that the device caused some mortality among migrant fishes when the 

 horizontal electrode was located downstream from the vertical elements. 

 The character of the electrical field established between the vertical 

 suspended electrodes and the horizontal submerged electrode is such 

 that where the installation is situated in deep, sluggish water, mi= 

 grant fish swimming near the surface can cross above the horizontal 

 electrode., Approaching closer to the vertical electrodes they become 

 stunned and are killed when they fall to the bottom inside the hori- 

 zontal electrode in the strongest area of the electrical field. This 

 mortality did not occur at Carp Creek where shallow water and swifter 

 stream velocities existed. 



Evidence as to the amount of fish mortality resulting when 

 the horizontal, submerged electrode was placed upstream from the verti- 

 cal elements was not obtained during the single test conducted at 

 Hibbards" Creek. Fish migration in the stream had ceased when this 

 test was in progress „ However , the behavior of the lampreys during 

 this test suggested that fish mortality might be minimal with this elec- 

 trode arrangement, 



A test conducted in Carp Creek with an array consisting of 

 only two horizontal, submerged electrodes placed parallel on the stream 

 bed indicated that under restricted conditions a barrier to lamprey and 

 fish movement could be effected with this simple equipment, With elec- 

 trodes placed 10 feet apart at a point where the water averaged 12 

 inches deep, 110 VAC was applied across the elements! sea lampreys were 

 unable to penetrate this electrical barrier, Only 1*80 watts were re- 

 quired to energize the device. 



Further experimentation with this device is necessary in order 

 to establish its working limits. With this electrode arrangement, the 

 area of lowest electrical field strength and most likely point- of escape- 

 ment of lampreys through the barrier is at the surface of the water dir- 

 ectly above a point midway between the electrodes. At any fixed input 

 voltage,, the strength of the electrical field at this weakest point is 

 a function of the distance between electrodes and the water depth. Ulti- 

 mate use of the device will be restricted by the maximum stream depth at 

 which satisfactory voltage gradients can be established at this weakest 

 point when a given optimum spacing between electrodes for an input of 

 110 VAC is used. 



(k) Electrode size, conformity «, and efficiency 



It has been concluded that the most suitable electrode materials 

 for use in sea lamprey electrical weirs are the following in the order 

 presented? (a) l/?-inch diameter thin wall conduit, rough surface, 

 (b) 1/2-inch diameter thin wall conduit, smooth surface, (c) l/2-inch 



37 



