ELECTRIC FISH SCREEN 



By F. O. McMillan 

 Associate Professor of Electrical Engineering, Oregon State College 



CONTENTS 



Page 



Fish-protection problem 97 



Protective laws 98 



Mechanical screens 99 



Electric screen 99 



Acknowledgments 100 



Problems investigated 100 



Experimental data 100 



Voltage gradient required to produce paralysis 100 



High-frequency test 103 



Continuous-current test 103 



Duration of application and mortality 103 



Observations during paralysis and recovery 104 



Observations after electrical tests • 106 



Influence of water resistivity on the paralysis-voltage gradient 107 



Water resistivity of various streams 108 



Do fish sense the source of an electric field and avoid it? 111 



Direction of the electric field with respect to the protected opening and the stream flow. . 113 



Electric screens should be used as deflectors, not stops 115 



Last fish-screen test at Bonneville 115 



Design of electric fish screens 122 



Conclusions 124 



Bibliography 128 



FISH-PROTECTION PROBLEM 



Every year millions of game fish and fry of anadromous food fish are carried out 

 on the fields and left to die because they have followed some irrigation canal instead 

 of the main stream channel. Many others are killed by mechanical injury or sudden 

 pressure change incident to passing through hydrauhc turbines. The problem of 

 protecting fish from these dangers is not new but probably is as old as the knowledge 

 of irrigation. However, as irrigation and power projects increase in size and number 

 and the supply of fish is depleted, the problem commands greater attention. As 

 early as 1895, Dr. C. H. Gilbert, of Stanford University, called the attention of 

 HoUister D. McGuire (then fish and game protector of Oregon) to the destruction of 

 blueback-salmon fry on the irrigation projects near Wallowa Lake (McGuire, 1896). 

 This led to legislation in Oregon requiring the screening of waterways dangerous to 



97 



