Fishery bulletin of the Fish and Wildlife Service - NOAA

FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 259
would produce a surplus of only 1,000,000» It is then of considerable importance to
determine, for each given area, the size of the escapement which will consistently
produce the greatest surplus.
In figure 4 the return minus escapement, or surplus, has been plotted against the
escapement. A negative correlation between escapement and surplus is indicated,
and it appears that, overlooking the return from the fall escapement of 1921, the
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FIQUBE 3.— Beturns from the spring and fall escapements for the yean 1921 to 1929, Inclusive.
optimum escapement for the spring and fall runs was approximately 200,000 fish for
each period or a total yearly escapement of 400,000 fish. There are several facts,
however, that should be considered before drawing conclusions from the data. The
escapement of 1921, and. especially the fall escapement, produced a very good surplus.
The Karluk pink salmon spawning population of 1922 produced an exceptionally large
surplus, as did the red salmon spawning population of that year, indicating unusually
favorable environmental conditions. Conditions on the spawning grounds were
judged to be very unfavorable during 1924 and 1926, and hence the returns from those
escapements were likely much lower than if the environment had been normal.
Furthermore, only the escapement of 1921 (1,500,000 fish) produced a surplus comparable
to the average catch made during the 20-year period from 1888 to 1907. While
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