FISHWAY SLOPE AND FISHWAY LENGTH 



Initial experiments comparing the performance 

 of salmonids in fishways with slopes of 1 on 8 and 

 1 on 16 indicated a higher rate of passage in the 

 steeper slope fishvvay. However, the tests were 

 conducted in short segments of fishways and the 

 possibility that the increased rate was the result of 

 turbulence and lack of resting area had to be con- 

 sidered. To make a further comparison of the 



Figure 1 1 . — Biolosist extracting a sample of blood 

 from a fish exercised in one of tfie endless fishways. 

 Blood samples were analyzed for lactate and 

 inorganic phospliate to determine if the fish was 

 fatigued. 



eflfect of slope upon rates of fish movement and to 

 measure the effect of length of fishway on fish per- 

 formance, experiments were undertaken using a 

 pair of "endless" fishways with slopes of 1 on 8 

 and 1 on 16. These endless fishways (figs. 8 and 9) 

 were pooj-and-overfall fishways constructed so 

 that each made a complete circuit (fig. 10), with 

 the highest pool connected to the lowest pool by 

 means of a lock. When a test fish had ascended 

 to the top of one of these fishwaj's, it was rapidly 

 lowered by lock to the lowest pool to ascend again. 

 By repeating this procedure, fishways of any 

 desired length could be simulated. Comparisons 

 were made on the basis of fish performance and 

 also on the basis of biochemical indices of fatigue 

 such as lactate and inorganic phosphate of the 

 blood (fig. 11) and muscle. 



No evidence of fatigue was found in either fish- 

 way when the proper pool flow conditions pre- 

 vailed. Blood lactates, the most sensitive of the 

 biochemical measurements, showed (fig. 12) a 

 moderate increase (lactate levels above 125 mg. 

 percent may be lethal to fish under certain circum- 

 stances) during active ascent and were back to the 

 control level in both fishwaj's within 1 hour. Most 

 of the fish were tested with an ascent of approx- 

 imately 100 pools. However, a limited number 

 were permitted to make extended ascents exceed- 

 ing several hundred pools and at least four of each 

 species were allowed to ascend more than 1,000 

 pools. One blueback salmon was permitted to 

 ascend for over 5 days, climbing continuoush" over 

 6,600 pools before the test was terminated. This 

 was a vertical ascent of more than a mile in a 

 l-on-8-slope fishway. The conclusion drawn is 

 that ascent of a properly designed fishway is only 

 a moderate exercise for the fish, possibly similar to 

 swimming at a "cruising" speed that can be 

 maintained over long periods of time. 



The exaggerated pattern of work-and-rest that 

 appeared in the l-on-8 endless fishway resulted in 

 the fish spending about 70 percent of the time 

 resting in the turn pools (fig. 13). In an actual 

 fishway this would result in about 70 percent of 

 the fish being in resting pools at any given time. 

 To avoid this impractical condition, the hydraulic 

 pattern in the l-on-8 fishway was changed by 

 modifying the weirs. This changed the pattern 

 of movement so that the fish rested in each pool 

 (fig. 14), clearl^v demonstrating the importance of 

 pool flow pattern to fishway design. The steeper 



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