SCALES OF THE SPRING SALMON 25 
SESSIONAL PAPER No. 38a 
With temperature and salinity eliminated as primary factors, the main emphasis 
must fal] on the only other known variable that could have direct bearing on the 
growth of fish, viz., the food supply. That fish do not differ from other animals in 
which growth is accelerated by regular, suitable feeding, is shown by the success that 
attends the feeding of fresh-water fish in ponds, lakes, and streams. On the other hand 
fish, like other animals, cannot maintain normal growth if food is lacking or is insuffi- 
cient in quantity to keep the various processes active. Existence may be continued 
for some time under such conditions, but it must be at the expense of the nourishment 
and energy stored up in the body. While that is being drawn upon, growth must be 
retarded or stopped altogether, and the weight may be considerably reduced. 
The scale, like any other organ of the body, must be affected as the body as a who'e 
is affected, hence the variation in the food supply, even without any other important 
factors, could account for the difference in the rate of growth. 
In fishes like the salmon, where a portion of the life is spent in the fresh water 
and the remainder in salt water, there is a great disparity of growth during the two 
periods. The richness of the marine fauna as food supply, as compared with the 
fresh-water fauna, makes a decided difference in favour of the former. A difference 
in salinity, however, complicates matters,as far as evidence goes in this case. A better 
illustration is afforded by the difference in the rate of growth of a trout, eg., the 
cut-throat, in a small pond where food is scarce and in a lake where food is abundant 
or where there is a wider area over which to search for it. 
The variation in the food supply would seem to: account appropriately for the 
variation in rate of growth but, unfortunately, in the case of the spring salmon, the 
application is not self-evident. In the spring and summer, minute crustacea and a 
great variety of larve are abundant, hence such fish as the herring that feed on this 
should thrive better at that time of the year. The spring salmon takes this food also, 
but evidently eats many fish as well. Here comes the difficulty. To judge from the 
stomach contents, one might say that the salmon, by preference, feeds on the herring 
and the herring is abundant in the strait throughout the year. They are much more 
in evidence during the winter months, as the schools can readily be located near 
shore. During February and March they remain for long periods in the same locality, 
in the spawning season. Some of the salmon follow the herring into shallow water 
since a few individuals are caught in the herring nets, and I have seen them swim- 
ming around in a school of herring not far from shore. It may be that these are 
stragglers while the larger numbers remain in the deeper water where the herring 
congregate in the summer time. 
An entirely different explanation is possible. The spring salmon may prefer 
crustaceans, as the sockeye and the coho seem to do, taking fish only when the crus- 
tacean supply runs short. Their presence with the herring schools may be due to the 
fact that they, like the herring, are feeding on copepods. There is some basis for 
such conclusion, for spring salmon caught in the neighbourhood of herring schools 
-have been found to contain decapods, schizopods, amphipods, and copepods. At such 
time I have even found annelids of the Nereis type in their stomachs, the only evi- 
dence that I have seen that they are ever bottom-feeders after they leave the fresh 
water. Fishermen with spoon bait often catch many salmon right in the herring 
schools, while herring bait at such a time is useless. Jf crustaceans make up the 
main part of the food supply, then they would fare better in spring and early summer 
when the pelagic crustacea are so numerous. In the winter time they take to the 
herring in the extremity of hunger, as being the chief food available, enough to keep 
them alive but not enough for ample nourishment for growth equivalent to the 
summer growth. 
If retardation of growth in the scale is due to the lack of suitable food, an 
explanation is readily available for the extra checks that appear between the regular 
winter checks, or at the margin in fish caught during the summer. Local conditions 
