FISHERY BULLETIN: VOL. 70, NO. I 



Table 5. — Numbers of 

 mean travel times of 



sockeye salmon that were tagged, released below Rock Island Dam and the numbers, and 

 tagged fish that were later observed passing over the dam's fish ladders, 1964 and 1965. 



1 The total number observed may exceed the number tagged. See text (p. 132) for explanation. 



percentage varied from 40.1 to 62.8 in 1964 and 

 from 44.2 to 61.8 in 1965. For chinook salmon, 

 the range was 61.5 to 69.0 ''r in 1965, the only 

 year in which adequate data were obtained. 



Travel Time from Release to Observation in 

 Fish Ladders 



Travel time by date of release, release location, 

 and ladder for the 1964 and 1965 experiments 

 are presented in Table 5. Following analysis of 

 the 1964 data, we will examine the 1965 exper- 

 iments (p. 135). 



Analysis of variance tests of the hypothesis of 

 no difference in travel time between left- and 

 right-bank releases (all ladders combined) are 

 given in Table 6. Because there were no re- 

 leases from the right bank in period IV, the test 

 compares the two left-bank releases. Within- 

 release group variances were pooled to form an 

 overall pooled estimate of the variance with 883 

 degrees of freedom. Because the mean travel 

 times did not differ significantly between the 



Table 6. — Analysis of variance tests of the hypothesis 

 that sockeye salmon, tagged and released on the left bank 

 below Rock Island Dam in 1964, traveled over the Rock 

 Island Dam fish ladders equally as fast as fish released 

 on the right bank; the testing period IV involves two 

 left-bank releases. 



Period 



Release locations 

 compared 



Mean travel time in 



half-days, 

 all ladders combined 



f-stotisticsi 

 (1 and 883 df) 



1 «♦ = Highly significant at the 0.01 level, reject hypothesis of equal 

 travel times, and conclude that travel time was significantly less for fish 

 released from one bank than for those released on the other bank. 



N.S. = Not significant at the 0.05 level, accept hypothesis of equal 

 travel times. 



July 15 and 16 left-bank releases, these releases 

 were combined. The July 21 and 23 right-bank 

 releases were similarly tested and combined. 

 Note that in periods I to III, travel times for the 

 left-bank releases were significantly less than 



134 



