42 DEPARTMENT OF THE NAVAL SERVICE 
7 GEORGE V, A. 1917 
used is the same as that used in a prior paper on the life history of the spring salmon. 
In general, the winter checks show up more plainly in this species than in the spring 
salmon, so that there is seldom any difficulty in making out their delimitation. 
The scale appears first as a small, flat, almost circular body, which becomes the 
nucleus of the growing scale. At that stage of the appearance of this nucleus 
the fry is from 31 to 34 mm. long (in all measurements in this paper the length 
does not include the caudal fin rays), with an average of 32-5 mm. It is this size 
about the end of May or early in June. The rings then begin to form. From 
ten to fourteen appear in the first set; these gradually get closer together, although 
they are not very far apart at first. The last two or three may be dim, broken, and 
generally indistinct. They indicate the first winter check. At the time these are 
formed the food supply is at its lowest ebb, so that very little growth is taking place. 
In March or early in April the food supply becomes more abundant and the distance 
between the rings increases, showing more rapid growth, somewhat similar to that near 
the nucleus. At migration a decided increase takes place abruptly, due to the better 
supply of food in the salt water. It may be that the fresh water band for the beginning 
of the second year is entirely absent as some of the yearlings pass down to the sea too 
early to show spring growth in fresh water. More commonly the band is present, vary- 
ing in width with the length of time before migration takes place. 
Chamberlain! has reported that, in Alaska, a greater number of coho pass to the 
sea as fry than as yearlings. The evidence available for this region indicates a con- 
dition far otherwise. Out of nearly 400 examined for the purpose.of this research, 
only three showed indication of going to the sea as fry. These three were among those 
obtained at Neah bay on October 26. During the remainder of the summer the rings 
are formed as usual for salmon growth in the sea. The winter check follows and then 
the growth during the third summer, with the rings getting somewhat closer late in 
the fall when the fish goes up the stream to spawn. 
The scales of the three that went to the salt water as fry have the first-year growth 
in the nature of a broad band of distant rings next to the nucleus, followed by a 
winter check, the whole width of the band being similar to that of the second year, 
Since the first year shows no fresh-water growth, the second does not either, and the 
third year is similar to that in other scales. 
Even in the largest fish obtained there was no indication that the third year had 
been completed. As no one has recorded a fourth year specimen, if there are any 
such, they must be rare. 
The analysis of the results of examining the scales of nearly 400 fish, of which 
301 were in the third year, gives an admirable basis for comparing the rate of growth 
in the different years and in the different fish. As the fry is, on the average, 1-3 
inch long when the nucleus is developed, that amount has been taken from the total 
length in inches in each case and the remainder divided as the scale is divided by the 
winter checks. Then 1-3 inch is added to the first year value to obtain the length at 
the end of the first year. In these scales, the growth of the fresh-water portion of the 
second year was calculated also. 
In the whole number of fish in the third year, the least growth at the end of the 
first year was 2-4 inches and the greatest 4-1, with an average of 3)3. (AIl of the 
yearlings caught in the stream in early spring came between these same extremes.) 
The frequency curve to represent this is a fairly regular one, showing the greatest 
number at a length of 3-2, although nearly as many at 3-4 and 3-6. The growth for 
the second year varies from 7-5 to 14-4, with an average of 11-1. The greatest number 
came at 10-7 and 11-6. Although the base of the curve is much more spread out 
than in the first-year curve, the regularity is much the same. The length at the end 
1 Chamberlain, F. M. Observations on salmon and trout in Alaska. Bureau of Fisheries 
Document No. 627, 1907. 
