1114 U. S. BUREAU OF FISHERIES 



summer, an extensive study of the influence of hydrogiapliic condi- 

 tions upon the oysters in the bay waters near Galveston. The in- 

 vestigations centered in a field laboratory on Offats Bayou, an arm 

 of the West Bay portion of Galveston Bay. Water temperatures and 

 salinity records were made daily near the laboratory and frequently 

 at other places throughout the bay. 



SpairniiK/. — The oysters started spawning at the end of March, at 

 a temperature of about 25° C. (77° F.), and larvte became extremely 

 abundant in the water especially during the following two months. 

 A fairly exact estimate of intensity of spawning was obtained by 

 townet collections of free-swimming larvae. The time and abundance 

 of setting was determined by planting wire bags filled with shells in 

 favorable locations. These were brought to the laboratory periodi- 

 cally for examination. The period of spawning near Galveston 

 lasted from the end of Marcli until at least September 1. and prob- 

 ably continuetl for another month, for the oysters still contained 

 spaVn. The bulk of the spawning, however, occurred in April, May, 

 and June. 



Setting. — Considerable evidence was obtained to show that the sa- 

 linity of the water is a controlling factor in the setting of oyster 

 larva? in this region. Although the water may be well populated 

 with oyster larvae, they will not attain the setting stage unless the 

 water contains 20 to 21 parts of salt per thousand. This is probably 

 why attempts to rehabilitate reefs and establish new ones by planting 

 oyster shells during spring and summer have failed. However, to 

 plant shells when the salinity is high enough should surely succeed, 

 for setting would then occur before the shells could become coated 

 with slime. 



Wire bags of shells were planted, and the set obtained proved 

 tne adequacy of this method in Gulf waters. As many as 40,000 

 spat per bushel of shells were ol)tained during two weeks at the 

 height of the setting period. Spat grew in the warm water at the 

 rate of about 0.3 millimeter a day in diameter, or 1 inch in two and 

 one-half months. 



Salt analyses, Galveston Bay. — With the cooperation of W. B. 

 Wardlow, of the Texas Department of Health, quantitative analyses 

 of the salts in various parts of Galveston Bay were made. The re- 

 sults show a remarkable variation in the proportion of the constitu- 

 ent salts present. Such fluctuations in the salts in solution in sea 

 water may probably be of great importance in the life of the oyster 

 and other organisms. The oyster is highly sensitive to such changes 

 in the water, and its feeding Jaehavior is readily influenced by sudden 

 changes. 



WASHINGTON 



Investigations in oyster culture in the State of Washington were 

 carried out bv H. C. McMillin. Headquarters were established on 

 Totten Inlet' (Oyster Bay) in April. Temperature and salinity 

 records were kei)t throughout the season. Spat collectors were put 

 out in all of the oyster-producing bays on the lower end of Puget 

 Sound and in AVillapa Harbor. Plankton samples were taken in the 

 open bay at high tides and in the dikes at low tide. 



A careful examination of all the beds of the State was made to 

 discover the presence of forms which had been brought in with the 



