SPAWNING AND SETTING OF OLYMPIA OYSTERS 
455 
temperature; °c. 
Some of these data are given as averages for winter (December, January, and 
February) and summer (June, July, and August) in table 9 to indicate stratification 
of the water, for it has been shown by Nelson and Perkins (1931) that the behavior of 
oyster larvae may be determined 
by the salinity at different depths. 
The values for Maple Point (Mud 
Bay) are plotted graphically in fig- 
ure 13. In winter the salinity at 
surface and 3 feet is much lower than 
at greater depths but in summer the 
difference between surface and bot- 
tom is not so great. However, the 
pH in summer becomes lower toward 
the surface, probably because of 
planktonic animals, while in winter 
it is uniform from surface to bottom. 
In Oyster Bay (fig. 14) the salinity, 
temperature, and pH are almost 
identical from surface to bottom 
though during the winter the surface 
water is less saline and of slightly 
lower pH. The presence of the deep waters adjacent to the oyster grounds accounts 
for the high degree of stability indicated by these figures. 
Figure 13. — Vertical distribution of salinity, temperature, and pH off 
Maple Point (Mud Bay) summer (S) and winter (W) . Compare Oyster 
Bay, figure 14. 
Table 10. — Comparison of water near mouths of Mud Bay and Oyster Bay at ebb ( E ) and flood ( F ) 
tides during summer 
Mouth of Oyster Bay 
Mouth of Mud Bay 
Date 
Tide 
6 feet 
30 feet 
6 feet 
30 feet 
Tem- 
pera- 
ture 
Salin- 
ity 
pH 
Tem- 
pera- 
ture 
Salin- 
ity 
pH 
Tem- 
pera- 
ture 
Salin- 
ity 
pH 
Tem- 
pera- 
ture 
Salin- 
ity 
pH 
May 24 
E 
° C 
11.1 
28. 39 
8.2 
° C 
11.2 
28. 53 
8.2 
° C 
10. 1 
28.69 
8.3 
° C 
10.2 
28. 39 
8.3 
F 
12.0 
27. 86 
8.0 
12.2 
27.98 
8.2 
11.4 
28. 30 
8.2 
12.0 
28. 44 
8.2 
May 26 
E 
11. 1 
28. 39 
8.2 
11.2 
28.53 
8.2 
10.4 
28. 13 
8.4 
11. 1 
28. 27 
8.4 
F 
11.3 
27. 79 
8.3 
11.4 
28. 06 
8.2 
11. 1 
27. 85 
8.4 
11. 1 
28. 37 
8.4 
May 29 
E 
12. 1 
27. 98 
8.2 
12.2 
27. 85 
8.2 
11.2 
28.41 
8.2 
11.4 
28. 35 
8.2 
F 
12.4 
27. 65 
8.2 
12.4 
27. 66 
8.2 
12.4 
27. 85 
8.2 
12.2 
27. 75 
8.2 
May 31 
E 
12.1 
28.08 
8.2 
12.1 
28.08 
8.2 
11.0 
28. 16 
8.2 
10.3 
28. 56 
8.2 
F 
12. 2 
27. 83 
8.4 
12.2 
27.79 
8.3 
12.0 
28. 04 
8.2 
12.0 
28.69 
8.2 
June 2 __ 
E 
13.0 
28. 24 
8.2 
12.3 
28. 06 
8.2 
11.3 
28. 60 
8.2 
11.3 
28. 66 
8.2 
F 
13.2 
27. 90 
8.2 
12.3 
28.00 
8.2 
11. 1 
28. 40 
8.2 
11.0 
28.71 
8.2 
June 9 
E 
11.4 
27. 66 
8.2 
11.3 
27. 77 
8.2 
10.4 
28. 12 
8.2 
10.2 
28. 50 
8.2 
F 
12.4 
27. 77 
8.2 
12.4 
27. 95 
8.2 
12.4 
28. 16 
8.2 
12.3 
28. 37 
8.2 
June 14 
E 
14.0 
27. 99 
8.4 
13.4 
28. 30 
8.4 
12.3 
28.31 
8.4 
12.2 
28.64 
8.4 
F 
14.0 
27. 64 
8.4 
13.3 
27. 88 
8.4 
12.2 
28. 35 
8.4 
11.4 
28. 68 
8.4 
June 28 
E 
15.0 
28. 21 
8.2 
14.3 
27. 88 
8.2 
13. 2 
28. 51 
8.2 
12.4 
28.60 
8.2 
F 
15. 1 
28. 04 
8.0 
15.1 
28. 04 
8.0 
15.1 
28. 45 
8.4 
14.0 
28. 04 
8.4 
July 5 
E 
15. 1 
28. 48 
8.2 
15.0 
28. 40 
8.2 
13.3 
28. 85 
8.2 
13. 2 
28. 59 
8. 2 
F 
14.4 
28. 48 
8.2 
14.3 
28. 74 
8.2 
13.2 
28.74 
8.2 
13.0 
28.69 
8.2 
Average.. 
E 
12.8 
28. 10 
8. 22 
12.7 
28. 17 
8.23 
11.5 
28. 42 
8.24 
11.4 
28. 50 
8.25 
Average. 
F 
13.0 
27.87 
8.20 
12.8 
28. 02 
8. 21 
12.3 
28.24 
8. 26 
12.1 
28. 41 
8. 26 
Note.— E= ebb; F=flood. 
Further comparison of the two bays is shown by samples taken during summer at 
points near their mouths at depths of 6 and 30 feet at ebb and flood tides. (See table 10.) 
The water entering Oyster Bay is of a lower salinity than that going into Mud Bay, 
