Voltage gradients created in the water during each test 

 conducted were measured, recorded, and correlated with effects on 

 fish and lampreys. A specially designed probe and a vacuum tube 

 voltmeter were used to obtain these measurements. A more detailed 

 description of test instruments is included in a later section. 



Summary of results in 195>1 



(1) The experimental electromechanical weir and trap, 

 utilizing as little as 2 KW of power, effectively killed, trapped, 

 or diverted all sea lampreys entering the river. The results ob- 

 tained at this low power level are amazing in view of the fact that 

 it was necessary in this river to energize 1,U00 cubic feet of water 

 and that an appreciable percentage of the power input was dissipated 

 in the stream bed. By way of comparison, it might be pointed out 

 that this power consumption is roughly four times that required by a 

 domestic electric iron. 



(2) Specifically, satisfactory results were achieved util- 

 izing the 2 : 1 voltage ratio between the upstream and downstream 

 rows of electrodes with voltage levels as low as 70/35 (2 KW power 

 consumption). Similar results were obtained with the 1 : 1 voltage 

 ratio between rows with voltage levels as low as 70/70 (2.7 KW power 

 consumption). At lower voltage levels in both applications (60/30 and 

 60/60 and lower combinations) some escapement of lampreys occurred. 

 Consideration of all factors indicated, however, that in general prac- 

 tice somewhat higher voltage levels than the minima found effective 

 should be used in order to provide some margin of safety. Input volt- 

 ages in the order of 110 provided an adequate margin of safety and at 

 the same time had the distinct advantage of being easily obtained from 

 conventional power sources (power line or generators). 



(3) It was determined that a minimum voltage gradient of 

 0.75 volt per inch must exist in the water between electrodes at least 

 in the upstream half of the array (center row to upstream row of elec- 

 trodes) if the electrical field is to block the lampreys effectively. 

 Where weaker gradients exist between electrodes in the upstream half 



of the array, some escapement of lampreys through the field occurs. If 

 an adequate margin of safety is desired, the minimal voltage gradient 

 between electrodes of the common and upstream rows must be at least 1.0 

 volt per inch. 



(U) It was tentatively considered desirable to maintain the 

 effect of a so-called "incremental field" created by the application 

 of voltage levels in a 2 : 1 ratio between the upstream and downstream 

 rows of electrodes. The weaker electrical field on the downstream side 

 of the array seemed to repel migrant food and game fishes before they 

 could be harmed by abrupt contact with the higher voltages required in 



8 



