GROWTH AND MATURITY OF SALMON IN THE OCEAN 
61 
Since the data on which this paper is based were taken entirely during the 
months from May to September, inclusive, the trends that have been calculated 
for the fish taken in the ocean represent the average slope of the growth curve 
during the period of most rapid growth. In order to show the general appearance 
of the total growth curve for chinook salmon, these trends have been used in pre- 
paring Figures 22 and 23, showing growth curves for fish with the ocean type of 
nucleus and with the stream type of nucleus, respectively. Such a use of these 
data is not strictly justified, as the data were all taken during a single year (1919), 
so that the individuals belonging to each separate age group came from different 
broods. The fish in their second year came from eggs deposited in 1917, those in 

7 
o 


o 
0 
0 
0 
0 
0 — 
t 
t- 
1 
SCCOHO YEAR 
THIRD YEAR 
FOURTH YEAR 
FirTH YEAR 
Fig. 22. — Growth curve of chinook salmon that migrated seaward as fry (scales with ocean type 
of nuclei). Data from fish taken in the ocean near the mouth of the Columbia River. Solid 
lines show the trends of growth during the fishing season; broken lines indicate roughly the 
probable course of growth during the remainder of the year; circles show the size of chinook 
salmon taken in the Straits of Georgia, as given by Fraser. Fraser's measurements did not 
include the caudal rays, while our's did 
their third year from the brood of 1916, and so on. The most logical method for 
preparing such a growth curve would be to have data over a series of years so that 
the growth of the fish derived from a single brood year could be obtained. Lacking 
this, it has seemed desirable to present in this form such data as are available. 
In the illustrations the calculated trends are shown by the solid lines, and the 
trends for successive years have been connected by dotted lines. No data are 
available upon which to base the form of these connecting lines. They have there- 
fore been drawn in "by eye." The resulting growth curve probably represents 
fairly well the average size of these fish at different ages and at different seasons. 
Some error is doubtless due to the use of a straight-line trend as showing the size 
during the period of rapid growth. The growth during the first and the last parts 
3210°— 25t 4 
