100 BULLETIN OF THE BTJKEAU OF FISHERIES 



rather than a preserver of fish. In the light of these facts, J. E. Yates, assistant 

 engineer of the Pacific Power & Light Co., determined to have an investigation made 

 to find, as far as practical, the facts about the electric fish screen. The results of 

 this investigation are given in this report. 



ACKNOWLEDGMENTS 



Thanks are due especially to J. E. Yates for advice, assistance, and suggestions 

 given dui-ing the investigation. Both the Oregon Fish Commission and the Oregon 

 Game Commission have shown great interest in the experiments. The Oregon 

 Fish Commission very generously lent facilities at the Bonneville fish hatchery and 

 provided the fish used in the experiments. Eugene Howell, superintendent of the 

 Bonneville hatchery, and his assistants gave invaluable help with the experimental 

 work. Dean John N. Cobb, of the University of Washington, furnished drawings 

 of one of the electric "stops" used in irrigation canals in Washington. H. B. Holmes, 

 biologist with the United States Bureau of Fisheries, gave much valuable counsel and 

 had great interest in the entire investigation. The Pacific Power & Light Co. financed 

 the work. 



PROBLEMS INVESTIGATED 



The following problems were studied during the course of the experimental work 

 at Bonneville, Oreg.: 



1. What uniform voltage gradient in water will cause a fish to become paralyzed, 

 and how does this voltage gradient vary with the length of the fish? 



2. How does the voltage gradient and duration of application affect the mor- 

 tahty of fish subjected to excessive voltage gradients? 



3. Do fish subjected to electric shocks in various degrees suffer any after effects 

 other than those immediately observable? 



4. What influence does the resistivity of the water in which the fish are immersed 

 have upon the voltage gradient required to produce paralysis? 



5. What variation in water resistivity is found in various rivers and streams? 



6. Do fish, when swimming into an electrified area, such as that around an 

 electric screen, sense the direction of the danger? 



7. Does the relation of the lines of electric-current flow and the equipotential 

 surfaces with respect to the opening protected and the direction of water flow in the 

 stream have any influence on the effectiveness of an electric screen? 



8. Will an electric screen effectively prevent flsh entering a protected area? 



EXPERIMENTAL DATA 

 VOLTAGE GRADIENT REQUIRED TO PRODUCE PARALYSIS 



One of the most fundamental things needed to be known in connection with 

 the application of electricity to fish screens was the order of magnitude of the voltage 

 gradient required to produce paralysis and cause fish to lose all control of movement. 

 To obtain these data, an aquarium with glass sides and wood bottom and ends was 

 fitted with two parallel metal plates having as nearly as practical the same area as 

 the QVQSS section of the aquarium, These plates were connected with the secondary 



