Fishery bulletin of the Fish and Wildlife Service - NOAA

SALMON RUNS OP THE COLUMBIA RIVER IN 1938 117
river above Bonneville, this will tend to magnify the importance of the spawning in
the river above Bonneville, including that above Rock Island. Undoubtedly a part
of the commercial catch of all species except the blueback is composed of fish derived
from the tributaries below Bonneville, but it seems probable that this forms a relatively
small part of the total catch of chinook salmon, at least until after the peak of the fall
run. There is a very large count of chinooks at Bonneville immediately after the
beginning of the closed period in August—certain evidence that a large proportion
of the fish that are in the river at that time
are derived from populations spawning
in the higher tributaries. On the whole we
feel fairly confident that only a relatively
small part of the commercial catch of this
important species that is made before the
first of October comes from the runs into
tributaries below Bonneville.
An understanding of the analysis of
these runs, particularly in relation to the
fish destined to spawn in the upper Columbia
River above Rock Island Dam, may
be aided by the following discussion (see
also fig. 2). 8 While this particular treatment
is related specifically to the run to
Rock Island, a similar treatment could be
applied to any other tributary runs for
which similar data were available.
Let us assume:
A. That the estimated escapement at
Celilo is the total escapement for the total
run of the period ; and
B. That the ratio between the escape-
ment at Rock Island Dam and the catch
made from the same stocks of fish
that furnished this escapement is the
same as that between the escapement
at Celilo and the total catch. This
assumes that there is no appreciable
loss between Celilo and Rock Island,
and that, for each species, the proportion
of Rock Island fish caught is the same as the average.: for all salmon of the species
that are passing through the fishery at the same time.
From this it would follow also that the relation between the escapement at Rock
Island Dam and the run referable to this escapement will be the same as that between
the escapement at Celilo and the total run.
Having then determined, for a selected tune interval, the total catch, denoted
by C, the escapement at Celilo, denoted by EI, and the count at Rock island, denoted
by EZ, we are able to determine the following:
> This clarifying symbolic treatment was contributed to the original report of the Board of Consultants by Dr. Durand, who
has kindly permitted slightly altered repetition here.
449668—42 3
FIGURE 2.—Diagram of the ultimate subdivisions of the
main run of Chinook salmon entering the Columbia River,
illustrating the various ratlos. B denotes total run; Ci
denotes total catch below Bonneville Dam; BC denotes
Bonneville count; Ci denotes catch above Bonneville
Dam; Ei denotes escapement at upper limit of commercial
ashing; Ei denotes escapement at Rock Island Dam; ?
denotes diversions of unknown amounts at various points
ta the river.