ECOLOGICAL LIFE HISTORY 

 Duration and Intensity of Oviposition 



Information on the duration of the spawning period of the oyster drill in 

 native waters in different latitudes is abstracted in Table 4 . The noticeable 

 variations in the onset of spawning in one region as well as along the entire east- 

 ern coast of North America and in England undoubtedly reflects not only annual 

 differences in water temperatures in the spring but incomplete information as well. 



For example, Gibb's date represents only a single observation, and Bumpus 

 and Fedenghi, the latter for Beaufort, give no termination dates for the spawning 

 period in these states. Engle's (1940) date for initiation of spawning in Long 

 Island Sound is almost a month later than Loosanoff s date for the same sound; it 

 is possible that Engle did not observe the earlier spawnings, or that, since spawn- 

 ing in warmer inshore waters occurs at an earlier date than in the offshore colder 

 waters, the two sets of observations were made in waters differing considerably 

 in their thermal characteristics. However, Loosanoff made his records over a 

 period of several years and thus probably more closely reflects the overall spawn- 

 ing picture in the area . The spawning date in the spring in Delaware Bay given by 

 Galtsoff et al. and by Stauber differ by almost a month; Stauber (pers. com.) notes 

 that the date of Galtsoff et al. is not representative for Delaware Bay. Again 

 because of Stauber 's long range studies in this bay it is probable that his observa- 

 tioi s more accurately reflect the conditions there . 



In Cape Cod waters Galtsoff et aL (1937) found that the bulk of the spawning 

 occurred in the early part of the summer, and that a second smaller spawning 

 occurred in late September. Cole (1942) made a similar observation in England 

 where he found that the bulk of spawning took place during May and June after which 

 it declined until late August and September when a second much smaller spawning 

 took place. The same phenomenon is reported by Stauber (1943) for Delaware Bay 

 where his rather complete information shows that over a period of years spawning 

 began in May, reached a peak in June, and ceased almost entirely in August; and a 

 second less intense wave appeared in September and this ceased in October or 

 November, depending on the temperature of the water . Stauber found that the 

 second wave of spawning was performed chiefly by young drills maturing in the 

 late summer. Galtsoff et al. (1937) observed a more or less continuous spawning 

 over a period of 7-1/2 months in Chincoteague Bay, Virginia, with a climax during 

 June and July; and Fedeiighi (1931c) noticed that spawning continued throughout the 

 summer in Hampton Roads, Virginia, and in Beaufort, North Carolina, and gradually 

 decreased in intensity in the fall . Neither mentioned a second peak of spawning in 

 the fall , The occurrence of late spawnings in at least three different regions 

 suggests that maturing young drills may oviposit in the late fall throughout much of 

 their northern range . 



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