7116 ‎(2)‎

• UCREFRP Catalog Number: 7116
• Author: Baxter, G. and J. Simon
• Title: Editor
• USFW Year: Series
• USFW - Doc Type: 1970
• Copyright Material: YES

12

latter case the remaining pulse might be eliminated
by the use of 3-phase current (op. cit.).
Direct and alternating current effect the
physiology and behaviour of fishes in different
ways (Halsband, 1967; Lamarque, 1967). At
alternating current (Fig.2A) the electrodes con-
tinuously alternate as anode and cathode, mostly
at frequencies of 50 or 100 Hz (times per second)..
The fish is not attracted to either electrode. With
direct current (Fig. 2B-G) the electrodes are per-
manently anode or cathode resp., but a quantita-
tive change in voltage (regular or irregular) can be
created. The fish is attracted to the anode and
repelled by the cathode.
Either constant (Fig. 2D) or pulsed direct cur-
rent can be used. The possibilities of variation in
the pulse type are practically unlimited. The fre-
quency can be varied regularly (generally

SMALL ELECTRODE

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LARGE ELECTRODE

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1-100 Hz) or by a combination oflow frequency
pulses compiled of a number of high frequency
pulses (Fig. 2G). Moreover, the form of a single
pulse can be varied from a rectified sine pulse over
different forms of unregularly composed pulses
(e.g. condenser pulses) to e.g. rectangular pulses
(cfr. also Vi bert, 1967; Sternin et al., 1972).
Alternating current has a larger immobilization
zone than direct current. As, however, direct cur-
rent outside this zone has an attraction zone, the
fishing efficiency of direct current might surpass
that of alternating current (Fig. 4). Constant di-
rect current has a lower physiological effect than
any type of pulsed direct current as long as the
total energy input per time unit into the water is
equal (Vi bert, 1967; Sternin et at., 1972; Regis
etal., 1981; Hickley, 1985). The difference is
more pronounced when immobilizing than when

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DISTANCE

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Fig. 3, The attraction and immobilisation zone (schematic picture) when using small and large electrodes (in the latter case with
a higher current demand on the generator).

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