472 BULLETIN OF THE BUREAU OP FISHERIES 



No. 6 the range of salinity in 1925 was from 27.54 to 28.50 per mille and in 1926 from 

 27.36 to 28.74 per mille. These figures apply only to the summer months, July and 

 August, when conditions are comparatively stable. According to Galtsoff (un- 

 published report), there are seasonal variations in the salinity of the Sound waters, 

 the most noticeable of which is the freshening of the water at the time of spring 

 floods in April and May, when the salinity is lowest; while during the cold months 

 the salinity was found to increase gradually and reached the maximum for the year 

 in January. He foimd that in these waters the seasonal fluctuation in salinity was 

 a regular process, which repeated itself with certain constancy from year to year. 

 At his station at the entrance to Bridgeport Harbor the annual range in salinity in 

 1922-23 was from 24.7 to 27.8 per mille, an average of 26.2 for the year. 



HYDROGEN-ION CONCENTRATION 



The hydrogen-ion concentration of the water was determined for each station 

 by the colorimetric method and the values expressed in pH, in which no correction 

 has been made for salt error. In this locality the water is naturally alkaline and 

 during the summer ranges from a pH of 7.2 to 8.4. In plotting the average readings 

 for each station, we find that the pH increases from 7.6 at Station No. 1 to 8.2 at 

 Station No. 6 in the Sound. The lowest pH values were found in samples taken at 

 low tide following heavy rains, and the highest in afternoon samples taken in the 

 harbor near the time of high water. The pH was found to vary with the time of 

 day, depth, stage of tide, and amount of river discharge. An example of the surface 

 and bottom changes in pH during a complete tidal cycle is shown in Figure 6 for 

 a series of observations taken on August 24, 1925. In samples taken in the morning 

 the pH of the surface water generally was found to be a little lower than that of the 

 bottom water. In the afternoon the reverse was true and the pH of the surface 

 water was from 0.1 to 0.2 higher than it was on the bottom, probably as a result of 

 increased photosynthesis in the warmer surface layer. In considering the character- 

 istic changes in pH dming both summers, we find that during July the average pH 

 value was 7.8, while in August the readings became higher and ranged from 8 to 8.2. 



RIVER DISCHARGE 



The importance of river discharge in the ecology of the oyster is shown clearly 

 by the fact that oysters are found growing naturally only in those partially inclosed 

 bodies of water along the coast where the salinity is reduced considerably by the 

 drainage of fresh water from the land. On its northern shore Long Island Sound 

 receives the drainage from virtually the entire State of Connecticut and a large 

 portion of Massachusetts, Vermont, and New Hampshire, and it is here that we find 

 thousands of acres suitable for the growth of oysters, as shown in Figure 2. There 

 are over 30 coastal rivers that discharge into the Sound, of which the Connecticut 

 and Housatonic are the largest. 



The Connecticut River receives the drainage from an area of approximately 

 11,000 square miles and the Housatonic from 1,500 miles. The lowest point for which 

 records of river discharge are available is Sunderland, Mass., on the Connecticut 

 River, and Falls Village, Conn., on the Housatonic River. The mean monthly dis- 

 charge of the rivers at these points is shown in Figure 27 for the period from April 

 until August in the years 1924, 1925, and 1926. The quantity of water discharged 



