7124

• UCREFRP Catalog Number: 7124
• Author: McAda, C. W. and R. S. Wydoski.
• Title: Technical Papers
• USFW Year: 1980.
• USFW - Doc Type: \
• Copyright Material: YES

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Comparative Evaluation of the Repellent and Attractive
Effects of Electrical and Acoustic Fields for the

Baltic Herring, Clupea harengus membras

Institute of

N.A. Stepanova

E\olutionary Morphology and
IEMEZH, Moscow

Ecology of Animals -

The effect of an acoustic field, a pulsed electric field and
both fields on a school of Baltic herring, CZupea harengus membras,
was studied.

The effects of physical fields on fish have been studied since the late nine-
teenth century,. The first studies, (Du Bous-Reymond, 1887; Fritsch, 1890) were
P?rely descriptive. intended primarily to explain the mechanism by which physical
f1elds acted on fish and the corresponding physiological changes which occurred.
Subsequent studies using precise, reproducible measurements have revealed a number
of relationships between field parameters and the physiological state of the fish
and have led to attempts to use physical fields in commercial fishing (Mironov,
1948; Gyul'badomov, 1958; Shentyakov, 1964; Nikonorov, 1968; Shishkova, 1977;
Trakis, Danyulite, 1977; Olsen, 1976), The decrease in motor activity of fish
caused by an electric. field can be used during trawling to prevent fish'from leav-
ing the trawl zone (Titov, Mal 'kyavichus , 1969; Lamargue, 1975). The depressive
reaction or electronarcosis is used in this case, Interesting experiments by
Norwegian scientists (Olsen, 1976) have demo~strated controlled behavior in CZupea
~engus and rhe development of conditioned reflexes to sound among PoZZachius
V1.1'en8 by emitting sound during feeding, with the goal of creating and maintaining
commercial concentrations. of fish in selected areas.

The. future development of mariculture as a new'branch of the world fishing in-
dustry (Priss, 1976) will require new biotechnical approaches and equipment for
artificial concentrations of fish, holding them in littoral areas, and herding them
.into estuaries and bays~ As marine fish farming develops, judging from results
achieved to date, phy~ical fields will be widely used,

For the first'stage Of our . studies we determined the electrical and acoustical
field parameters which first cause a reaction in schools of fish, and also studied
the possibility of reducing the threshold of sensibility of schools to electric
current by the combined use of an acoustical field. The final purpose of this
stage of our study was to select the minimum parameters of the fields with com-
mercial potential for subsequent fiShing studies: herding of fish into traps and
holding of fish in catch areas,

The object of the
bras, 15 cm specimens
in groups of 50 to 80
x25x5 m) of seawater,

investigation was the Baltic herring, CZupea harengus mem-
were caught with fixed nets in the Baltic Sea and transferred
specimens to a holding net (10x8xO,5 m) in a large pool (250x
Freshly caught fish were used in each series of experiments,

The electric: field was created' by a type IG pulse generator, producing a uni-
polar pulsed current up to 150 Hz of pulse length 0.12 to 2 ms, voltage at generator
output 10 to 300 V, The basic pulse shape was semisinusoidal, attenuation factor
l(z(),3-1.2,

}34

The entire volume of the experimental holding net was divided into a number of
arbitrary sections, their number determined experimentally depending on the direc-
tionality of the fields generated, The electric field intensity was measured at
the center of each grid cell (lxlxO.25 m) using a three dimensional transducer.
Coefficients were then calculated to determine the field attenuation in the space
around the electrode, After the field intensity diagrams were constructed we noted
the areas of greatest and least variation. These data were entered on a plan,
giving us a clear picture of the electric field within the net. Later comparison
of this plan with diagrams showing the reaction of schools of fish in the net al-
lowed us to determine the behavioral reaction threshold (movement to the area with
minimum field intensity, changes in direction of movement, dispersal of the school,
etc.).

The acoustical field was produced by an electrodynamic generator with an out-
put power of 25 V contained in a sealed hemisphere. The generator generated a
sound pressure of P=8.102 Pa in the frequency range of 50 to 300 Hz at a distance of
1 m. We also used a "pilot whale" piezoelectric generator with a power of 50 W,
sound pressure 2,5.102 Pa in the 200 to 8,000 Hz frequency band (measurements pro-
vided by hydroacoustical instruments laboratory, National Scientific Research
Institute of Marine Fishing and Oceanography). The sound generators were placed at
the ends of the holding net. Acoustical field measurements were performed at the
same points in the net as the electrical field measurements, measuring both sound
pressure and noise level, The number of herring used in each experiment was
minimized to reduce the sound field distortions caused by the fishes' bodies to al-
low more accurate observation of,the fishes' reactions in the net.

Experiments on (~rding of fish into traps-were performed in an open pool mea-
suring 250x25x5 m, Two piezoelectric generators and a system of electrodes cover-
ing the cross section of the pool were mounted on a bream carried along the pool on
rails. The trap was located at the end of the pool.

An electric "field, acoustic field or combined field with various parameters
was produced in the water by the equipment on the bream, and moved through the wa-
ter as the bream moved along the pool, herding the fish toward the trap. The num-
ber of herring caught in the trap was used to judge the effectiveness of various
fields,

The results of preliminary experiments prompted us to use a pulsed current with
the following parameters: pulse repetition frequency f=20 Hz; pulse length T=
=1.5'10-3 s; generator output voltage U=87 V. plus the "pilot whale" pulsed sound
with a maximum sound pressure at 1 m from the generator and 2 m from the water
surface of 25.102 Pa, noise level .4.2'10-7.0'10 Pa.

Each series of experiments involved 3 movement speeds (V) of the bream, 0.15,
0.25 and 0.5 m/s. The following sequence was used: a) electric current; b) sound;
c) current and sound (repeated five times). Forty-five experiments were performed
in each series, Before changing the speed. the effect of the bream with all equip-
ment attached but with the field generators turned off was tested.

Experiments on holding fish in the catch zone were performed on Baltic herring
in an open area of the Baltic Sea from a research vessel. The experimental in-
stallation consisted of two metal frames (3x2 m) connected by flexible couplings
(0.5 m), Enough floats were attached to one of the frames to hold both of them on
the surface of the water. A net bag was attached to the bottom frame. Rings were
attached to the corners of the top frame, through which flexible lines were passed
which were connected to the bottom frame. This allowed the bottom frame to be
raised rapidly to the top frame. The two frames were equipped with electrodes at-
tached to the ship's generator bya power supply cable. Two sound generators were
also attached to the bottom frame. The installation could create an electric field
around the perimeter plus an acoustic field through the entire volume enclosed by
the frames. Before beginning each experiment at least 10 fish were placed in the
net bag, Each series of experiments consisted of 10 repetitions. After the fish
became quiet the net bag was lowered and the barrier (current or current and sound

135