the fishway. The rate of ascent in a l-on-8-slope 

 fishway of proper hydrauUc design is approxi- 

 mately the same as in a l-on-16-slope fislivvay. 

 The second is tliat for practical purposes the rate 

 of fish movement in fishways is independent of 

 the numbers of fish. Groups of fish in the labora- 

 tory tests moved as fast as individual fish. This 

 behavior pattern reduces the concern that the 

 rate of fish movement might drop suddenly if a 

 fishway became crowded. 



FISH SWIMMING ABILITIES 



Tests with adult chinook salmon and steelliead 

 trout have shown that all fish negotiated an 85- 

 foot flume when velocities were approximately 8 

 feet per second. When the velocity was increased 

 to 13 f.p.s. approximately 50 percent of the chinook 

 and 9 percent of the steelliead failed to pass the 

 flume. Thus, somewhere in the range of 8-13 

 f.p.s., we can expect some of the fish of these 

 species to be blocked when the distance to be 

 negotiated approaches 100 feet. 



Table 3. — Response of chinook and silver salmon and steelhead 

 trout presented with a choice between entering a high- or a 

 low-velocity channel 



Figure 16. — Experimental channel with a wafer veloc- 

 ity oM 6 feef per second appears on right. Entrance 

 to channel on left is screened to prevent access 

 during swimming ability tests. 



I Includes all size groups. 



Additional tests were conducted in which sal- 

 monids were subjected to a velocity of approxi- 

 mately 16 f.p.s. (fig. 16). Marked declines in 

 performance were noted. About 95 percent of 

 the chinook salmon and approximately 50 percent 

 of the steelhead failed to negotiate the 85-foot 

 flume. 



Differences in performance with respect to size 

 were also noted. Two size groups were considered 

 (1) fish estimated at 24 inches and under, and (2) 

 fish over 24 inches. Respective performance 

 (distance negotiated) of the two groups in velo- 

 cities of approximately 13 and 16 f.p.s. are shown 

 in figure 17. Clearly, "large" fish were capable of 

 greater performance than "small" fish. 



Measurements of the rate at which salmonids 

 travel in a channel under a variety of water 

 velocities suggest that a velocity of 2 f.p.s. may 

 be most satisfactory for transportation purposes. 

 These experiments utilized fall chinook salmon, 

 silver salmon, and steelhead trout which were 

 subjected to water velocities ranging from 2 to 

 16 f.p.s. Rate of movement in relation to the 

 channel is shown in figure 18. Chinook salmon 

 made their fastest progress at 2 f.p.s. and exhibited 

 a progressive decline in rate of movement up to 

 13 f.p.s. Conversely, steelhead trout and silver 

 salmon indicated an increase in performance as 

 the water velocity increased up to 8 f.p.s. The 

 three species tested registered approximately 

 equal median rates of movement (5-f- f.p.s.) in a 

 water velocity of 8 f.p.s. Any slight advantages 

 the higher flows may have in expediting the move- 

 ment of certain species are minimized by the fact 

 that considerably more water would be required 



10 



