60 
BULLETIN OF THE BUREAU OF FISHERIES 
DESCRIPTION OF OFFATTS BAYOU 
Since many of the observations reported in the following pages were made in the 
bayou some description of this small body of water is essential. (Fig. 5.) It is about 
2 miles long and varies from less than a quarter mile to about a half mile in width, 
and extends from West Bay into Galveston Island toward the Gulf. It is said that 
it is what remains of an old inlet connecting the bay and the Gulf. Though formerly 
shallow like most other such bayous along this coast, a few years ago extensive 
dredging was done for the purpose of filling in low land on the island. An irregular 
channel (fig. 5) now extends throughout most of the length of the bayou and is 30 
feet or more deep. Portions of the bayou, however, still remain shallow and on these 
are excellent private oyster grounds which produce well-shaped, fat oysters. The 
deep channel insures a fairly rapid exchange of water with West Bay and would not 
be expected to suffer great changes in salinity due to local rainfall. Three regular 
Figure 5.— Chart of Offatts Bayou showing oyster reefs, channels, and stations where shells were planted and plankton 
samples collected. See description in text. The laboratory was on the bank opposite the point marked A. Chart is 
based on preliminary survey by United States Engineers. Locations of oyster reefs indicated by Dolph Rogers, Galveston 
stations for plankton collections and two for the planting of bags of shells are indi- 
cated on the chart. 
THE SPAWNING SEASON 
It has long been known that the spawning season of oysters in southern waters 
is very long, as compared to the short season in Long Island Sound, for example. 
(Prytherch, 1929.) Moore (1907) concluded from a study of Matagorda Bay that 
the major spawning in Texas waters takes place between May and early August. Later 
Moore and Danglade (1915) said that most of the spawning season was limited 
between May 1 and October 1. These conclusions were drawn largely from obser- 
vations on the setting season, which, as will be shown, need not be closely similar to 
the spawning period. 
It has been established that oysters do not spawn until after the water temperature 
reaches 20° C. (Churchill, 1920; Nelson, 1928; Prytherch, 1929; Galtsoff, 1930), 
and that the length of the spawning season is limited, therefore, by temperature. 
Oysters from Galveston Bay were examined frequently during February and March 
(1929) in an attempt to locate as nearly as possible the exact time of appearance of 
well-formed eggs and active sperms in the gonads. 
