Fishery bulletin of the Fish and Wildlife Service - NOAA

242 SALMON OF THE KABLTJK KIVEB, ALASKA
on the day of capture. Each scale sample contains scales from about 100 fish, these
fish being taken at random from the day's catch. The scales are cleaned, mounted
in sodium silicate between glass slides, examined under a microscope, and the age of
the fish in the sample determined.
A preliminary study of the age-group composition of the various samples showed
that the composition of the run changes throughout a season, and consequently it
was found advisable to divide the season into a series of short successive periods of
time. For the purpose of comparison these units of tune should begin and end on the
same dates each year, and so the scale samples, escapements, and runs have been
grouped in 7-day periods which coincide from year to year.
Tables 3 to 16 give the age-group analyses of the several weekly samples taken in
1922, and in the years 1924 to 1936, inclusive. It will be seen from these tables that
the age-group composition of the run changes considerably during the season, and
also that the percentage occurrence of any one age group varies from year to year.
In considering the three principal age groups, 5 3, 63, and 64, it will be noted that
5 3 usually is the dominant age group present in the run. The percentage occurrence
of the 6 8 age group always decreases as the season progresses, this age group never
being important toward the end of the run. The percentage occurrence of the 64 age
group generally increases as the season progresses. This age group, while seldom of
importance in the early part of the season, usually is quite important in the latter
part of the season.
The data included in tables 3 to 16 are of further value in that they are essential
in calculating the percentage occurrence of the various age groups in the yearly
escapements and hi the returns from these escapements as given in tables 18 and 25,
respectively. Since the salmon returning to Karluk each year from each of the
previous spawning populations, or escapements, can be segregated according to age,
the data in tables 3 to 16 are likewise essential in calculating the returns from known
escapements. These returns are given in table 20.
TABLE 3.—Percentage occurrence of each age group, during week, in the Karluk red-salmon run of
19SS, determined by analyses of scale samples collected from a total of 8,469 fish
June 21
June28
Julys
July 12
July 19
July 26
Aug. 2
Aug. 9
Aug. 16
Aug. 23
Aug. 30
Sept 6
Sept. 13
Sept. 20 . ...
4,
0.7
.7
.6
4j
0.7
.7
.7
.6
.6
.7
.7
1.3
1.4
.7
.6
2.0
4l
2.2
.6
1.3
.7
.7
.7
2.7
2.7
4i
0.7
1.4
61
1.4
2.1
.7
1.3
fil
Age groups
31 0
34.4
36.1
32.3
37.3
36.0
62.0
76.0
69 3
72.0
87.2
85.3
77.0
80.1
91.1
87.8
5,
1.3
.9
.7
2.7
.7
.7
.7
.7
2.0
3.3
2.1
2.0
Si
0.7
6i
66 в
60.7
68.7
60.3
56.0
61.3
26.7
18.0
21.3
16.6
8.7
6.7
2.7
3.3
1 4
1.4
6,
1.4
1.9
3.0
6.3
10.0
8.7
4.0
8.0
8.7
2.0
6.0
16.2
11.2
2 1
2.0
6j
0.7
7 4
0.7
.7
.7
.7