430 BULLETIN OF THE BUREAU OF FISHERIES 



were seed oysters. On the cultivated beds of Connecticut similar fluctuations in 

 seed production during the last three years are representative of the experiences of the 

 industry since the initiation of oyster culture. For instance, the production of 

 seed oysters here ranged from over 1,000,000 bushels in 1925 to virtually none in 

 1926 and 1927. Through a detailed study of the conditions in Milford Harbor, it 

 was hoped that an understanding of this phenomenon might be obtained. The 

 objects of this investigation were to determine — 



1. The principal factors that influence and control the spawning of oysters. 



2. The occurrence and distribution of the oyster larvae. 



3. The zones in which setting or attachment of the larvse takes place. 



4. The conditions responsible for the occurrence of great annual fluctuations 

 in the intensity of setting or production of seed oysters. 



These studies were conducted imder the direction of Dr. Paul S. GaltsofF, in 

 charge of oyster investigations, to whom the author is deeply indebted for advice 

 in the course of the work and for criticism of the manuscript. 



The author wishes to acknowledge his appreciation of the valuable and cordial 

 cooperation rendered by the North Atlantic Oyster Farms (Inc.) in carrying on 

 these investigations, and especially the help, suggestions, and information given by 

 W. H. Raye, Capt. Charles E. Wheeler, and A. E. Loring, of that company, relative 

 to various studies of the oyster situation and for generously supplying oysters, 

 laboratory facilities, men, and boats for this work. Valuable assistance was received 

 from H. A. Marnier, of the United States Coast and Geodetic Survey, in the studies 

 of the tides and currents, and from the United States Weather Bureau and Geological 

 Survey in supplying climatological and river-discharge data. 



METHODS AND EQUIPMENT 



A small laboratory was established at the plant of the Connecticut Oyster Farms 

 Co., at Milford, Conn., where suitable arrangements could be made for setting 

 up tide and temperature recording apparatus and for boating operations. In Milford 

 Harbor and the adjacent inshore waters of Long Island Sound six stations were 

 established, as shown in Figure 1. These were visited regularly with a small cruiser 

 equipped for the collection of water and plankton samples and for making observa- 

 tions of general physical conditions. 



Water temperatures at the surface and bottom were taken at each cruising 

 station by means of a Negretti and Zambra deep-sea reversing thermometer, and, 

 in addition, a long-distance thermograph was set up at Station 2, which recorded 

 continuously the water temperatures on the bottom in the harbor. 



In collecting water samples for the determination of salinity and pH, a Greene- 

 Bigelow water bottle was lowered over the side by means of a meter wheel and 

 Lucas sounding machine. The samples were titrated in the usual way, using silver 

 nitrate against the international standard sea water and calculating the salinities by 

 means of Knudson's (1901) hydrographical tables. For the determination of the 

 hydrogen-ion concentration of the water, the colorimetric method was employed, 

 using cresol red and brom-thymol blue as indicators. No correction for salt error 

 has been made for the figures that are given. All the observations fall within the 

 range of the indicator cresol red. 



