78 COMMISSION OF CONSERVATION 



European oyster retains the eggs within the shell and between the gills for 

 some time after they are extruded from the ovary through the oviduct, 

 during which time they develop into straight-hinge shelled stages. The time 

 at which these pass out into the sea does not correspond with the time of 

 spawning of the common American or Canadian oyster. It is the time 

 when the eggs of the European oyster pass from the ovary into the mantle- 

 cavity that corresponds with spawning in the American oyster, and this 

 is even more difficult and less likely to have ever been directly observed. 



Sprat (1669) wrote, "In the month of May the oysters cast their spawn." 



Brack (1690) thought that oysters produce spawn towards the end of spring, dur- 

 ing the entire summer, and in the beginning of autumn. 



Davaine (1852) specifies from the beginning of June to the end of September. 



Huxley (1883) : " During the summer and autumn months, from as early as May 

 to as late as, or even later than, September." 



Except for local differences of temperature, food, enemies, and the 

 like, the accrued knowledge in the United States on this and other ques- 

 tions relating to the oyster, is of great value to Canada. 



Window (1878), writing of Tangier and Pocomoke sounds and Chesapeake bay, 

 remarked, "The spawning season was said to be from May until August inclusive, 

 though most of the spawning was done in June and July." 



Brooks (1880) : " Oysters in from one to six feet of water in the vicinity of Crisfield, 

 probably spawn between the middle and end of May, but oysters with ripe eggs were 

 found in water from five to six fathoms deep from the first to the thirtieth of July, 

 although most of them spawn late in June." 



Ryder (1882-3) : " In the region of the Chesapeake the most important spawning 

 period seems to extend over the months of June and July, but considerable ripe spawn 

 may be found even much earlier and later than this." 



Nelson (1900): "Late in June and early in July this spawn is 'ripe' and is thrown 

 out of the oysters, sometimes so abundantly as to make the water look as if milk had 

 been poured into it." Also (1906): "It is true that eggs of some sort were present 

 in oysters from May to September, but we have good reason to believe that the present 

 season's supply of natural oyster seed was all produced during the last two weeks of 



June, if, indeed it was not still shorter By the end of June the large 



naturals at Barnegat had completed their spawning. The young oysters were on the 

 point of beginning to fill up with spawn a second time. This spawn, which was thrown 

 out during July, does not seem to have played any appreciable role in producing spat." 

 Again (1909): "Hence it is that oysters taken from the warmer southern waters and 

 planted in the colder northern waters will fail to propagate, although well filled with 

 spawn, and that northern oysters taken into more southern regions will spawn earlier 

 than the natives." 



In Canada, during the long winter and cold spring, the reproductive 

 cells in the ovaries of oysters make slow progress. But with the arrival 

 of the warm weather of May and June, and the abundance of microscopic 

 food organisms that accompany it, the genital elements rapidly come to 

 maturity. Late season, shaded localities, deep water, cold currents, in- 

 dividuality of the oyster, etc., may cause delay here and there, but the 

 long period of cold, followed by the relatively short spell of very warm 

 weather, tends to restrict spawning to a briefer term and to bring about 

 a degree of regularity or periodicity. 



It would require several years of observation and a careful systematic 

 examination of a very great number of specimens from different localities 



