600 
BULLETIN OF THE BUREAU OF FISHERIES 
These “size dates” were then plotted to represent the growth of the oldest scallops 
of the year’s (1926) spawning and were found to lie reasonably close to a straight 
line. (Fig. 19.) The junction of this line (growth curve) with the base line was 
taken to indicate a beginning of spawning by late July or early August. Although 
it was realized that linear growth would scarcely be truly uniform, with such notable 
change of size and season, it was thought that the “indication” might be sufficiently 
close to be helpful. 
Small scallops reappeared in the grass collections in June and continued through 
July, but without any evident increase and in such small numbers as to mean little. 
With the first August collection, however, a marked change occurred. Small scallops 
were present in numbers which indeed were small compared with those of the fall, 
JAN. FE3 HAR. APR. NAY JUNE JULY AUG. 5 EPT OCT NOV DEC 
Figure 20.— Spawning as indicated by the abundance, through 1927 collections, of scallops 2 milli- 
meters or less in length. (See Table 3) 
but large compared with those obtained since the disappearance months before. 
Increased numbers were obtained later in the month and impressive numbers early 
in September. The spawning period evidently began in July and became rather 
important in August and, therefore, is an affair of late summer, fall, and early winter, 
but chiefly of the fall. (See Table 3 and fig. 20.) Spawning has been obtained 
experimentally as early as August 26. 
This has affected the writer’s recommendations for conservation! regulation 
(Gutsell, 1928). Because various bivalves, and in the north the bay scallop, spawn 
during the period when water is warming, and indeed seem to depend upon a temper- 
ature rise for a spawning stimulus, the fact that scallop spawning here occurs princi- 
pally while temperatures are dropping is of considerable interest. 
The long-continued season explains the lack of a period of extreme abundance 
of very young scallops in highly productive areas. 
