74 DEPARTMENT OF THE NAVAL SERVICE 
7 GEORGE V, A. 1917 
water, and 1016 in Indian river. The lowest, 1015, was recorded at the head of Trout 
river; the observation at the ‘head of Shipyard river, which was the only river that was . 
penetrated into the parts accessible only at high water, was exceptional. Here the 
salinometer read 1000 at 60° F. 
SPAWNING. 
It was easier to ascertain the progress of spawning from’ examination of the 
plankton, than by dredging for oysters and opening the same. Dredging on natural 
beds did not bring up many oysters, and we depended on oysters from planted beds 
secured under direction of those in charge. An oyster secured in March water on 
the 11th was filled with immature spawn, but next day samples at Ram island showed 
that their spawning was completed. On the 18th in Bentinck cove we found 
that spawning was hardly half through, as half of the oysters had not begun, 
and the others were only partly spawned out. Near the Barbara Weit, on McNeill’s 
beds, however, only a few oysters contained spawn. On the 14th, in Grand river, 
half-way between Southwest creek and Cross creek, we again noticed that half of the 
oysters were still in full spawn; but near Cross creek, all that we secured were empty. 
Dredging for oysters near the ferry failed to secure any samples. On the 24th, on 
MeNeill’s beds, there were still traces of spawn. On the 26th, oysters in March water 
were through spawning. Owing to the small number of samples opened, and few 
observations, only general conclusions can be drawn from these observations, viz., 
that before the 20th there was abundant spawn still present, and that after that date 
the oysters were nearly but not entirely through spawning. 
Turning to the plankton record, we find that fry which were probably ten days old 
were present August 5, but oyster plankton was not abundant until August 14; and 
these fry were also about ten days old. On the 17th they were advanced to 200 microns, 
indicating an age of about two weeks. On the 20th, and especially on the 21st, small, 
lately hatched fry were most abundant. Here was a climax in the spawning, which 
probably occurred on the 20th, a fine day following stormy weather. On the 25th, fry 
under 100 mu were scarce, but very abundant at that size, and not yet a week old. This 
day was a banner day for showing fry; they were abundant up to 320 mu. On the 26th 
and 27th there was an increase in the fry under 100 mu in size, but these had attained 
100 mu on the 28th. 
SPATTING. 
The study of spatting involves the determination of the date of “setting” (fixa- 
tion of the fry to cultch as spat). Also a study of the rate of growth and of survival; 
also the determination of the most suitable cultch and localities and other conditions 
favourable to this process. 
The date of spatting can be fixed by two independent sets of evidence: (1) obser- 
vations on the presence and abundance of the largest fry “ready to set”? in connection 
with the plankton data; (2) the “lifting” of the cultch, such as shells, from time to 
time, and giving them careful examination, after drying. Such shells should be spec- 
ially selected, the cleanest obtainable, and preferably have been experimentally placed 
at set dates. 
From the table given a few pages before, we learn that fry of spatting size (320 to 
400 mu) were present in relative abundance from August 14 to 17, and on the 24th 
and 27th. These fry were not nearly so abundant as the fry seen previously, of sizes 
260 to 8320 mu. There was a reduction of at least 60 per cent. Part of this reduction 
may be explained as due to the probable presence of a certain number on the bottom 
seeking suitable cultch, so that the net necessarily failed to catch them. Part of the 
reduction was probably due to destruction. 
When fry of 260 to 320 mu are compared with earlier stages, we find also a reduc- 
tion nearly as great, and while it is possible that the fry wiJl remain on the bottom 
