Time of Year and 

 Intensity of Migration 



Young salmonoids were taken throughout 

 the trapping period at Tumwater Dam, from 

 April to November. They were caught from 

 the time trapping was initiated April 19 of 

 1955 and April 2 of 1956, and presumably 

 may have started their seasonal migration 

 at an earlier date. The spring migration 

 of blueback and chinook salmon reached its 

 peak in early May, prior to the high water 

 period of the spring run-off season. No 

 knowledge was gained of the extent of migra- 

 tion during the spring flood season occur- 

 ring in late May and June. However, as 

 young fish were taken immediately prior to 

 and following the high water period, it is 

 to be expected that some migration was 

 occurring throughout this period. Large 

 numbers of chinook and steelhead trout were 



10,000 



trapped during summer and fall months. 

 Peaks in abundance of steelhead trout were 

 noted in September. Young salmonoids were 

 taken as late as mid-November when winter 

 icing conditions forced cessation of trap- 

 ping. Thus, we find young fish migrating 

 during at least eight months of the year at 

 Tumwater Dam on the Wenatchee River. 



Blueback salmon . --The spring migration 

 of blueback salmon f inger lings for 1955 as 

 determined from evening counts is given in 

 figure 11. It is apparent that migration 

 of bluebacks commenced some time prior to 

 April 19, the first day of trapping. It is 

 not known whether the various peaks of abun- 

 dance are a characteristic of the downstream 

 movement or due to conditions at the dam. 

 In 1956, figure 12, the pattern is much the 

 same although fewer fish were taken this 

 season. The reason that so few fish were 

 taken was attributed to the much greater 

 flows existing at that time. Apparently, 

 comparatively few fish were attracted to- 

 ward the intake tube. The peak occurred on 



300 



280 



260 



240 



220 



200 



^ 180 

 u. 



u. 160 ■ 

 o 



S 140 



CD 



£ 



= 120 



z 



100 

 80 

 60- 

 40 

 20 

 



X 



20 22 24 26 28 30 2 4 6 8 10 12 14 16 

 APRIL MAY 



Figure 11. --Downstream migration -blueback 

 salmon. Tumwater Dam, 1955. Counts 

 from 7 p.m. to 12 midnight. 



Figure 12. --Downstreajm migration - blueback 

 salmon. Tinnwater Dam, 1956. Counts 

 from 7 P-ni. to 12 midnight. 



10 



