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

 minimum voltage gradients between electrodes of the two rows averaged 

 0.98 volt per inch. Sea lampreys were unable to penetrate the array. 

 Average water depth at the weir site during this test was 10.5 inches; 

 only 1,192 watts were required to energize the array. 



This was the simplest and most economical multiple-row, 

 suspended electrode system developed during the present tests which 

 effectively blocked a sea lamprey run. Although extremely effective 

 in a relatively shallow location in the stream where water velocities 

 were swift, the general utility of this simple array has not been deter- 

 mined. It remains to be demonstrated whether it will function with 

 equal effectiveness in deeper and more sluggish water. 



A nominal disadvantage in the utilization of uniform electri- 

 cal fields with these arrays is that few lampreys are killed by the 

 device. Meeting first an electrical field of paralyzing intensity rather 

 than the zone of reduced intensity characteristic of the incremental 

 electrical field, the lampreys cannot penetrate the area within the elec- 

 trode array. Stunned at or below the lower-most row of electrodes, they 

 are carried out of the electrical field by the water current and recover 

 rapidly. 



In all tests of incremental and uniform electrical fields, runs 

 of other fishes, particularly suckers, "led" well along the "fringe" 

 field (below the lowermost row of electrodes) and entered the weir-trap 

 with little or no observed mortality or blocking effect. This represents 

 a marked improvement over the similar device installed in the Ocqueoc 

 River in 1951. The improved efficiency of the Kewaunee River and Squaw 

 Creek installations in capturing migrant fishes for transfer upstream is 

 attributed primarily to careful location of the electrical blocking field 

 and weir-trap in each stream. Weir-traps were placed directly in the path 

 followed by the majority of migrant fish swimming upstream. In the Kewau- 

 nee River at the site chosen for the installation this path happened to 

 lie very close to one bank; at the Squaw Creek site most fish movement 

 occurred in midstream. Electrode arrays were then installed so as to pro- 

 vide "leads" to these points for those fishes traveling elsewhere across 

 the width of the stream. The tendency of the earlier Ocqueoc River de- 

 vice to block rather than "lead" and capture migrant fishes was undoubt- 

 edly due to improper location of the weir-traps which were adjacent to 

 the stream banks rather than in midstream where the majority of fish 

 movement occurred at that particular site. 



Another factor that contributed to the greater success of these 

 devices in "leading" and trapping fish was the rapid water velocities 

 occurring at the loci of installation (Kewaunee River* range - 1.35 to 

 1.5U f.p.s., average - l.Ul f.p.s.; Squaw Creek: spot reading - 1.13 

 f.p.s.). The swifter waters in the riffle areas over which the arrays were 

 installed discouraged or prevented fish from penetrating the "fringe" field 

 into areas of greater electrical current density where the alternating 

 current fields would tend to disorient them. 



3U 



