FioTJBE 11. — Electrode array trap with throat closed (arrow) and sectioned brail raised. 



panels manipulated to create the desired water 

 velocity for the next test. This procedure was fol- 

 lowed for the duration of the experiment. Each 

 complete test took 96 hours : stoplog adjustment, 8 

 hours; control period, 40 hours; maintenance, 8 

 hours ; and power-on, 40 hours. 



COMPOSITION OF CATCH 



Most of the test fish were wild, downstream 

 migrants of the Yakima Eiver system. One- 

 hundred twenty-nine thousand juvenile salmon 

 and trout were captured. About 50 percent were 

 Chinook salmon, 32 percent coho salmon, and 18 

 percent rainbow-steelhead trout. The chinook 

 salmon belonged to age-groups and I and had 

 average fork lengths of 89 and 133 mm., respec- 

 tively. The coho salmon were age-group I fish and 

 averaged 131 mm. The rainbow-steelhead trout 

 were age-group I and older and had a mean length 

 of 198 mm. 



EFFECT OF TEST VARIABLES ON 



EFFICIENCY OF FISH-GUIDING AND 



COLLECTING 



Preliminary analysis indicated that the elec- 

 trode array and array trap collected a relatively 

 high percentage of fish, even during the power-off 

 (control) conditions. To distinguish between the 

 fish-collecting efficiency of the total guiding sys- 

 tem (electrode array and array trap) with the 

 power on and the actual fish-guiding efficiency of 

 the electrode array and electrical field alone, the 

 experimental results are presented in three sec- 

 tions: (1) electrode array energized plus array 

 trap — percentage of fish collected by the electrode 

 array and array trap with the electrode array 

 energized, (2) electrode array nonenergized plus 

 array trap — percentage of fish collected by the 

 electrode array and array trap under control con- 

 ditions, and (3) electrode array energized without 



FISH-GUIDING EFFICIENCY OF AN ELECTRICAL GUIDING SYSTEM 



317 



