SALMON RUNS OF THE COLUMBIA RIVER IN 1938 141 



fish that form the second of the two major peaks — roughly those that enter the 

 river during the months of August and September. The count at the Bonneville 

 Dam during these months was over twice that of the preceding 2 months, during 

 which the first of the 2 major peaks appeared. A more complete examination of the 

 data in table 22, however, shows that this improvement in the Bonneville count is 

 by no means indicative of a corresponding improvement in the net escapement because 

 the intensive fishery above Bonneville during September and October takes such a 

 large number of steelheads that the actual escapement past the upper end of the 

 fishing district is, relatively, not much greater than in the preceding period. The 

 ratio of total catch to net escapement during June and July is 2.57:1, and during 

 August and September is 2.16:1. (Both catch and escapement figures are, of course, 

 estimates, and the periods of time are to be referred to the marginal dates of table 22.) 

 It is to be noted that these ratios are considerably higher than 1.65:1, which was the 

 figure given in the original report for the months of June, July, and August. The 

 difference is obviously due to the fact that the data now available are much more 

 complete, containing those for the last half of the main run as well as for the first half. 



The steelhead run of the final period to be considered, from September 25 to 

 the end of the year, is much less important than that of the two periods just con- 

 sidered and is characterized particularly by the relatively slight importance of the 

 part of the run that passes Bonneville. The total count at Bonneville was only 1,552 

 steelhead trout, and the catch in the river below the dam was nearly 10 times as 

 great. It is clearly indicated that the steelheads spawning in the tributaries below 

 Bonneville form a much larger part of the late fall run than of those entering the 

 river previous to September 25. Of the steelheads that do pass Bonneville, however, 

 the data appear to show that a relatively large percentage spawn in the Columbia 

 above Rock Island. 



The last column of table 24 shows the percentages of Rock Island fish in the 

 estimated escapement to the river above Celilo Falls for each of the selected periods. 

 The percentage of Rock Island fish in the run up to April 16 was a little over 5; for 

 the period ending May 28 was over 10 percent; for the period ending July 30 and 

 including the first major mode, only 1 percent; for the period of the second major 

 mode, ending September 24, 1.7 percent; but for the late fall period it was nearly 14 

 percent. Although the figures are not particularly reliable on account of the rela- 

 tively few fish involved, it is interesting to note the indication of greater importance 

 of the upper Columbia races in the late fall and whiter runs and also in the early 

 spring runs. These data at least indicate that a relatively large percentage of those 

 steelheads that pass Bonneville during fall and winter spawn in the main Columbia 

 River and its tributaries above Rock Island Dam, and that the Rock Island contin- 

 gent in the main part of the steelhead run is, both absolutely and relatively, of much 

 less importance than in fall and early spring months. 



These data also provide some evidence that a larger proportion of late fall fish — 

 entering the river after the first of October — spawn in tributaries below Bonneville. 

 This is shown by the ratios of the catch below Bonneville to the Bonneville count 

 for the different parts of the year (table 24). For the first part of the run to be 

 affected by the commercial fishery, April 17 to May 28, this ratio was 0.291:1 — only 

 about one-fourth of the fish entering the river were taken below the dam. During 

 the June and July run the ratio was 2.2 :1. During the next 2 months, influenced by 

 the closed period, it dropped to approximately 0.8:1. During the last 3 months of 



