EFFECTS OF PULP MILL POLLUTION ON OYSTERS 
169 
by retaking, and no significant variation was found. A series of samples was taken 
at one time, depending upon the location and upon the height of the tide. The height 
of the surface of the bed above the lowest oyster-bearing level was measured and 
three figures were obtained from each sample: The volume of shells, the number of 
live oysters, and the number of dead oysters. 
The first two determintions were easily made, but the number of dead oysters 
was more difficult to ascertain. There is no way of knowing how long any one oyster 
has been on the bed, but within a short time after death, the two valves, or halves, 
of an oyster shell break apart. We therefore, counted the number of specimens of 
Figure 43. — General map of Oakland Bay, Hammersley Inlet, and Pickering Passage 
which the two valves remained attached, and considered them as respresentative of 
the recently dead oysters. Doubtless, a number of valves were separated in handling, 
but this method appeared to be the only one available and by exercising due care a 
fair idea of the condition of the beds was obtained. The ratio between the number 
of dead and' live oysters does not give as complete a picture of the loss that has 
occurred over the oyster beds as one would desire, nor is it equally reliable for all 
areas from which samples were taken. Where the current is swift, empty shells are 
carried away quite rapidly, making the apparent percentage of dead oysters very 
much lower than actually is the case. However, the results show to a satisfactory 
degree the general conditions as they existed at the time of the survey. (Fig. 46.) 
