the upstream half of the array. A further desirable effect of this 

 application is realized in that more sea lampreys are retained in a 

 paralyzed state in the electrical field until killed by suffocation. 



{$) The ground-mounted, non- buoyant electrodes were not 

 satisfactory at least in the stage of development achieved during 

 tests in l°£l. Although the initial cost of a ground-mounted electrode 

 array was calculated to be less than that for a system of suspended 

 electrodes, this advantage was outweighed by numerous disadvantages 

 both electrical and mechanical. Siltation around the electrode mount- 

 ings caused appreciable losses of power into the stream bed. Further 

 losses of power resulted from the close proximity of the electrodes 

 to a good electrical ground in the form of the steel anchor pins, Suscep- 

 tibility to damage or displacement by heavy floating debris was great. 

 Wire leads to electrodes, lying on the bed of the stream, were easily 

 damaged and difficult to repair. From the mechanical standpoint, the 

 spring-loaded hinge was not a satisfactory electrode mounting. No prac- 

 tical method could be found to prevent debris from collecting inside the 

 hinge and jamming it open. 



Ground-mounted, buoyant electrodes likewise were found to be 

 unsatisfactory. In addition to exhibiting most of the drawbacks indi- 

 cated above, the buoyant type produced distorted electrical fields and 

 drew unnecessary amounts of power during low-water stages when the elec- 

 trodes were lying almost flat on the water. 



(6) It was observed that spawning runs of certain food and 

 game species, migrating simultaneously with the lampreys, were wholly 

 or partially blocked by the AC field. These species did not "lead" 

 well along the margin of the electrical field and enter the upstream 

 traps (from which they could then be transferred upstream). Some of 

 the species which were thus blocked, such as the suckers, can spawn in 

 the lake properj consequently their exclusion from stream spawning 

 grounds is not a serious consideration. However, in the interests of 

 protecting the runs of several species which are not so adaptable in 

 their habits, experiments were performed with a DC guiding field located 

 on the downstream side of the electrical weir. No positive evidence of 

 the effectiveness of this accessory device was obtained. Its failure 

 to guide fish into the upstream trap may have been due to one or both 

 of the following reasons: (a) The shield screen, which was necessary 

 to isolate the trap electrically from the strong AC fields at the up- 

 stream end of the weir, so completely dispersed the DC guiding field at 

 the attracting electrode (anode) (as evidenced by voltage gradient 

 measurements in this area) that the fish were not able to sense the 

 positive direction; (b) DC voltage gradients were insufficient as a 

 result of power limitations of the device (100 volts DC at one ampere). 



