Responses to diffei'ent light intensities (fig. 26) and 

 turbulence were also tested in the 5i/->-and 2-foot channels. 

 Although the responses varied by species and with velocity 

 of flow, the fish tended to avoid entering a channel with a 

 dark entrance and were reluctant to pass through turbulence 

 created by a screen of compressed air. 



FIGURE 25.— Obscners follow fish through the temperature 

 test channels at Bonneville Dam. Heated or cooled water can 

 be supplied to either channel by regulating valves from heaters 

 and chillers without changing hydraulic conditions in either 

 channel. 



Into fishway entrances. — Because previous observations 

 indicated that adult salmon may be attracted to stronger 

 flows, tests were performed to determine if a high-velocity 

 water jet might attract fish to fishway entrances. Adult 

 salmon and steelhead trout were given a choice of entering 

 either wide or narrow channels. It appears that fish may be 

 attracted to high-velocity flows, but they might not enter a 

 passageway if the entrance is too narrow. 



FIGURE 26.-TOP. Testing the response of fish to illuminated 

 and dark channels at Bonneville Dam. BOTTOM. Fish were 

 reluctant to pass through a screen of air bubbles. 



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