216 
BULLETIN OF THE BUREAU OF FISHERIES 
30 
£<J 
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28 
27 
26 
25 
water, the salinity rises gradually, reaching the highest figure at the time of high 
water. 
TIDES 
The mean range of tide in Wareham River is 4.1 feet; the spring range of tide 
.9 feet. 
The velocity of the current in the channel and on the bars was measured with the 
Price electric current meter. The results are shown in Tables 4, and 5, and Figure 10. 
The highest velocity, 62.7 centimeters per second, was observed at two-thirds ebb 
on September 22 (spring- 
tide). At flood tide 
on September 28, the 
changes in the current 
velocities were rather 
irregular (fig. 10). As 
can be noticed from an 
examination of Figure 
10, the maximum veloc- 
ity of the tide occurred 
between the times of 
high and low water, 
and the time of slack 
water nearly coincided 
with them. 
The strength of the 
current running over the 
bars and oyster beds is 
much less than in the 
channel, its maximum 
velocity not exceeding 1 2 
centimeters per second. 
24 
; HIGH 
V 
W. 
j LOW W. 
1 
Y 
/ 
t 
/ 
! 
4 
1 
j 
/ 
/ 
/ 
✓ 
/ 
1! 
V 
\ \ 
S 1 
1 
k i 
i S 
i | 
t 1 
s 1 
« 1 
/ \ 
/ '' 
j\ 
nrT’” 
V 
SALINITY OF WATE 
WAREHAM RIVER 
STAH, SURFACE. 
1 
R 
t HIGH 
w. 1 i 
J t 
LOW W. 
— Al 
G. 14, 1926 
28, •• 
^ 
— 'A/Vy 
1 
6 
9 10 II 12 I 2 3 4 
HOUR A.M. P.M. 
Figure 9.— Hourly fluctuations of surface salinity (per mille) during ebb tide, Station II, 
Wareham River, August 14 and 28, 1926 
SPAWNING AND SET- 
TING OF OYSTERS 
Beginning July 9, 
plankton collections 
were made every other 
day at different stations 
by towing a plankton 
net made of No. 20 silk 
for 5 minutes; samples 
were preserved in formalin for further examination. The first occurrence of straight hinge 
oyster larvae was recorded on July 21, and on the same day examination of oysters 
taken from the nearest bed showed that part of the oysters had spawned. Judging 
by the size, the larvie were not over 2 days old; it can be concluded therefrom that 
spawning occurred on July 19 or 20, when the temperature of the water was about 
23° C. The first spat (not over 1 day old) was noticed on the shells on August 
6 — 15 days after the first appearance of the oyster larvae in plankton. It is interest- 
ing to note that during July and August the oyster larvae were very scarce in the 
plankton samples, although later on the setting in the harbor was heavy. 
