SPAWNING AND SETTING OF OLYMPIA OYSTERS 
483 
SEASON OF 1935 
Figure 26- 
Records for this year were analyzed completely only in dike 5, since it had already 
been well demonstrated that different portions of the bay differ only in the number of 
spat setting, while the time is the same. The results are given in table 26, and figure 
27, and they show a marked 
similarity to those of previ- 
ous years in that there are 
two major divisions of the 
setting season. After start- 
ing on June 17 setting in- 
creased in frequency, reach- 
ing the first maximum at 
the end of the month. A 
second, smaller maximum 
centered about July 20. 
From July 29 until August 
9 there was a time when 
almost no larvae attached, 
and then the second major 
setting period started, 
reaching a peak soon after 
the middle of August. Al- 
though the season was practically over early in September a few spat were caught up 
until mid-October, making a total setting season of nearly 4 months. 
Other bags of shells were planted in the same dikes at more frequent intervals, 
in order to give more exactly the times of the maxima. This series will be considered 
below with respect to the analysis 
of the significance of the results. 
SETTING SEASONS, MUD BAY 
Although parallel to Oyster 
Bay and separated from it by only 
a few miles, Mud Bay is somewhat 
different hydrograpliically, as was 
indicated above. Also, the spawn- 
ing and setting activities of the 
oysters are so different in the two 
bodies of water that they must be 
treated separately. It was shown 
in tables 14 to 17 that spawning 
does not begin until relatively late in Mud Bay, sometimes as much as 3 weeks 
later than in Oyster Bay. Setting is therefore similarly later. 
-Average number of spat caught daily per bag of shells on two grounds 
Oyster Bay, 1934. Range of tide is indicated also. 
Figure 27. — Average number of spat caught daily per bag of shells in dike 
5 (Oyster Bay) in 1935. See also figure 33 for results with more fre- 
quently planted cultch. 
Table 27. — Number of spat caught per bag of shells on two grounds in Mud Bay, 1931 
Date 
planted 
Date re- 
moved 
Num- 
ber of 
days 
Dike B 
Dike D 
Date 
planted 
Date re- 
moved 
Num- 
ber of 
days 
Dike B 
Dike D 
Total 
number 
of spat 
Num- 
ber of 
spat 
daily 
Total 
number 
of spat 
Num- 
ber of 
spat 
daily 
Total 
number 
of spat 
Num- 
ber of 
spat 
daily 
Total 
number 
of spat 
Num- 
ber of 
spat 
daily 
June 17 
June 
29 
12 
6,626 
552 
6, 240 
520 
June 29 
Aug. 7 
9 
0 
0 
0 
0 
June 25 
July 
1 
6 
7, 390 
1,231 
3, 120 
520 
Aug. 7 
Aug. 21 
14 
120 
8 
414 
30 
June 29 
July 
9 
10 
6, 949 
695 
10, 037 
1,003 
Aug. 21 
Aug. 26 
5 
60 
12 
323 
65 
July 9 
July 
17 
8 
3, 021 
377 
3,709 
463 
Aug. 26 
Sept. 10 
15 
331 
22 
628 
42 
July 13 
July 
25 
12 
331 
27 
228 
19 
Sept. 5 
Sept. 26 
21 
871 
41 
1,988 
95 
July 20 
Aug. 
7 
18 
0 
0 
0 
0 
Sept. 26 
Oct. 8 
12 
0 
0 
103 
8 
