78 DEPARTMENT OF THE NAVAL SERVICE 
7 GEORGE V, A. 1917 
the assumption is that the spat grow equally and similarly and uniformly, certainly 
rather unlikely. We need to have some careful research made on this problem. 
Next let us consider the value of tar as a coating for oyster shells; does it improve 
shells to varnish them with coal tar? Striving to not crowd these pages with detailed 
tables, we shall give only the results of counting the spat. The figures show that 
per unit area, the tarred surface captured only two-fifths as many spat as did the 
unvarnished shell; that the smooth side and rough side of the plain right valve were 
equal; that tarring reduced the number of outside spat to half, and those setting inside 
to a quarter as many as would have otherwise set. For the left valve, there was no 
difference between the plain and tarred surfaces outside, but a reduction to a fifth 
for the inside. The left valves caught more than twice as many spat as did the right 
valves. This was true respectively both for the plain and the tarred surfaces. We 
had long ago established similar ratios for these valves; yet we showed above that in 
“eluckers ” lying in the normal position, it is the right valve that gathers most spat. 
The reason the left, free, valve and outside surface is superior to the right, is due 
to the fact that the silt fails to bury its edges as quickly as in the case of the flatter 
valve, when both are free. 
The outcome of these researches is to suggest further studies with cultch coated 
with the composition (equal parts of lime, sand, cement) used for tiles in Europe. 
This is useful in view of the scarcity of cultch in Prince Edward Island. 
October 4, Mr. McKenzie gathered samples from Ram island, placed there August 
21. These shells held only “deckers” (Crepidulas). October 5, Mr. McKenzie 
gathered samples of Curtain island shells left there August 21, and therefore exposed 
for forty-five days. Two of them were tarred shells, carrying Crepidulas both on the 
tarred and the plain areas. The plain shells have but one spat on one surface (rarely 
on both). They range from 4 to 10 millimeters in diameter. Fragments of a Mya 
shell carry four spat of 16 to 20 millimeters in diameter. On the supposition that 
the largest had “set” as early as mid-August, they would be not more than fifty days 
old, and in the ease of the largest spat, a growth of 400 mu per day must have been 
attained on an average. Of course the growth is absolutely more rapid the older 
the spat, though it may relatively be less so. It is desirable to have careful studies 
made on growth, and we await with interest the results of Professor Robertson’s 
researches on this subject. 
CONCLUSION. 
We have found that oyster propagation in Richmond bay shows the effects of the 
very considerable depletion indicated by statistics; but there are still areas, where 
careful planting of cultch will capture a fair set of spat. We wish to emphasize the 
necessity of pushing the practice of raising oysters from the seed, by artificial culture, 
insistently, persistently, consistently, and intelligently and scientifically, as the only 
way to restore the bay to its original productiveness, or even to keep its beds from 
ultimate destruction. But if the practice of scientific oyster culture be encouraged 
and developed, there is no reason for doubting that the maximum production formerly 
exhibited by this bay, under nature, and by fishing methods, can be increased very 
much. We do not think that every one of the 32,000 acres in this domain, can be made 
productive, but there is a good possibility that a quarter of this acreage may be made 
productive, and when that time arrives the annual product should be nearly a million 
bushels. It is worth while to strive for that figure, even if it may take a long while 
to reach it; by thus striving, it is certain that the present production will be increased 
many fold, to say nothing of conserving the very life of the oyster industry. If we 
go not forward we shall surely drift backward. 
