450 
BULLETIN OF THE BUREAU OF FISHERIES 
manner during the year and the two bays are similar in this respect. During late 
winter the pH rises rapidly from a low of about 7.8, reaching the maximum of about 
8.3 in April. It then drops rapidly until midsummer, after which it is relatively stable. 
This is discussed further below. 
The mode of sampling on the oyster grounds involves some lack of constancy 
throughout the year because all samples were taken during the day, so that for a large 
part of the year the tide was relatively high while in summer the dikes were exposed. 
A better picture of the high-tide salinity and pH was obtained by making studies in 
the deeper channels a short 
distance below the oyster 
grounds, off Corters Point 
in Oyster Bay and Maple 
Point in Mud Bay. That 
the results may be used to 
indicate conditions obtain- 
ing on the oyster grounds is 
shown in table 5, in which 
the surface temperature, 
salinity, and pH are com- 
pared for three places in 
Oyster Bay during summer. 
The salinity off Corters 
Point and Deepwater Point 
is almost identical with 
that in the exposed dikes, 
although in the last the 
temperature and pH are 
decidedly different because 
of exposure to sunshine and 
warm air and the respira- 
tory activity of oysters and 
other organisms. 
To show briefly the an- 
nual variation in the waters 
of the two bays the average 
monthly values of salinity 
and pH at surface and 
bottom for Corters Point 
(Oyster Bay) and Maple 
Point (Mud Bay) are given 
in table 6 for 2 consecutive j r ears. The surface salinity in Oyster Bay throughout 
the year is generally higher than in Mud Bay, though at the bottom the relationship 
is reversed and higher salinity prevails in Mud Bay. A similar difference was noted 
above with respect to the water over the oyster grounds of the two bays at low and 
high tide. The same average values are reproduced graphically in figures 10 and 11. 
The lowest salinity is to be found in late winter, near the end of the rainy season, 
and early in spring the gradual rise in bottom salinity begins. The bottom salinity 
in Oyster Bay varies during the year from about 26 to 29 parts per mille, in Mud 
Bay from about 27 to 29.5 parts per mille. The difference between bottom and surface 
Figure 9. — Average values of salinity and pH of water on oyster ground (dike B ) in 
Mud Bay during 2 years. Summer samples were taken at low tide while during 
the remainder of the yeat bottom samples were taken. Compare with Oyster 
Bay, figure 8. 
