FISHERY BULLETIN: VOL. 70, NO. 1 



Table 8. — Analysis of variance tests of the hypothesis 

 that sockeye salmon, tagged and released on the left bank 

 below Rock Island Dam in 1965, traveled over the Rock 

 Island Dam fish ladders equally as fast as fish released 

 on the right bank. 



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



travel times. , . , i i ^■ 



* = Significant at the 0.05 level, reject hypothesis of equal travel times, 

 and conclude that travel time for fish released on one bank was signifi- 

 cantly less than for fish released on the other bank. 



•* = Significant at the 0.01 level, reject hypothesis, and conclude as 

 above. 



site in period I but not significantly so. In peri- 

 ods II and III, fish released on the right bank 

 moved over the dam significantly faster than 

 their left-bank counterparts. In periods IV and 

 V, statistically significant differences were found 

 only in the other direction, e.g., left-bank re- 

 leases were faster than right-bank releases. 



Thus, there is no clear superiority of one re- 

 lease location over the other. The effect of re- 

 lease location on relative and absolute travel 

 times changed from period to period. In con- 

 trast, tagged sockeye salmon released from the 

 left-bank site in 1964, before the spill was in- 

 tentionally modified, moved past the dam faster 

 than their right-bank counterparts. The main 



difference between the 2 years seems to be the 

 decreased jiassage time for the right-bank re- 

 leases of 1965 which, for every comparable peri- 

 od, moved over the dam faster than their 1964 

 counterparts. 



Overall travel times (3.6 half-days in 1964 and 

 3.2 half-days in 1965) did not differ significantly 

 despite the better performance by the right-bank 

 releases. 



Next, it is appropriate to examine the effect 

 of ladder choice on mean travel time in 1965 

 by period and with release areas pooled. The 

 basic data and the corresponding tests of sig- 

 nificance are given in Table 9. No significant 

 differences were found. Ladder choice did not 

 appear to influence travel time. The same re- 

 sult was noted in 1964. 



SPILL PATTERN MANIPULATION 



On August 3, 4, and 5, 1964, spill was shifted 

 from gates adjacent to the center ladder to the 

 gate on the far right side of the dam. During 

 this 3-day period, two groups of tagged fish (Au- 

 gust 3 and 5) were released from the left bank 

 and one (August 4) from the right bank. We 

 will consider the left-bank releases first. The re- 

 lease of August 3 was subjected to 3 days of 

 the modified spill condition, whereas the release 

 of August 5 was subjected to 1 day of the same 

 condition. The left-bank release of July 31 pro- 

 vided a crude "control" (no eflfect of modified 



Table 9.— Analysis of variance tests of the hypothesis that sockeye salmon, tagged 

 and released below Rock Island Dam in 1965, traveled over the right fish ladder at Rock 

 Island Dam equally as fast as those using the left and center ladders. 



Period 



Ladders 



compared 



Mean travel time in half-days, 

 release areas combined 



Lefl 

 ladder 



Center 

 ladder 



Right 

 ladder 



/"-statistics^ 



Degrees 



of 

 freedom 



2.906 



3.577 



2.340 



3.464 



3.201 



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



136 



