491 
I Response of Fish to Direct Current — MORGAN 
I 
TABLE 5 
Results of Statistical Analysis of Relationship between Frequency of Interruption 
AND Time at Positive Pole 
SOURCE 
DEGREES OF FREEDOM 
SUMS OF SQUARES 
MEAN SQUARES 
Total 
20 
0.243032 
Blocks 
6 
0.175656 
0.029276 
Frequencies 
2 
0.035628 
0.017814** 
Discrepance 
12 
0.031748 
0.002645 
Observation of the effect at the various 
interruptions leads to the conclusion that the 
lower frequencies are not as effective as those 
in the middle range. If the pulse duration is 
short, this is particularly true. At low fre- 
quencies there is sufficient time after the fish 
receives the shock to enable it to turn par- 
tially or make other movements to escape the 
current. As a result, the fish pursues an erratic 
rather than straight course toward the posi- 
tive pole. In certain respects, the frequencies 
near the value of 15 per second have some 
advantages over higher frequencies used. At 
higher frequencies the fish receives such a 
rapid series of shocks that there seems to be 
insufficient time for it to react between shocks, 
thus greatly restricting its movements and 
slowing its progress toward the positive pole. 
At these higher frequencies, with an effective 
current, the fish often becomes immobilized 
at some distance from the pole. 
Relationship between Average 
and Peak Currents 
One very important fact that enters into 
the interpretation of the results of the experi- 
ments is that all interrupted-current values 
are average values. These values were adjusted 
to the desired reading on the ammeter while 
the interrupting mechanism was in operation. 
The peak amperage was not indicated by the 
ammeter during the tests because of the in- 
dicator’s inertia. The peak amperage is the 
maximum value that will be reached during 
the current-on period. For example, when the 
on-period equaled the off-period and the aver- 
age current value, as read on the ammeter, 
was 5 amperes, the peak current reached dur- 
ing each pulse was 10 amperes. This value 
was read on the ammeter when the interrupter 
was not in operation. 
From Figure 5 it can be seen that the peak 
current in all cases is similar. It is quite possi- 
ble that, were the exact current values neces- 
sary to achieve the desired effect known, the 
peak current in all cases might be equal. As 
it is, the effective average current value in 
Pea k 
Unit- •time period 
Unit" time period 1 
Fig. 5. Average and peak current considerations. 
Total power comparisons. 
