464 
BULLETIN OF THE BUREAU OF FISHERIES 
SPAWNING SEASON 
The spawning period of the Olympia oyster appears to be quite different from 
that of 0. mrginica in Long Island Sound, as described by Prytherch (1929). In that 
place the oysters spawned prolifically on a particular day, when water conditions 
were favorable, so that the time of setting of the larvae could be exactly determined 
with reference to the time of discharge of the eggs. During several years, according 
to Prytherch, the first spawning was relatively light, and was followed about 2 weeks 
later, during the next period of spring tides when the water was warmer, by more 
general spawning. 
The native oyster, as described by Stafford (1914), spawns during a period of 
about 2 y 2 months. According to this author, in 1913, in British Columbia waters, 
spawning occurred from about May 20 until the end of July, with the maximum 
spawning activity at the middle of June. On the coast of southern California Coe 
(1931a-1932b) found that spawning in this species continues for a period of about 
7 months of the year. In the same manner, 0. virgivica on the Gulf coast spawns 
during many months (Hopkins, 1931b). 
Table 13.- — Percentage of oysters bearing larvae in Oyster Bay 
Date 
Number 
opened 
Number 
gravid 
Number 
not 
gravid 
Percent 
gravid 
Date 
Number 
opened 
Number 
gravid 
Number 
not 
gravid 
Percent 
gravid 
11)31 
' 1931 
May 25 _ 
15 
7 
8 
47 
July 2 
30 
4 
26 
13 
May 27 
15 
6 
9 
40 
July 8 — 
37 
3 
34 
8 
May 29__ 
10 
2 
8 
20 
July 9 - 
64 
3 
61 
5 
27 
4 
23 
15 
July 10. . . . 
28 
3 
25 
11 
June 19 
34 
8 
26 
24 
July 15. 
53 
0 
53 
0 
June 21 
20 
3 
17 
15 
July 24 
30 
0 
30 
0 
11 
1 
10 
9 
July 27 
21 
3 
18 
14 
June 27. . 
29 
2 
27 
7 
Aug. 8 
20 
0 
20 
0 
Table 14. — Percentage of adult oysters bearing embryos ( E ) and conchiferous larvae ( C ) in dikes 5 
and S ( Oyster Bay) and dike B ( Mud Bay) during 1982 
Date 
Dike 5 
Dike S 
Dike B 
Date 
Dike 5 
Dike S 
Dike B 
E 
c 
E 
c 
E 
c 
E 
c 
E 
c 
E 
C 
12 
July 1 
13 
1 
4 
6 
19 
12 
2 
5 
1 
21 
20 
3 
4 
13 
4 
8 
4 
24 
32 
3 
5 
5 
27 
25 
11 
6 
6 
10 
30 
26 
13 
8 
3 
6 
12 
31 
15 
25 
9 
9 
2 
15 
40 
11 
10 
8 
3 
14 
3 13 
12 
6 
1 
4 
15 
28 
13 
11 
8 
6 
12 
16 
14 
10 
8 
1 
25 
15 
16 
6 
10 
7 
30 
16 
5 
11 
5 
15 
18 
17 
4 
8 
13 
11 
12 
4 
1 12 
19 
7 
14 
7 
19 
20 
18 
4 
15 
3 
5 
2 
8 
21 
5 
2 
16 
2 
11 
22 
2 
11 
4 
17 
5 
4 
4 
25 
3 
8 
4 
6 
18 
4 
10 
26 
6 
20 
5 
12 
4 
27 
4 
6 
21 
5 
28 
8 
22 
5 
30 
6 
23 
5 
4 
2 
24 
4 
2 
4 
2 
2 
10 
27 
5 
12 
4 
1 
28 
5 
5 
1 
4 
29 
2 
5 
8 
2 
31 
i 
1 No oysters opened before June 13. 
1 No oysters opened before June 3. 
