PEOGBESS IlSr BIOLOGICAL INQUIRIES, 1927 225 



numerous bays, harbors, and river mouths thousands of acres of 

 "bottom were found that could easily and profitably be developed 

 for producing seed oysters. In former times most of these areas 

 were prolific natural oyster beds. For example, in 1887 they pro- 

 duced over 240,000 bushels of oysters, most of which were seed, 

 but at present they are depleted to such an extent that it is difficult 

 to find a few oysters on them. It was found that modern cultural 

 methods could be applied to about 6,000 acres in the harbors. Just 

 outside of these harbors are thousands of acres of natural beds that 

 have been neglected sadly and are practically unproductive. The 

 most important of these is the Bridgeport and Stratford natural bed, 

 comprising 3.391 acres, which should be leased to the oyster growers, 

 who are capable of producing, by cultural methods, 10 times as many 

 oysters here as nature ever jDroduced at the best. A chart of the 

 Connecticut coast is being prepared, showing the areas suitable for 

 seed-oyster production and the distribution of salinity in these inshore 

 waters. 



STUDY OF THE FACTORS THAT CONTROL OYSTER SPAWNING AND SETTING 



H. F. Prytherch continued this study in Long Island Sound in 

 1927. The production of seed oysters on both natural and cultivated 

 beds has fluctuated tremendously from year to 3^ear; for example, 

 from more than 1,000,000 bushels in 1925 to virtually none in 1926 

 and 1927. In analyzing the various factors that may be responsible 

 for this, water temperature has been found to have the most important 

 effect in the control not only of the development and ripening of the 

 spawn but also of the time when sj^awning takes place. A striking 

 correlation between the success or failure of setting and changes in 

 temi^erature has been found. During the last six years setting has 

 been good when the temperature has been above normal and has 

 failed when it was below normal. The intensity of the set produced 

 €ach year depends largely upon the number and age of the oysters 

 on the beds, the temperature of the water just prior to spawning, 

 and an increase in water temperature to a degree that will produce 

 copious spawning. Recent studies indicate that daily and weekly 

 fluctuations in water temperature are controlled chiefly by the tide, 

 and that the maximum temperature necessary for spawning occurs 

 when the moon is full and 'the range of the tide greatest. 



A comparison of conditions in Long Island Sound each year with 

 those of preceding years has made it possible to determine, at least 

 one month in advance, when spawning will take place, when the 

 greatest number of oyster larvae will attach or set, and the intensity 

 of the set that will occur. LikcAvise, it can be determined in advance 

 how many shells should be planted in order to take advantage of 

 good sets, how rapidly the shells should be planted in order that the 

 work may be completed before setting occurs, and what beds Avill be 

 most favorable to obtaining a set under existing natural conditions. 

 This method has been tested during the past three years and has 

 proved to be reliable and of considerable help to the industry. 



The investigations at Milford have disclosed the chief factors that 

 control oyster propagation; and by systematically collecting repre- 



