40 



20 



Slreoming Flow 

 ^Developed 



rin ^n |"EDIAN( 



22'26) 



I40r 



120- 



100 



g 80 



60 



40 



20- 



MEOIAN 



(5U8) 



u^raj\ 



i-JLrw^ n n-TS.ri,, 



20 30 40 



Minutes offer Release 



50 



60 



FIGURE 9. --COMPARISON OF FISH PASSAGE AT UPPER AND 

 LOWER WEIRS OF FISHWAY IN THE JULY 5, 1956 CAPA- 

 CITY TEST. STREAMING FLOW DEVELOPED AT UPPER 

 WEIR (60) AT END OF MINUTE 3. PLUNGING FLOW IN 

 EFFECT DURING ENTIRE 60-MINUTE PERIOD AT LOWER 

 WEIR (54) . 



60-minute test period. By contrast, the 

 passage curve at weir 60 is clearly bimodal. 

 The abrupt decline in numbers passing per 

 unit time directly coincides with the incep- 

 tion of streeiming flow at this weir. 



In measuring the possible effect of 

 strccuning flow on rate of movement, we may 

 exajnine the position of the median psissage 

 time at the two weirs (54 and 60). At the 

 lower weir (54) half of the group had 

 entered the fishway in approximately 5.3 

 minutes (figure 9) while half had ascended 

 the fishway at 22.4 minutes aifter the start 

 of the test. Thus, the median elapsed time 

 in the fishway was 17.1 minutes (22.4- 5.3). 

 Conceivcibly, had streaming flow failed to 

 develop at weir 60, the medicin time at this 

 weir might have been reached several min- 

 utes earlier with a resultant decrease in 

 the median elapsed time. This is based on 

 the assumption that all passage to the right 

 of minute 9 would be proportionately reposi- 

 tioned to the left, filling in the depres- 

 sion in the passage curve caused by stream- 

 ing flow. 



Comparison of the capacity trials held 

 on July 2 and 5 (table 1) gives interesting 

 support to the above. These trials were 

 virtually identical as regards species com- 

 position. A principal difference in the 

 tests is that streaming flows did not devel- 

 op in the July 2 trial. Significantly, the 

 median elapsed time for the July 5 trial 

 (streaming flows in effect) was approximately 

 4.5 minutes in excess of that observed in 

 the July 2 test (17.1-12.6). 



Examination of Entry Rate 

 into Fishway 



One of the means by which we expected 

 to recognize whether capacity were reached 

 or exceeded was to examine the entry rate — ' 

 into the fishway. Conceivably a peak entry 

 rate (the maximum number of a given size 

 which could enter a fishway 6 feet wide in 

 unit time) would be reached, and provided 

 that the supply could be maintained at this 

 point, we would expect the net entry to 

 stablize at a given level (assuming fish 

 size remained constant). During the first 

 seven experiments (May 22 to July 13 



6/ 



The striking feature in the passage of 

 fish at weir 60 is that movement was virtu- 

 ally halted for approximately 5 minutes 

 (minute 4 through 8) during the initial 

 period that streaiming flow was in effect. 

 (See table 2 in the Appendix.) Thereafter, 

 the migrcints apparently gradually became 

 conditioned to the change in flow and con- 

 tinued their ascent out of the fishway. 



_6/ As applied here, the entry rate is net 

 entry per minute; i.e., the total number 

 of fish entering a pool in a given min- 

 ute minus the number of fish dropping 

 downstream out of the pool in the same 

 minute. A subsequent section will be 

 devoted to "fallbacks" which we have 

 termed those fish which move downstream 

 from one pool to another. 



13 



