146 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



months of June to September. There are 5 modes: minor ones about the end of 

 March, the first of May, and the first of December, and major modes early in July 

 and about the middle of August. The run of silver salmon extends from early in 

 August to the end of the year, but centers rather broadly from the middle of September 

 to the middle of October. The chum sahnon run attains a well marked maximum 

 about the first week in November, but extends from about the first of October to about 

 the middle of December. 



4. The main parts of the chinook, blueback, and steelhead runs spawn above 

 Bonneville, but silvers and chums spawn chiefly in the tributaries below the dam. 



5. There is some evidence of error in the identification of species in the Bonne- 

 ville count. 



6. The importance of the runs to the river above Rock Island (largely affected 

 by the dam at Grand Coulee) is shown by the ratio of the Rock Island count to the 

 estimated escapement. Some 4 percent of the very early chinooks passing Bonneville 

 previous to the first of May appear later at Rock Island. Of the May run of this 

 species, about 6 percent apparently went to this portion of the river. Of the June- 

 July run, which is poor and apparently seriously depleted, some 15 percent is attrib- 

 utable to these races. During the remainder of the year only about 1 percent of 

 the estimated escapement appeared here. Approximately 40 percent of the blueback 

 run spawns above Rock Island. In the case of the steelheads, the early and late runs 

 contain 10 percent or more of fish spawning above Rock Island; but during the main 

 portion of the run, June through September, only about 1 percent of these fish go to 

 this portion of the river. 



7. The intensity of the fishery for chinooks, bluebacks, and steelheads is 

 measured by the ratio of the commercial catch to the escapement, as calculated from 

 the data given in the modified tables. For the May run of chinooks it is shown that 

 only about 1 fish out of 7 escapes the commercial fishery and is available for the future 

 maintenance of this run. During June and July, a period of great scarcity, only 

 about 1 fish in 6 escapes, and during the remainder of the run, August through Decem- 

 ber, the escapement is considerably better but even at this time about twice as many 

 fish are taken in the commercial fishery as remain to reproduce. These figures do 

 not take into consideration the effect of the intensive oceanic fishery which would 

 materially increase the catch-escapement ratio. In the case of the blueback salmon 

 the ratio of catch to escapement is approximately 4:1, indicating that only about 

 1 fish out of 5 of this species escapes the fishery. The ratio for the steelheads varies 

 with the season, but for the main part of the run, June to September, it is somewhat 

 greater than 2:1 ; i. e., more than 2 out of 3 steelheads are taken in the fishery. Similar 

 ratios for the silvers and chums cannot be determined because few fish of these species 

 pass Bonneville; consequently no estimate of the net escapement can be made. 



8. The weekly closed period, 6 p. m. Saturday to 6 p. m. Sunday, in force during 

 the spring fishing season, May 1 to August 25, is almost entirely ineffective insofar 

 as it may tend to increase the number of breeding fish on the spawning grounds. 

 Its chief effect is to spread the fishing over a longer stretch of the river. This is the 

 result of an intensive fishery conducted over a long area. The closed season from 

 August 25 to September 10 is designed to protect the peak of the chinook run and a 

 portion of the steelhead run, but it acts, in a larger way, much the same as does the 

 weekly closed period in that it chiefly tends to extend the fishing areas. The effect 

 of an increased escapement of fish through the fishing area below Bonneville is almost 



