170 
BULLETIN OF THE BUREAU OF FISHERIES 
Table 9. — Average number of hours of activity of the oysters 
Temperature ranges, 0 
C. 
Item 
22-25 
23-26 
24-27 
25-28 
26-29 
27-30 
In running sea water, under oil - 
10.8 
8.9 
10.3 
12.2 
10.5 
10.2 
In running sea water 
8.8 
9.0 
11.0 
8.3 
9.2 
10.2 
In another set of experiments, simultaneous observations were taken on oysters 
kept under oil and in the control tanks. In these experiments water was supplied 
at the uniform rate of flow of 6 liters per hour to each of the oysters kept in glass 
aquaria tanks. Experimental tanks contained enough oil to make a layer 1 centimeter 
thick. The amount of oil varied from 300 to 350 cc. Water was not permitted to 
pass through the oil layer, both the intake and out-take tube of the siphon being kept 
under it. The results presented in table 10 are similar to other experiments. There 
was no significant difference between the behavior of the oysters under oil and in the 
controls, the average number of hours of activity being 11.2 and 11.8 respectively. 
Table 10. — Average number of hours of activity of oysters under oil and in controls 
Experiment number 
Date 
Number 
of days 
Temperature 
range (° C.) 
Average number hours per 
day open 
Kind of oil 
Experimental 
Control 
1 
Oct. 11-30 
20 
16-22 
5.75 
7. 25 
Pelto. 
2 
Oct. 19-24 
6 
18-22 
11.9 
9.5 
Do. 
3 
Oct. 26-31 
6 
16-20 
12.2 
16.0 
Do. 
4 
Nov. 1-7 
7 
18-21 
11.6 
12.8 
Do. 
5 
Nov. 11-16 
6 
11-18 
16.6 
10.6 
Do. 
6 
Nov. 19-25 
7 
11-17 
9.6 
10. 6 
Barre. 
7 __ 
Dec. 7-16 
10 
10-15. 5 
13.8 
17.2 
Do. 
8 
12 
10-17 
8.5 
10.5 
Barre sludge. 
i 74 
11.24 
11.83 
' Total days. 
The results of these observations show that presence of oil in the water failed to 
interfere with the muscular activity of the oyster and did not reduce the duration of 
their feeding. 
EFFECT OF OIL AND OIL WELL BLEED WATER ON THE RATE OF FEEDING OF OYSTERS 
The purpose of the experiments here described was to determine the effect of various 
concentrations of the water soluble fraction from crude oil and oil well bleed water 
on the rate of feeding of oysters. The importance of this matter from a practical 
standpoint can scarcely be overestimated. 
Growth and fattening of oysters depend on three major conditions: 1. Abundance 
of food organisms in the water; 2, percentage of time the shell of the oyster is open; 
and 3, rate of flow of food-bearing water through the gills. It is obvious that no 
matter how abundant food may be in the water, or how long the shell is open, very little 
food will be available to the oyster unless a current is maintained through the gills. 
Consequently, any substance which slows down the filtering activity of the gills acts 
to reduce the quantity of nourishment available to the oyster. In an extreme 
condition, a substance which reduces the rate of flow might eventually cause the 
death of oysters without ever being directly toxic. 
