148 
BULLETIN OF THE BUREAU OF FISHERIES 
2. No evidence of unusual mortality or retarded growth was found on the beds 
at stations 23 and 24 in Lake Felicity, on 2 adjacent plantings at station 16 in 
Lake Pelto, or on a small natural oyster bed, at station 25, which is located at a 
distance of approximately 500 yards from the Barre wells. Adult oysters were also 
growing on the piling of these wells and showed a general vertical distribution ex- 
tending from 1 to 2 inches above the bottom to nearly the surface of the water. 
The shells of the latter measured from 2% to 3J4 inches and indicated continuous 
rapid growth over a preceding period of at least 1 year. 
3. The oyster beds in Lake Barre and Timbalier Bay are located at distances 
varying from approximately 500 yards to 9 miles from the numerous Barre wells. 
Those in Lake Pelto lie within a radius of from 1 to 5% miles from wells in that region. 
The previous observations failed to show any direct relation between the degree of 
oyster mortality on these beds and their distance from the oil wells. 
4. Oysters in all localities contained a considerable amount of ripe spawn. A 
heavy spawning had already occurred several weeks prior to June 1 and was still in 
progress at that time. 
5. Tow-net collections of microscopic marine life revealed an abundance of 
healthy oyster larvae as well as those of other bivalve mollusks. In the immediate 
vicinity of the oil wells the free-swimming larval stages of the oyster were plentiful 
at all ages from 1 day old to setting size. 
6. Examination of old shells and those of live oysters showed that intensive 
setting or attachment of oyster larvae had already occurred (1) on the natural beds, 
(2) on the planted beds where the mortality occurred, and (3) on the piling of the 
oil wells and other submerged objects nearby. Heavy setting was still in progress 
at the time of the investigation as shown by maximum concentrations ranging from 
200 to 500 spat per shell on those collected at the Lake Barre and Lake Pelto wells. 
7. The spat or minute seed oysters found throughout Terrebonne Parish were of 
varying ages and size, ranging from 1 day old or recently attached specimens with a 
diameter of one seventy-fifth of an inch to those 2 or 3 weeks of age having a diameter 
of approximately one-fourth to one-lialf inch. It was evident that metamorphosis of 
the oyster from the larval to spat stages had been successfully completed and that the 
growth obtained subsequently under existing conditions was rapid and to all appear- 
ances normal. No indications of unusual mortality of spat were observed. Spat 
collected at the Lake Pelto oil well at depths varying from a fraction of an inch to 
2 feet above the bottom were in good condition, as were those found on oysters in the 
test boxes at the Lake Barre oil wells and on the adjacent natural bed. Though set- 
ting and spat production is heavy throughout this region only a small percentage 
survive because of the attacks of natural enemies such as crabs and the borer {Purpura 
haemostoma). 
8. Three natural enemies of the oyster, the borer, Purpura; the boring clam, 
Martesia; and the boring sponge, Cliona, were found to be abundant on many of the 
planted beds. There was no evidence of the destruction of adult oysters by the borer. 
The shells of approximately 50 to 75 percent of the dead oysters examined showed 
heavy infestation of the boring clam and boring sponge. The numerous small tunnels 
and perforations made by these organisms had caused partial disintegration and 
weakening of the shells, interfered with normal shell growth, and, apparently, had 
been a serious drain upon the vitality of the oj^ster. Serious sponge attack and per- 
foration of the shell by the boring clam were found in many instances at the point of 
