FACTORS INFLUENCING THE SPAWNING AND SETTING OF 
OYSTERS IN GALVESTON BAY, TEX . 1 
J- 
By A. E. HOPKINS, Ph. D., Aquatic Biologist, United States Bureau of Fisheries 
CONTENTS 
Page 
Introduction 57 
Methods 58 
Description of Offatts Bayou 60 
The spawning season 60 
Sex of oysters 64 
Water temperature in relation to 
spawning 65 
Salinity and pH of water 67 
Observations on setting 70 
Growth of spat 71 
Determining dates of setting 72 
Page 
Observations on Setting — Continued. 
Setting periods during season 73 
Apparent influence of salinity on 
setting 74 
Abundance of diatoms 77 
Use of wire bags of shells as cultch 80 
Summary 81 
Literature cited 82 
INTRODUCTION 
The problems of oyster culture in the waters of the South Atlantic and Gulf 
coasts are decidedly different from those in the waters of the North Atlantic coast 
although the oysters are of the same species ( Ostrea virginica). On the Gulf coast 
the bays and estuaries are very shallow, and so the waters are readily affected by heavy 
rains and freshets as well as by differences in air temperature. The natural oyster 
beds, or reefs, are generally confined to a relatively narrow place between high and 
low tide levels and slightly deeper, and seldom occur more than 2 or 3 feet below low- 
water level. In more northern waters natural oyster grounds may be under 30 or 
more feet of water. 
Few actual oyster-cultural operations are carried on in Texas waters and the 
industry is limited chiefly to the removal and marketing of oysters from the public 
reefs. In the past this method has sufficed to supply the demand to a large extent, 
and the necessity for intensive oyster culture on private grounds has not been press- 
ing. In recent years, however, the oyster production of Texas, like that of many 
other States, has diminished, and increasing thought has been given to the possi- 
bilities of oyster culture by private individuals or companies. The Texas Game, 
Fish, and Oyster Commission is strongly in favor of production of oysters by private 
interests and has been attempting to pass legislation to permit the leasing of portions 
of productive public reefs as a stimulus to private enterprise. (Burr, 1928.) 
It was the purpose of this investigation to learn some of the more important 
facts concerning the reproduction of the oyster in Texas waters and on the basis of 
this information to make suggestions as to how best to develop ground for the pro- 
duction of oysters. Of greatest importance was the problem of finding means of 
obtaining seed oysters in abundance, and it was with this in view that these obser- 
vations and experiments were made. 
i Approved for publication Nov. 28, 1930. 
57 
