ELECTRODES 



WATERFLOW 



Figure 7. — Wiring pattern of electrode array. 



downstream from the electi'ode array trap. All fish 

 escaping past the electrode array were stopped by 

 revolving drum screens (fig. 12), which diverted 

 them to an underground bypass leading to an 

 inclined-screen tvup. Four wooden troughs adja- 

 cent to the inclined-screen trap held the captured 

 fish while they were being counted and identified. 

 These troughs were 20.3 cm. deep, 22.9 cm. wide, 

 and 167.6 cm. long (fig. 13). Each was divided 

 into three sections by removable screen partitions 

 and fitted with an overflow standpipe at one end. 

 A constant flow was fed to the troughs from a 

 headbox upstream from the inclined-screen trap. 

 The troughs were placed so tlie end with the stand- 

 pipe was above an open flume which carried water 

 from the inclined-screen trap to the Yakima Kiver. 



EXPERIMENTAL DESIGN 



The variables tested were three water velocities 

 (0.2, 0.5, and 0.8 m.p.s.), four test periods (varia- 

 tions among the test periods were due to uncontrol- 

 lable environmental changes such as temperature, 

 turbidity, and water resistivity), and three species 

 of fish — Chinook salmon, Oncoi'hynchus tshawyt- 

 scha; coho salmon, 0. kisutch; and rainbow-steel- 



liead trout, Salmo gairdneri.- Table 2 shows the 

 sequence of tests. The eft'ect of each water velocity 

 on the fish-giiiding efficiency of the electrode array 

 was tested once during each period. The experi- 

 ment ran 50 days (April 21 to June 9, 1962) ; 

 testing was continuous except for a 1-day inter- 

 ruption due to power failure during an electrical 

 storm. 



The effect of each of the three water velocities 

 on the fish-gniding efficiency of the electrical sys- 

 tem was determined by comparing the number of 

 individuals of each of the three species of fish 

 captured in the electrode array trap during a spe- 

 cific test jjeriod with the total number of the same 

 species taken by the array trap plus the inclined- 

 screen trap durmg that period. 



Water conditions in the experimental canal were 

 checked periodically. Velocity was measured every 

 2 hours with a Gurley current meter (No. 622-E)^ 

 at the downstream end near the middle of the 



" The term rainbow-steelhead trout, as used In this paper, 

 Includes both seaward migrants and residual members of the 

 species. 



•Trade names referred to In this paper do not imply endorse- 

 ment of commercial products by the Bureau of Commercial 

 Fisheries. 



314 



U.S. FISH AND WILDLIFE SERVICE 



