SPAWNING AND SETTING OF OYSTERS 
81 
at different places and during different periods of time. The heaviest set was obtained 
at the Deer Islands in August when the inside surfaces of the shells in each bag (one- 
half bushel) bore nearly 20,000 spat. The outer surfaces of the shells probably 
received as heavy a set, so it may be said that the set amounted to 40,000 spat per half- 
bushel bag of shells. In Figure 17 is a photograph of a clump of shells from one of 
these bags showing the great abundance of young spat. 
In some cases the spat are too abundant for they would tend to grow into coon 
oysters unless broken apart while still relatively small. If left in the water longer 
even more would set on the same shells, resulting in considerable crowding. Shells 
which are merely spread on a reef as cultch can not readily be removed when the 
proper amount of set is obtained, but the bags may be removed when desired and 
transferred to beds in deeper water for growth where little or no further setting occurs. 
Also, after the shells in bags have become slimy and bear no set, the bags may easily 
be taken up and left in the sunshine for a few days, and then put back into the water 
as clean cultch on which larvae will set. In this manner seed may be collected in 
desired abundance for planting on private grounds or for developing new public 
grounds. 
Table 3. — Number of spat on the inside surfaces of shells planted in Galveston Bay, 1929 
Date 
planted 
Date 
removed 
Place 
Spat per 
half 
bushel of 
shells 
Date 
planted 
Date 
removed 
Place 
Spat per 
half 
bushel of 
shells 
AT ay 6 
May 20 
Bayou, main reef 
975 
June 25 
July 10 
Bayou, middle ground.. 
Deer Island 
67 
2,700 
1,800 
15. 000 
19. 000 
(>) 
Apr 18 
May 23 
Hanna reef 
212 
Do 
July 18 
May 20 
May 28..-. 
May 31 
.Turin 25 
May 31 
Bayou, middle ground.. 
Bayou, main reef 
120 
July 15 
Aug. 6 
Hanna Beef .. 
June 25 
31 
Aug. 3 
Aug. 14 
Deer Island 
do 
Deer Island. 
22 
Do 
Aug. 22 
_do 
July 9__ 
1, 270 
Aug. 20 
Aug. 27 
Bayou, main reef 
1 Spat present, but not counted. 
This method may be employed as an economical means of developing oyster 
ground in places not near the natural reefs. The removal of common coon oysters 
from reefs as seed is also advisable but this method involves more labor in culling 
and transportation than that above described. More recently the use of cement- 
coated egg-crate partitions (Prytherch, 1930) has been found to be highly efficient as 
a method of collecting seed oysters. This method might well be employed on the 
Texas coast. Such modern methods of oyster culture if applied extensively in the 
coast waters of Texas should increase the production of oysters tremendously. The 
survey by Galtsoff 4 in 1925 showed that the coastal waters comprise large areas 
which appear to be suitable for oyster culture. 
SUMMARY 
(1) The spawning season of oysters in Galveston Bay in 1929 was observed to 
begin at the end of March. At the end of August larvse were still in the water and the 
oysters still milky, indicating a spawning season of at least six months. 
(2) Spawning started when the average daily water temperature in Offatts Bayou 
was about 25° C. When 20° C. was reached the oysters were just beginning to 
develop mature eggs and sperms, causing them to appear milky. 
t Unpublished manuscript in the files of the Bureau of Fisheries. 
