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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O 3 6 9 12 15 



ESCAPEMENT 

 (in hundreds of thousands) 



Figure 3.— Returns from the spring and fall escapements for the years 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. Tlie 

 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 hkely much lower than if the environment had been normal. 

 Furthermore, only the escapement of 1921 (1,500,000 fish) produced a surplus compa- 

 rable to the average catch made during the 20-year period from 1888 to 1907. While 



527715 — 43 4 



