were closed at the end zones to hold the 

 fish at the conclusion of the test. Then 

 we dip-netted the fish from the experimental 

 area, separated them for size, and placed 

 them in the holding areas until the tests 

 for that day were completed. Remarks on the 

 behavior of the fish were recorded for each 

 test. 



Two men were required for each test. 

 When the men at the switching unit had 

 turned on the power to energize the elec- 

 trode array and had received a signal from 

 the second man, he quickly raised the fish 

 release enclosure to liberate the fish. 



Following the tests for each day, the 

 two size groups of once-shocked fish were 

 returned to separate holding pens in lake 

 water. These fish were not exposed for the 

 second time until after at least 48 hours. 

 Twice-shocked fish were measured for total 

 length and destroyed to make holding space 

 available for new lots of fish. 



RESULTS AND DISCUSSION 



We recorded the behavior of groups of 

 squawfish in each test in order to determine 

 the effects of the different levels of 

 potential, pulse frequency, and pulse dura- 

 tion; also counts were made of the number of 

 fish that were effectively led under the 

 different electrical conditions. 



Description of Behavior 



The squawfish reacted instantaneously 

 to the potential and pulse frequency levels 

 used in these experiments. The pattern of 

 the reactions of the squawfish in the ener- 

 gized fields depended more upon changes in 

 pulse frequency than potential. In fields 

 of pulse frequency of 2 pulses per second, 

 at the three levels of potential: (1) the 

 squawfish appeared to feel the electrical 

 fields, showed no loss of equilibrium, and 

 responded favorably to the direction of the 

 electrical fields; (2) the swimming speed of 

 the individual fish varied from slow to 

 swift; (3) some fish circled in the middle 

 of the array before orienting themselves to 

 the direction of the electrical fields; (4) 

 some fish swam rapidly against the direction 

 of the electrical fields and into the "nega- 

 tive" end zone; and (5) some fish swam 

 rapidly against the direction of the elec- 

 trical fields, but their swimming speed was 

 slowed to such an extend that (a) they 



barely reached the end zone, or (b) they 

 suffered electroparalysis and thus never 

 left the electrode array. Mamy of those 

 fish swimming against the direction of the 

 electrical fields appeared to jerk their 

 heads in response to the pulse, which, 

 however, was not strong enough to reverse 

 their direction. 



In fields of pulse frequency of 5 

 pulses per second, at energy levels of 

 potential of 60 and 75 volts: (1) the 

 Squawfish appeared to feel the electrical 

 fields noticeably, revealing loss of equi- 

 librium in from 1 to 8 fish in one-third 

 to one-half of the tests; (2) swimming was 

 sluggish or difficult, the speed slow to 

 moderate; (3) the squawfish generally 

 showed no leading response to the direction 

 of the electrical fields; and (4) most of 

 the fish in half of the tests at the level 

 of potential of 75 volts remained in the 

 middle of the electrode array. At the 

 level of potential of 90 volts: (1) 1 to 

 10 squawfish, in almost every test, suf- 

 fered electroparalysis; (2) swimming was 

 sluggish or difficult; (3) the squawfish 

 showed no leading response to the direction 

 of the electrical fields; and (4) most or 

 all of the fish in each test remained in 

 the middle of the electrode array. 



In fields of pulse frequency of 8 

 pulses per second, at levels of potential 

 of 60 and 75 volts: (1) squawfish felt 

 the electrical fields very noticeably, 

 revealing loss of equilibrium in from 2 

 to all 10 fish in all tests; (2) swimming 

 was sluggish or difficult, with loss of 

 motion in some fish; and (3) most of the 

 fish remained in the middle of the elec- 

 trode array. At the level of potential of 

 90 volts: (1) 3 to 10 squawfish in each 

 test suffered immediate or nearly immediate 

 electroparalysis; and (2) when electro- 

 paralysis was not immediate, the movements 

 of the fish were generally quite violent, 

 and, in mcuny cases, excellent leading 

 response of short duration was achieved. 

 Typically, an individual squawfish made a 

 violent lunge at the moment of release 

 within the sequentially pulsed electrical 

 fields. This action carried the fish 2 to 

 3 feet from the release area, or approxi- 

 mately half the distance to the "positive" 

 end zone. This lunge endured usucdly for 

 the time interval of one sweep of the pulse 

 through the four electrical fields. As the 

 time interval of the pulse to sweep the 

 four fields once is one-half second at 8 



