Fishery bulletin of the Fish and Wildlife Service - NOAA

FISHERY BULLETIN OF THE FISH AND WILDLIFE BEBVICE 255
measure, for the minor fluctuations in the time of appearance of the runs from year
to year and may be the cause of bimodality in the runs. Regardless of the primary
cause of this phenomenon, it would seem that there are two self-perpetuating components
of the red-salmon population in the watershed, and that each should be given
adequate protection.
During the 16 years under consideration the spring runs have ranged from 303,000
fish in 1922 to 1,715,000 fish in 1926, the average being 817,000 fish. The fall runs
have ranged from 652,000 fish in 1929 to 3,205,000 fish in 1926, the average being
1,211,000 fish. The total run has-ranged from 1,058,000 fish in 1922 to 4,920,000
fish in 1926, the average being 2,028,000 fish. Thus, there has been a rather wide
range in the number of fish in thé runs from year to year, and the average run has been
far below that of the early days of the fishery when for a period of 7 years the catch
alone exceeded the run (catch plus escapement) during this period by more than
1,000,000 fish per year.
RETURNS FROM KNOWN SPAWNING POPULATIONS
In order to maintain the salmon runs at a high level, an adequate escapement
must be obtained for each and every suitable spawning area. The question at once
arises as to what constitutes an adequate escapement. This question has confronted
the salmon conservationist since the first attempt was made to regulate a fishery, and
it is a question that still needs considerable study. Each small section of a spawning
area must have its proper escapement, and in the final analysis, it is necessary to
determine, for each small area, the size of an adequate spawning population. The
problem is further complicated because an adequate spawning population for a given
spawning area is not necessarily constant. Variations in meteorological conditions
result in changes in environmental conditions on the spawning grounds during the
spawning and incubation periods from year to year, consequently, a spawning escapement
which may be adequate in one year may be inadequate, or may be more than
adequate, in some other year. As there is no means of predicting what meteorological
conditions will prevail during the spawning season and the subsequent incubation
period, we can at best determine an average figure for the optimum size of the spawning
population for each spawning area.
Most of the progeny from a year's spawning population of Karluk red salmon
return as adults in their fourth to seventh year. 8 In order to determine the return
from the spawning of 1930, for example, it is necessary to determine the number of
4-year fish in the run of 1934, the number of 5-year fish in the run of 1935, the number
of 6-year fish hi the run of 1936, and the number of 7-year fish in the run of 1937.
The numbers of these several groups are then added together to determine the total
return from the spawning of 1930. The returns from the escapements of the spring
run, from the fall run, and from the total run of each year are given in table 20.
The escapement of 1921 (1,500,000 fish) produced a very good return both in фе
ratio of return to escapement and also hi the total number of fish produced. While the
return from the spring escapement was good, the return from the fall escapement was
much better and was largely responsible for the exceptionally good total return.
• There are a few 8-year and 8-year Bah In tue Karluk runs whicb are Included In tfoe tabulations, bet their presence Is quite
unimportant.