Fishery bulletin of the Fish and Wildlife Service - NOAA

SALMON RUNS OP THE COLUMBIA RIVER IN 1938 115
it to be justified here. This gives the following estimated weights: For the week
ending April 30, 12.20 pounds; April 23, 10.42; September 3, 25.60; September 10,
25.05; September 17, 24.50; September 24, 23.95; October 1, 23.40; October 8, 22.85;
October 15, 22.30; October 22, 21.75; October 29, 21.20; and for the week ending
November 5, 20.65. After this date so few fish were taken in the fishery that an
approximation on the basis of about 20 pounds is adequate for all purposes.
TABLE 11.—Estimated weights of chinook salmon in the commercial catch in Zones 1 and S for the
spring season of 1939. Figures for the first S weeks were extrapolated
Week ending
May 7
May 14
May 21
May 28
Estimated
mean
weight
(13 08)
(16 76)
(17 54)
19 32
Week ending
June 11
June 18
June 25
Estimated
mean
weight
21.10
22.88
24.66
26.44
Week ending
July 2
July 9
July 16
July 23
July 30
Estimated
mean
weight
28.22
30.00
29.46
28.90
28.35
Week ending
A
Aug 13
Aug. 20
Aug. 27
Estimated
mean
weight
In converting poundage of silver and chum salmon to numbers of fish we here
adopt an average weight of 10 pounds for both species—the same as that adopted for
steelhead trout. This is not in accord with the figures commonly given, viz, 7-9
pounds for silvers and 8-10 pounds for chums. Some years ago, however, the writer
measured and weighed several hundred silver and chum salmon taken on the lower
Columbia River, and these gave averages for both species that were considerably over
10 pounds—240 chums averaged 10.3 pounds with á standard deviation of 2.0, and
133 silver salmon averaged 10.9 pounds with a standard deviation of 2.6. This average
does not include 16 silver salmon grilse which were in the same collections. The
samples came from fish caught in traps and the'small grilse are seldom taken by gill
nets although, as stated above, this form of gear is of primary importance in the
Columbia River fishery. In view of these figures, and the purpose to which the estimates
are to be put, it seems reasonable to use a conversion factor of 10 pounds
for both of these species. 7
Some time is required for the journey of the fish up the river, so that on a given
day the fish in the upper river may be expected to represent an entirely different stock
from that to be found simultaneously in the lower river, although it is the same stock
as was to be found in the lower river during an earlier period. Therefore, in order to
aid interpretation of some of the more important data, these have been presented so
that as nearly as possible those referring to the same stocks of fish are placed on the
same lines in the table. In other words, the several series of data have been so "lagged"
that comparable portions are related to the same marginal date—which date is the
end of the week in which the fish may reasonably be expected to have entered the
rrver from the ocean. From a careful examination of tables 1 to 5 it appears that a
given group of fish that entered the river and were to be found in Zones 1 and 2 in a
given week (the week of the marginal date in the table) would be in Zones 3 to 5 the
next week, at Bonneville and in Zone 6 during the second week, and at Rock Island the
fourth week after their appearance in Zones 1 and 2.
In table 12 the dates given in the left-hand margin are those ending the weeks
during which the fish were in Zones 1 and 2, the estimated catches made in Zones 3 to 5
' Since this report went to press a paper by Wilbert Chapman, of the Washington State Department of Fisheries, dealing with
the weights of fish taken in the Columbia River fisheries has appeared. His figures are somewhat different from ours but it is not
possible to give a critical discussion of them here,
27 80
27.25
26.70
26.15