography were occurring in 
Terrebonne Bay. Such changes consisted in the tearing down of large amounts of 
marsh land then present in Terrebonne and Timbalier Bays, and separating Terre- 
bonne Bay from Lake Barre. It was at one time possible to go from Houma to Tim- 
balier Island by land. Undoubtedly this continued destruction of land area has been 
one of the most important factors bearing on oyster culture in the region, for the 
absence of obstructing land permits the rapid mixing of Gulf water with the fresh 
water from the bayous and serves to maintain a relatively high salinity (16 parts per 
million, February 1934) to the upper parts of Lake Barre and Lake Felicity. 
At the time of the 1898 survey market oysters were no longer produced in Bara- 
taria Bay, which includes Lake Washington (Grand Ecaille), and only a few dead 
reefs existed there as evidence of previous importance. The chief oyster-producing 
region was Terrebonne Bay, which included Lake Pelto. Since then the beds in 
Barataria Bay have been rehabilitated and extended so that at present some of the 
finest oysters are produced here. Although Terrebonne Parish still is foremost in 
quantity, the quality is in general inferior to Barataria Bay. 
Insofar as shape, growth, and quality are concerned, observations just made are 
in almost complete agreement with the early survey, and such discrepancies as exist 
may be caused in part by confusion in identifying localities from the local names in 
use at that time. 
An effort was made to obtain a definite record of sudden and unexplained losses 
of oysters in the past. No such occurrences were found other than the occasional 
killing of oysters said to have been caused by freshets due to breaks in the levee. 
