4 



"^ 



474 BULLETIN OP THE BUREATT OF FISHERIES 



emptied into it. According to Collins (1925), the mean temperature of the river water 

 during these months is generally from 1° to 3° F. below the mean air temperature. 

 If we use this relationship as the basis for estimating the temperature of the river 

 water and also take into consideration the amount of river discharge, we find that in 

 1924 and 1926 the quantity of water emptied into Long Island Sound was much greater 

 than in 1925, and its temperature was decidedly below normal, while the smaller dis- 

 charge in 1925 had a temperature several degrees above normal. This applies espe- 

 cially to the months of April, May, and June, while during July and August, 1925, 

 the river discharge was greater and its temperatiu-e approximately 71° F., which is 

 virtually normal temperature for this period. During these summer months the river 

 water reaches its maximum temperature for the year, which generally is greater than 

 the mean monthly air temperature for each drainage basin. The river discharge in 

 July, 1925, served to reduce the salinity of the water in Long Island Sound and to 

 increase its temperature to a greater extent than did the smaller discharge in 1926. 

 The tables of salinity and water temperatures for these two months show clearly how 

 the amount and temperature of river discharge affected these conditions. 



The prime factors influencing the amount of river discharge are quantity, in- 

 tensity, and distribution of precipitation over each drainage basin. Records of pre- 

 cipitation along the coast must be taken into consideration, together with the dis- 

 charge of these two large rivers, in order to arrive at an approximation of the quantity 

 of fresh water that directly and indirectly, is emptied into Long Island Sound. Along 

 the coast of Connecticut is a belt of approximately 1,300 square miles that is drained 

 by a great many small rivers, and for this region precipitation records must be used 

 because figures of river discharge are not available. 



During the spring and summer months the drainage of fresh water from an area of 

 over 13,000 square miles to the north of Long Island Sound is important because (1) 

 it increases the temperature of the water over the oyster beds and (2) brings down 

 organic matter and mineral salts, both of which increase the production of plankton 



BIOLOGICAL OBSERVATIONS 

 CONDITION OF THE GONADS OF THE OYSTER 



Oysters in Milford Harbor were found to be ripe in the period from July 1 to 15, 

 the exact time varying in accordance with the previous water temperatures. In 1925 

 the gonads of the oysters were fully ripened by June 29, while in 1926 and 1927 this 

 condition was not found until nearly the middle of July. By stripping the oysters, a 

 small quantity of ripe eggs and sperms almost always can be found by July 1, but this 

 can not be taken to indicate that the reproductive products are fully developed. 

 The test employed for this purpose, which proved most reliable, was to place at least 

 a dozen oysters in water that was pumped at high tide and warmed to a temperature 

 of at least_25f_C. Under these conditions ripe oysters invariably spawned and dis- 

 charged the bulk of their products, while those that were not fully ripe generally did 

 not spawn or, at most, spawning consisted in a few contractions of the shell and the 

 release of but a small quantity of spawn. According to Galtsoff (unpublished report), 

 t he a ddition of jperm to the wat er will induc e spawning, and, in case the oysters failed 

 to spawn voluntarily, a small quantity of sperm from two to three oysters was added 

 in order to accelerate the process in case the temperature was not a sufficient in- 



