INVESTIGATION OF OYSTER SPAWNING, ETC., MILFORD, CONN. 



479 



in 1925 and 1926 and its relation to tide and temperature arc shown in Figure 30. 

 Heavy and complete spawning of the harbor oyster s occurred on July 13 in 1925, 

 but not until August 1 in 1926. Similarly, spawning in Long Island Sound at Station 

 No, 6 was 17 days earlier in 1925 than in 1926. IjiJ^92^^pawningj)ccurred more than 



9g 





■< 





9g 

 8o 



/ J i 7 9 W \Z \5 \7 \% 21 23 25 27 29 31 

 JULY 



FiGUHE 30.— Correlation between range of tide, temperature, and the spawning of the oysters 

 during the summers of 1925 and 1926 



tw o we e^jeailierJJi HTi h»s hppn ^bseryed^ duri ng the £ast^eyen^yearsjjtid_wasjlue to 

 the higher water temperAtureu.and^arly_rix)enirtg_o f th e oysters during July, of that 

 j^r. Though in 1926 the water in the harbor reached a temperature of 22.4° C. 

 on July 10, spawning did not occur, as the oysters were unripe at this time. During 

 both years the heaviest spawning of the oysters in the harbor was found to occur 

 after the water had reached and maintained for a few days a temperature of from 

 20° to 21° C. 



The part played by the tide in increasing water temperatures during July and 

 August has been discussed previously, and its relation to the time of spawning in 

 1925 and 1926 is shown clearly in Figure 30. Inboth years, the majority of the 

 oysters sp awned at the end of the July, " full-moon tid al period," when the water 

 was brought to a favorable spawning temperature. In 1927, spawning of the oysters 



