The methods followed in experiments conducted in the field 

 were generally comparable to those used in the laboratory tests, al- 

 though procedures were varied slightly according to conditions encoun- 

 tered at the field sites. Further details are given in the discussion 

 of the results. 



Reactions of different species to pulsated 

 direct current 



The results of 798 tests on more than 1,000 fish proved that 

 some species when subjected to an applied voltage gradient of pulsated 

 direct current under given conditions can be made to move toward, or be 

 assembled at, the anode or positive electrode. It was determined in 

 the tests that fish of a particular size led best at a definite voltage 

 level. If the voltage gradient lies within the effective range for the 

 size of the fish, the movement to the anode will be immediate and deter- 

 mined. The results described in this study are based on the reactions 

 cf white suckers, brook trout, and rainbow trout. 



Laboratory tests on white suckers. — Nearly 2^0 tests were con- 

 ducted in the laboratory with wliite suckers which ranged in length from 

 9 to 16 inches. They were subjected to a series of tests encompassing 

 the entire range of variables which the equipment was capable of produc- 

 ing. The water temperature throughout the laboratory experimentation 

 varied from 36° to 39° F. 



The tests failed to elicit from the suckers a definite movement 

 toward the anode or even any indication of orientation to the flow of 

 electrical current. Some of the tests appeared to indicate a trend of 

 movement to the anode end of the tank; however, rechecks and additional 

 tests invariably failed to yield confirming results. The voltage gradient 

 reojaired to produce electronarcosis varied inversely as the duty cycle. 



Field tests on white suckers . — The results of the field tests 

 on leading white suckers were exactly opposite those obtained in the 

 laboral,crj', in that verj'' positive involuntary and persistent movement 

 toward the anode was observed. The device was installed in Carp Creek 

 which was approximately 2$ feet wide and averaged 18 inches deep at the 

 experimental site. During the testing period, water velocity was almost 

 negligible and water temperature ranged from 75° to 78° F. The electrode 

 array was as described in the section on equipment. 



Only 11 suckers were available for experimentation; these fish 

 had been captured in a mechanical weir and trap located just below the 

 leading device. The fish were subjected to essentially square waves of 



