7116 ‎(2)‎

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

pulse. The shape of electrodes determines the field
strength.
The power unit produces the energy required,
which increases with the conductivity of the
water. At low conductivity ( < 75 jlS) the voltage
needed is acquired with an effect ofless than 1 kW
and both batteries and generators can be used. At
higher conductivities batteries are too rapidly dis-
charged and stronger power units must be used.
At 500 jlS the effect required is approximately
2 kW and in marine environments 5-10 kW (cfr.
Hickley, 1985). Such devices are heavy but could
be used for electric fishing as long as suitable
means of transportation are available (Vibert,
1967; Sternin etal., 1972; Weiss, 1972, 1976;
Dembinski & Korycka, 1974; Cross, 1976;

+

w
~
c( 0
I-
...J
o
>

A. AL TERNA TlNG CURRENT

]

D. CONSTANT DIRECT
CURRENT

+-

n

o

G. COMBINED FREQUENCY
CURRENT

11

Lamarque, 1977 ; Phillips & Scolara, 1980;
Heidinger et al., 1983). Even at conductivities
typical for eutrophic lakes the effect needed
causes problems with respect to weight and size
of the power unit. Especially in this type of water,
it is therefore essential to optimize the efficiency
of transformers and electrodes. Most power units
produce 2-phase alternating current, converted
into some kind of direct current by a transformer.
When using electronic devices high frequency
ripple might arise, which may lower the efficiency
(Priegel & Novotny, 1975). With other types of
equipment a certain degree of pulse might remain
when transforming to direct non pulsed current
(Hartley, 1980). In the first case an electric filter
could be used to reduce the ripple, while in the

B. RECTIFIED AL TERNA TING
CURRENT

C. HALF- WAVE
RECTIFED CURRENT

Jnnn_ J~~~

E. SQUARE WAVE
CURRENT

Fig. 2. Different shapes of current.

F. CONDENSATOR
DISCHARGES