490 
pointj the second and third groups of experi- 
ments were conducted, the results of which 
are given in the following sections. 
Interrupted Direct Current 
3:1 On-Off Ratio 
The results of tests using a 3:1 on-off ratio 
are shown in Table 3. From this table it can 
be seen that the desired effect of holding the 
fish at the positive pole for the full time of 
each test was not achieved on all fish until 
an average current value of 8 amperes was 
reached, and then only in the tests having 
25 interruptions per second. However, an 
analysis of the results shows that a significant 
deviation from the expected average of 30 
seconds was reached in the tests using 7 am- 
peres; for example, at five interruptions per 
second t = 3.18, P == 0.01. The higher am- 
perage required when using the 3:1 on-off 
ratio resulted in a loss rather than a gain in 
the efficient use of power. It was then decided 
to decrease the duration of the on- (pulse) 
period, using a 1:3 on-off ratio. 
Interrupted Direct Current 
1:3 On-Off Ratio 
Recorded results of these tests are shown 
in Table 4. A significant variation from the 
expected average of 30 seconds was reached 
at an amperage of 2. At a current value of 3 
amperes and a frequency of 25 interruptions 
per second, all fish tested were immobilized 
at the positive pole. At a current value of 4 
amperes all fish tested at all frequencies 
showed the maximum effect possible. 
The quantitative data in the preceding ta- 
bles do not, of themselves, indicate the full 
effect which results when interrupted current 
and decreased on-period is used. Observation 
of the reaction of the fish left no doubt that 
the experiment using the shortest pulse pe- 
riod produced the most violent effects. With 
uninterrupted current the fish’s movements 
were slowed and inhibited. With interrupted 
current, as the individual shocks became 
shorter, the effect it produced became greater. 
PACIFIC SCIENCE, VoL VII, October, 1953 
At the shortest pulse period, with an effective 
current, the fish would often leap out of the 
water and would frequently skip along the 
surface, always moving directly toward the 
positive pole. 
Variation of Response 
with Frequency of Interruption 
A statistical analysis was made of the rela- 
tionship between frequency of interruption 
and time spent at the positive pole. From each 
group using interrupted current the recorded 
times at frequencies of 5, 15, and 25 were 
chosen. These were taken only from the two 
amperages just below the value that caused 
maximum effect (60 seconds at the positive 
pole). The only exception to this was the 8 
ampere 3:1 on-off series; these data were add- 
ed because the maximum effect was shown 
only in the 25 interruptions per second tests 
(Table 3). The following were included in the 
analysis: 1:1 ratio, 3 and 4 amperes; 3:1 ratio, 
6, 7, and 8 amperes; 1:3 ratio, 2 and 3 amperes. 
The effect of different on-off ratios, as well 
as the effect of the various amperages, was 
separated by analysis of variance methods 
from the effect due to frequencies of inter- 
ruption. The data were transformed logarith- 
mically to conform more closely to normal 
distribution. The analysis provided the in- 
formation given in Table 5. 
There are significant differences among fre- 
quencies (F = 6.73; P = 0.01). Inspection of 
the data shows that the higher time averages 
are associated with the higher frequencies. 
TABLE 4 
Mean Time (in Seconds for 5 Fish, 2 Trials Each) 
Spent in the Positive Section of the Tank at 
Various Frequencies and Amperages of Inter- 
rupted Current with 1:3 On-Off Ratio 
AMPERES 
frequencies 
5 
15 
25 
2 
41.3 
■ 44.5 
55.9 
3 
56.3 
52.0 
60.0 
4 
60.0 
60.0 
60.0 
