26 DEPARTMENT OF THE NAVAL SERVICE 
7 GEORGE V, A. 1917 
may become such, even in the summer, that a fish cannot get a good food supply for 
some time, and the growth is checked. That there are not more of these checks goes 
to show what an abundant and well-distributed fauna there must be in the sea. Fish 
must be subject to periods of ill health, as all animals are, and during such times 
growth may be seriously retarded. This would account for the small amount of 
growth sometimes found between two successive winter checks. 
Regenerated scales show that fish are subject to injury. As on the regenerated 
seales, only those rings corresponding to those formed afterwards on the normal scales 
appear, leaving the central portion of the scale blank. The time of the injury is thus 
indicated. If the injury is a serious one the normal scales on the fish may show a 
check on account of the retardation of growth due to the drain on the system in 
recovering from the injury. These checks may or may not decrease the total amount 
of growth for the year. In some cases it does noticeably, but in others the later 
growth seems to have been accelerated so as to fully make up for the lost time. 
At first such extra checks may cause considerable confusion in scale reading, but 
after the normal scale becomes familiar, such checks, with rare exceptions, may 
readily be distinguished from the regular winter checks. 
RATE OF GROWTH. 
Since data as to length and weight of the fish from which the scales for this 
investigation had been recorded, these scales became available for a study of rate of — 
growth. Since that time other material has been added. Some of this additional 
material was obtained from the Departure Bay fishermen, and hence is comparable 
to the previous material; some was obtained from the cannery at Nanaimo, some 
from a cannery at New Westminster (these were caught in the Fraser river), some 
from the Vancouver fish companies (from the Skeena and Campbell rivers), some 
from the cannery at Uchucklesit, Barkley sound, and 2a small but interesting collec- 
tion from Mr. R. B. Heacock, Seabright, California. To those in charge in all these 
cases my thanks are due. 
The lot is rather a composite one and, for some purposes, a large number from 
one locality taken at nearly the same time would give better results, but for other 
purposes, as this material contains data from specimens of all ages taken at all times 
of the year, from widely different localities, it is especially suitable. 
In studying the rate of growth of the spring salmon it must be recognized, in 
the first place, that there are two types to be considered. Most observers have realized 
that some salmon migrate from the fresh water to the sea as fry, when they are four 
or five months hatched, while others remain in the fresh water throughout the first 
year and go down early in the second year as yearlings or fingerlings. The whole 
scale theory must fail if there are not two types of scales to corresvond, but if doe 
not. The most casual observer could not fail to notice that the central portion of 
the scale may differ materially from the corresponding portion of the scale of another 
individual. There is no doubt that Gilbert’s interpretation of this central portion 
of the scale in the two types of this species is correct. 
The individual that migrates as fry has no scales when it reaches the salt water, 
and consequently there can be no record on the scale of life in fresh water. The scale 
starts to develop soon after migration, the growth is rapid, and although the late 
start is a big handicap, the growth in the remainder of the year is slightly greater, 
on the average, than that of the whole second year. There is this difference, how- 
ever, the fish in its first year does not seem to be able to stand adverse conditions as 
well as the older fish. They may not be able to partake of as great variety of food. 
Tn consequence, the distance between the rings on the scale at times start to narrow 
earlier so that the summer growth gradually passes into the winter growth without 
giving the appearance of a distinct winter check. The change from the winter 
