SPAWNING AND SETTING OF OLYMPIA OYSTERS 
481 
of spawning oysters reduced to a low level. For this reason the catch of seeds could 
not be expected to be as great as in the upper end of Oyster Bay, which retained more 
spawners. 
The results obtained on two grounds in Oyster Bay (dikes 5 and S) and on one 
typical ground each in Oakland Bay and Little Skookum are presented graphically 
in figure 25. On all of the grounds there were three periods during which setting was 
especially profuse. The 
graphs show the three max- 
ima as occurring early in 
July, at the end of July, and 
at the middle of August. 
The last maximum was 
somewhat later in Oakland 
Bay than in the other areas, 
but the first two were in 
all cases at almost the same 
time. The total length of 
the setting season was only 
about months, from the 
beginning of July until the 
middle of September, a full 
month shorter than in 1932. 
The first spat were found in 
Oyster Bay on July 3, and 
in Little Skookum the next 
day. In Oakland Bay the 
exact date was not noted, 
but the first bag of shells to 
bear spat was in the water 
from June 30 until July 7, 
indicating that setting be- 
gan at almost the same 
time as in Oyster Bay. 
In the season of 1933 
setting started later and 
stopped earlier than during 
any of the other years. The 
reason for this short season 
may be seen in the records 
of water temperatures (see 
table 1, fig. 7). The water warmed to the spawning temperature much later in the 
spring, and did not reach as high a level by the end of the summer as during other 
years, thus reducing the length of the spawning season. Also, as was pointed out in 
the section on spawning, fewer adults bore broods of larvae. 
JULY AUGUST SEPT. 
Figure 25. — Average number of spat caught daily per bag of shells on two grounds in 
Oyster Bay and one each in Skookum Inlet and Oakland Bay, 1933. Range of tide 
is also indicated. 
SEASON OF 1934 
In the summer of 1934 setting started on June 4, a month earlier than in the pre- 
ceding year, and continued until the end of September (see table 25, fig. 26). In both 
dikes (5 and S) there were again two distinct periods of setting, during June and early 
August, respectively. However, each period was of considerable duration and con- 
