where the chronological order of the arrival of 

 tagged fish could not be determined. At Turn- 

 water Dam, moreover, migrating chinooks were 

 subject to delay, and conclusive data of the 

 time-out period for fish from the different tagging 

 areas were not obtained. The days-out at 

 Tumwater Dam for individual chinooks ranged 

 from 11 to 65 days, and there was no evidence 

 that any one group of releases was different from 

 another group. 



RETURNS AT ROCK ISLAND 



Sockeye 



As hypothesized previously, the difference 

 in days-out at upstream points between above- 

 and below-dam releases should equal the days-out 

 period at Rock Island Dam of below-dam releases. 

 The results at Rock Island Dam (fig. 13) confirm 

 the hypothesis. The majority of fish passed 

 through the fishways within 2 to 4 days after 

 being released below the dam. In 1953, the peak 

 of the days-out curve occurred a day earlier 

 than in 1954-56. This may have been because 

 the majority of fish in 1953 were tagged during 

 a 3-day period near the end of the run in contrast 

 to the season-long tagging of the later years. 



The comparisons of days-out by area of release 

 at Rock Island are shown in figures 14, 15, and 16. 

 At first glance we have a fairly consistent picture 

 of passage from the two areas of release, with the 

 exception of the right bank releases in 1956. A 

 better comparison of the days-out period for 

 each release area is gained from the following 



RIGHT BANK BELOW 



- Left ladder 

 Center lodder 

 Right ladder 



I n. ire 13. — Comparison of days-out at Rock Island of 

 tagged sockeye released below the dam, 1953-56. 



I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 IG 17 18 19 20 21 22 23 24 25 26 

 DAYS-OUT 



Figure 14. — Days-out of tagged sockeye at Rock Island 

 for each area of release expressed in percentages of 

 total observations by ladder, 1954. 



array of modal values of days-out for each tag 

 release area and the ladder of passage (table 17). 



In 1954, right bank releases took a day longer 

 to pass at each ladder than the left bank tag 

 releases. This difference was not noted for 

 other years except in 1955, in the center ladder. 

 In 1956, right bank releases passed sooner than 

 left bank releases. The 1956 tagged fish, it is 

 recalled, were released off the face of the dam close 

 to the fishways. Apparently the few sockeye 

 using the right ladder moved into the ladder 

 immediately after tagging and the remainder 

 moved downstream or across the river. Those 

 sockeye using the right ladder possibly moved up 

 sooner upon finding the ladder because of the 

 absence of resting areas below the ladder. 



Measuring the number of days-out for tagged 

 salmon at Rock Island Dam depended on the 

 ability of the counters to distinguish the kinds 

 and colors of tags used. As previously pointed 

 out, the counters made many errors. To test if 

 the counters were approximately correct in identi- 



360 



U.S. FISH AND WILDLIFE SERVICE 



