When flow3 were uniform, evidence of interrupted 

 passage of fish was lacking. When hydrauhc 

 jumps were estabHshed in the channel a number 

 of fish were observed to linger in the low-velocity 

 areas created by these jumps. Occasionally fish 

 remained in these areas for several minutes 

 before continuing their movement tlirough the 

 channel. Improper design and operation of 

 diflfusion chambers conceivably may create similar 

 disturbances in the flows of collection and entrance 

 channels, giving rise to delays in fish movement 

 comparable to those occasioned by the hydraulic 

 jumps in these tests. 



Tests examining the performance of fall chinook 

 salmon in a fishway under a uniform plunging 

 or streaming flow indicated there was no significant 

 difference between the rate of ascent in the two 

 flow conditions. Respective rates of ascent under 

 plunging and streaming flows were 37 and 34 

 pools per hour. 



Table 4 — Chinook solmon and steelhead trout rate of movement 

 in light and dark channels. Water velocity — 4 feet/second, 

 distance measured — 30 feet 



.MWf^^ 



Figure 1 9. — Covered fishway used in darkened passage 

 experiments. All laboratory lights were turned off 

 during dark tests. 



The influence of hydrauhc conditions in the 

 pools on the pattern of ascent in the endless 

 fishways was previously noted. The change in 

 pool hydraulics brought about by restricting the 

 length of the weirs in the l-on-8-slope fishway was 

 sufficient to correct the pattern of movement to 

 that desired, i.e., encourage fish to utilize each 

 pool for resting (figs. 13 and 14). 



EFFECT OF LIGHT ON FISH MOVEMENT 



Measurement of the swimming performances of 

 chinook salmon and steelhead trout in light and 

 dark channels indicated that the movement of 

 both species was significantly slower in the dark 

 channel (table 4). In these tests the fish were 

 light adapted before they entered the channels. 

 Light intensities averaged approximately 750 foot- 

 candles in the "light" channel and 0.3 foot-candle 

 in the "dark" channel. 



In contrast to the foregoing channel experi- 

 ments, a series of passage trials in light and dark 

 fishways (fig. 19) indicated that faster movement 

 occurred under the dark condition (table 5). 

 These data apply principally to steelhead trout 

 (98 percent steelhead and 2 percent chinook 

 salmon). Before entering the fishway, fish were 

 light adapted under the "light" condition and 

 dark adapted under the "dark" condition. Pre- 

 vailing light intensities in the fishways were about 

 800 foot-candles in the Hght and less than .01 

 foot-candle in the dark. Further research will be 

 necessary to explain why the fish moved so securely 

 and effectively through the fishway pools in the 

 (lark, apparently oriented by the patterns of jets, 

 eddies, and turbulences, while in a straight, level 

 channel with a uniform laminar-type flow they 

 iip[)('iir('(l to move only with great caution in the 

 (lurk. 



12 



