Table 1. — Catch results with 24 drags each of a 12.5-m 

 (headrope) standard trawl — no electrodes, versus a 

 12.5-m (headrope) electrical trawl — power off with 

 electrode array 1. RV Kaho cruise No. 48, Lake 

 Michigan, May 14 - June 14, 1968. 



1 Other species listed according to descending abun- 

 dance were as follows by weight: spottail shiner, trout- 

 perch, sculpin, lake herring, darter, logperch, stickleback, 

 common whitefish. Other species listed according to de- 

 scending abundance were as follows by number: spot- 

 tail shiner, sculpins, trout-perch, darter, logperch, lake 

 herring, stickleback, common whitefish. 



mouth of a moving net (Shentaykov, 1960, 1965) . 

 The results of the second experiment compar- 

 ing the effects of electrical lines of flux for three 

 electrode arrays on catch rates are shown in 

 Table 2. The following results were obtained 

 with the three different electrode arrays: 



Array 1 — The average catch per drag for 

 power on and power off is shown in Table 2. 

 Catches with power on averaged 56.0 kg of 

 fish per drag, and those for power off drags 

 averaged 48.9 kg of fish. The catch rate with 

 power on was 1.34 times or 34.6% greater 

 than that with power off. 



Array 2 — This array system with power on 

 was the most successful method tested and an 

 average of 4.3 kg of fish per drag were cap- 

 tured versus a catch of 2.3 kg of fish per drag 

 with power off. In this case the catch rate 

 with power on was 1.86 times or 86.9% more 

 than the catch rate with power off. 



Array 3. — This system with power on was 

 the least effective of the three arrays tested. 

 The average catch rate with power on was 

 25.8 kg of fish per drag versus 21.1 kg of fish 



per drag with power off._ The power on catch 



rate was 1.22 times or 22.3% more than the 



power off catch rate. 



Under the hypothesis that the electrical trawls 

 with power on and power off have an equal 

 chance of catching fish, about half of the total 

 number of fish caught would be expected to occur 

 during power on and half to occur during power 

 off. This would also hold true for the standard 

 trawl with and without electrodes. 



The data in Table 3 show that the overall 

 catch rate of the standard trawl was significant 

 (P < 0.01, 1 degree of freedom) . The lake trout 

 catch rate with the standard trawl was not sig- 

 nificant (P > 0.01, 1 degree of freedom). In 

 general, we can assume the fish avoid capture 

 when vertical electrode arrays spaced 0.3 m apart 

 are placed across a trawl's mouth area. 



Overall, the catch rate with arrays 1, 2, and 3 

 with power on was significant (P < 0.01, 1 de- 

 gree of freedom); however, there was not a 

 significant difference in the catch rate with in- 

 dividual species to each array tested. The catch 

 rates of alewife with array 2 and lake trout with 

 arrays 1, 2, and 3 were not significant (P > 0.01, 

 1 degree of freedom) with power on (Table 4). 

 The difference in catch rates with power on 

 lies in the reaction of species to the equipo- 

 tential lines of flux created by the different ar- 

 rays. By electrically disconnecting every other 

 cathode, array 2, the equipotential lines of flux 

 within the array system were changed. With 

 this array system the lines of flux would be more 

 dense in the immediate vicinity of each cathode 

 element than with arrays 1 and 3. Since the 

 electrical field is more "open" with array 2, the 

 visual avoidance to electrode arrays per se ex- 

 perienced in the first experiment is offset by its 

 increased catch rate. 



Although statistically there is a significant 

 difference between power on and power off catch 

 rates, it does not follow that it has to be com- 

 mercially significant since the commercial fish- 

 erman is interested in pounds of fish caught and 

 not numbers of fish caught. 



Straight line projection of the data with ar- 

 ray 2 shows the potential of electrical trawling 

 gear during a commercial fishing year in the 

 Great Lakes of 150 days or 1200 hours with a 

 commercially significant catch rate of $7.50 (ex- 

 vessel value) per one-half hour of effort. These 

 projections show that a commercial vessel would 



