(3) Ele ctrode array pattern, circuitry, and power requirements 



Experimentation with the several devices indicated that a var- 

 iety of electrode array patterns were effective at low power demands 

 provided the voltage gradients produced in the water were not below the 

 minimum of 0.75 volt per inch discussed previously. 



Multiple-row, suspended electrode systems used with the elec- 

 tromechanical weirs and traps were readily adaptable for creating 

 either incremental or uniform electrical fields. Two methods of pro- 

 ducing incremental fields were tested at the Kewaunee River device of 

 which the first proved to be more economical in power requirements than 

 the second. 



In the first method, where incremental fields were produced 

 by maintaining equal spacing among all electrodes of all rows and apply- 

 ing one-half the AC line voltage (110) across the "B" and "C" rows, the 

 following results were obtained (interval between rows of electrodes in 

 the array held constant at I4 feet in all tests): 



(a) With a spacing of U feet between electrodes in each row, 

 minimum voltage gradients between electrodes of the "A" and "B" rows in 

 excess of 0.75 volt per inch were present in the water and sea lampreys 

 were unable to penetrate the upstream half of the array. Furthermore, 

 many lampreys which penetrated the lower half of the array where voltage 

 gradients were reduced were completely immobilized and, where they settled 

 to the bottom within the array, were killed by suffocation. Average water 

 depth at the weir site during this test was 12.5 inches; 1,533 watts were 

 required to energize the device. 



(A similar test conducted at the Squaw Creek installation with 

 smaller diameter electrodes set on 3-foot centers in rows spaced 3 feet 

 apart produced identical results. This array, considerably smaller than 

 that in the Kewaunee River, drew only 191 watts when the average water 

 depth at the weir site was 10.7 inches). 



(b) With a spacing of 6 feet between the electrodes of each 

 row, minimum voltage gradients between elements of the "A" and "B" rows 

 averaged 0.70 volt per inch. Sea lampreys were still unable to traverse 

 the upstream half of the array. Occasional individuals, however, were 

 observed to penetrate this latter area quite deeply although none escaped 

 through the field. Had water velocities within the array been less than 

 the minimum 1.35 f.p.s. existing during all these tests, it is extremely 

 doubtful whether a complete blockade of the sea lamprey run would have 

 been accomplished with this electrode spacing. A subsequent test indi- 

 cated that even at these water velocities, any greater spacing of elec- 

 trodes within a row permitted lampreys to escape through the electrical 



32 



