The environmental factors controlling spawning of oysters in the Apalachicola area were investigated with particular regard to temperature. The principal literature is reviewed. Regular observations of temperature, salinity and spatfall intensity were made at nine stations covering
a distance of approximately 30 miles of Apalachicola Bay. Isolated spawning did not occur below temperatures of 22.5° C. Mass spawning took place only when the temperature rose to at least 26.0° C. On two occasions mass spawning occurred simultaneously at all stations in the eastern
part of the Bay but not in the western part. The average temperature is lower in the western part than elsewhere and also fluctuates more rapidly. Since the temperature necessary for mass spawning is higher than reported elsewhere in the United States, the possibility has been suggested that
there are physiological races of oysters. In the absence of observations on inheritance of this characteristic when oysters are transplanted it is considered that the interaction of a number of environmental factors upon the maturing gonad may modify the temperature reaction and that it is
not necessary to postulate racial differentiation.
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