106 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



The catch within the river does not, therefore, represent the entire productivity of the 

 runs of this species, but with available data it is not possible to determine with much 

 accuracy what this total productivity actually is. The constant decline of the last 20 

 years, however, taken in connection with data presented in this report, certainly 

 warrants the conclusion that the chinook runs are seriously depleted. 6 We shall show 

 below that the present exploitation of these depleted ruus is being conducted with an 

 intensity so great that it can only lead to disaster in the not far distant future unless 

 the present trends can be altered. 



The blueback salmon catch for both of the first 2 periods shown in figure 1 is ap- 

 proximately twice that of the succeeding periods, and there is some reason to think 

 that the abundance of blueback salmon previous to 1890 was at least the equal of that 



T 



T 



CHINOOK 

 BLUEBACK 

 STEEL HE AD 



SILVER 



CHUM 











J L 





J I I L 



'80 '85 '90 '95 1900 '05 



'10 



'15 '20 '25 



30 35 



40 



Figure 1.— Average annual catch by 5-year periods of Chinook salmon, 1866-1938; and of blueback, silver, and chum salmon; 



and steelhead trout, 1891-1938. 



which existed during the decade of the 90's. Since 1900, however, there has been 

 little change — the trend is almost horizontal. These facts imply that this species 

 originally was fairly abundant in the Columbia River, but that this early abundance 

 was sharply reduced about 1900, and since that time there has been comparatively 

 little change. This species almost universally spawns in or above lakes and it seems 

 quite possible that the damming of lakes for use as reservoirs without providing 

 adequate fishways, and the unrestricted use of unscreened irrigation ditches, were 

 chiefly responsible for the depletion. 



In figure 1 considerable fluctuation is shown in the estimated catch of steelbead 

 trout, especially in the early years of the record, but there is little evidence of a marked 



• Since this report was in page proof an additional study of these data has been made using the methods of the control chart as 

 developed by Shewhart, Demlng, and others, for the control of quality in manufactured products. The results show conclusively 

 that the productivity of the chinook fishery since 1925 has been at a distinctly lower level than was maintained during the period 

 1876 to 1920. These will be published elsewhere. 



