7116 ‎(2)‎

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

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Fig. 5. Efficiency of direct versus pulsed current for immobilisation of fish (] indicates equal efficiency) at different duty cycles
(frequency x pulse length).

Detailed studies of the relation between electrode
size and fishing efficiency have been performed by
Cuinat (1967) and Sternin et al. (1972). Large
sized electrodes result in increased fishing effi-
ciency and reduced fish mortality. The latter is an
effect of the negative correlation between anode
size and current line density (voltage gradient) in
the water close to the electrode (Fig. 3). An
increase of the anode diameter from IOta 60 cm
results in a three fold increase in the effective
fishing area, while the maximum current line den-
sity is reduced from 40 to 17 V / cm (Cuinat, 1967).
Alternatively the same fishing area would be
achieved if the energy input was reduced from 5.9
to 2.7 kW (at 2700 J1.S), while the anode diameter
was increased.
The area of the cathode should be as large as
possible and at least 3 times as large as the anode,
In commercial fisheries the boat itself often serves
as cathode. The upper size limit of the electrodes
is mainly (especially for the anode) restricted by

manageability. In most cases an anode diameter
of 40-60 cm is therefore the optimal solution.
When a larger size is needed two anodes could be
connected in parallel. The benefit of increasing
cathode size is less pronounced at large sizes.
On theoretical basis Sternin et al. (1972) recom-
mends spherical anodes, but Cuinat (1967) found
only small efficiency differences between spheri-
cal and circular anodes when testing this empiri-
cally. Both anodes and cathodes could be shaped
as rings or nets. Chicken wire is recommended as
a cheap and light material for the cathode (Cuinat,
1967).
The corrosion of the material is mainly caused
by electrolysis. When using direct current only the
anode is affected. Corrosion increases with the
energy output and is therefore mainly a problem
at medium and high conductivities. The corrosion
properties of different materials is expressed by
the corrosion coefficient, which can be found in
appropriate literature. Materials like chromium-

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