In the Fisheries-Engineering Laboratory at Bonneville 

 Dam, we made extensive studies on economical and efficient 

 means of passing fish over dams (fig. 24). The investi- 

 gations were financed by the U.S. Army Corps of Engineers. 



The laboratory stands on a short bypass to one of the 

 main fish ladders, from which migrating fish are diverted. 

 Their behavior and performance are measured as they pass 

 through e.xperimental structures. Recent studies revealed 

 how water temperature, types of flow, and light influenced 

 the behavior and performance of adult salmon and steel- 

 head trout within fish-passage facilities. 



Response to Temperature 



To test the response of migrating adult salmon and steel- 

 head trout to different water temperatures, the fish were 

 given a choice of entering either of two channels (fig. 25). 

 In one channel, the water was at river temperature (50°- 

 70° F.), to which the fish had been acclimated; in the other, 

 temperatures ranged from 15° F. warmer to 7° cooler than 

 the river temperature. 



Although more fish entered the channel with water at 

 river temperature, many fish voluntarily entered water up 

 to 7° F. above or below that of the river. A few fish entered 

 water as warm as 80° (15° F. wai-mer than river temper- 

 ature), but none entered water above 80° F. When given 

 a choice of entering water either 7° F. above or below river 

 temperature, more fish entered the cooler water. 



Attracting Fish 



Ideally, water flow and other conditions at fishway en- 

 ti-ances should attract the fish so they move past a dam with 

 minimum delay and maximum ease. In their search for 

 ways to speed the passage of fish, biologists tested various 

 hydraulic and light conditions to attract fish into fishway 

 entrances and into submerged orifices. 



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FIGURE 24.-TOP. The Fisheries-Engineering Research Lab- 

 oratory (arrow) at Bonneville Dam on the Columbia River. 

 BOTTOM. Drained test channel inside laboratory. 



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