AN EXPERIMENTAL INVESTIGATION OF ELECTRIC FISH SENSORY AND DATA PROCESSING SYSTEMS DESIGNED TOWARD DEVELOPING PHYSICAL ANALOGS FOR HARDWARE PROTOTYPES HAVING SIMILAR CAPABILITIES

• Document Type: SPECIALCOLLECTION
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): 00173965
• Release Decision: RIPPUB
• Original Classification: U
• Document Page Count: 18
• Document Creation Date: January 21, 2025
• Document Release Date: January 15, 1983
• Publication Date: October 2, 1973

AN EXPERIMENTAL LNVESTIGATIbN OF
THE ELECTRIC FISH SENSORY AND DATA
PROCESSING SYSTEMS DESIGNED TOWARD
DEVELOPING PHYSICAL ANALOGS FOR
HARDWARE PROTOTYPES HAVING
SIMILAR CAPABILITIES ,
2 October 1973
Experiments Needed to Assess Sensitivity, Range and Effective-
ness of the Electric Fishes to Detect Objects and Communicate
Underwater
We consider it necessary to perform a number of experiments de-
signed to quantify some of the electric fish properties. Four different
species of electric fishes have been considered for these experiments be-
cause of their basically different SysterriS used as transmitters and electro-
receptors. These fishes are:
a. Gymnarchus niloticus
-An African weakly fresh-water electric fish with a medium. .
fixed frequency(260 to 300 Hz) and a Composite waveform. .FreqUency.
does not change with ternp:rature. It has about seven kinds .of electro-
rebeptors plus displacement, acoustic and chemical sensors located on
or near the skin. Electroreceptors are located on the whole body but are
more numerous near and on the head and near its ver:y- pointed tail.
Countries or origin Sudan, Nigeria and Ivory Coast and the two Congos
of Africa. It can grow to a maximum size of 5 feet and has a life span of
about 40 years.
The electric organ is located caudally occupying about 1/2
to 2/3 of the fish length. Electric organ is derived from modified
muscle spindels. Difficult to obtain and to keep alive. Has strange
parasitic diseases affecting the spinal cord. The fish is blind and has
only vestigial eyes.
b. Sternarchus albifrons
A South-American weakly fresh-water electric fish with a
high, relatively fixed frequency (700-800 kHz) and a composite waveform.
The rate of discharge is temperature dependent at a rate of between 40
to 60 Hz per degree centigrade. Has at least three kinds of electro-
receptors plus displacement, acoustic and chemical sensors located on
or near the skin. Electroreceptors are located on the whole body and
.
preferentially on or around the head. Counties of origin: Brazil,
Columbia, Venezuela, Guyanas, Argentina, Bolivia, Ecuador, Peru
in South-America and some parts of Central America. Can grow to a
maximum size of one foot. Life span is at least 10 years.
The electric organ is located candally occupying about 2/3
of the fishs' body length. The electric organ is derived from modified
nervous tissue. It is a hardy species, easy to maintain and easy to
procure. This fish is also blind and has vestigial eyes.
c. Gymnotus carapo
A South-American weakly fresh water electric fish with a
medium� low variable frequency (30 to 150 Hz) and a composite wave-
form. Has multiple electro and sensory receptors located on or near
the skin. Electroreceptors are located on the whole body and preferenti-
ally on or near the head. Counties of origin same as for Sternarchus
albifrons. Can grow to a maximum size of one and a half feet. Life
span is several years.
The electric organ is located caudally occupying about 1/2
of the fishsi body length. The electric organ is derived from modified
muscle spindels. It is a hardy species but is not as easy to procure as
Sternarchus.
d. Gnathonemus petersii
An African weakly fresh-water electric fish with a low variable
pulse-form repetition rate signal (5 to 170 pps). Has multiple ampulla.ry
and tuberous electroreceptors and sensory receptors located on the body
2
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and preferentially on or near the head. Counties of origin located in the
subtropical, tropical and equatorial Africa. Can grow to a maximum size
of one foot. Life span may be several years.
The electric organ is located in the tail and is derived from
modified muscle tissue. (It is relatively easy to procure, but is very
difficult to maintain it alive for longer periods of time in captivity.)
For all experiments we will use a fiberglass water tank of 12 ft
diameter and 4 ft height.
Experiment #1(B)
This experiment is designed to establish the ability of an electric
fish of the species mentioned under (a) and (b) to detect metallic or non-
metallic objects having different masses and introduced in the water tank
at different distances from the fish. The fish will be held in a position A
by a vertical nylon net. The nylon-net will be raised and the object intro-
duced at position B. The time until the fish will detect the object will be
noted by observing the fish which may retract or advance in the direction
of the object, depending on the composition and mass of the object and on
the species of the fish. This experiment will be repeated after lining the
interior of the tank with aluminum foil (see Fig. 1). The objects con-
sidered are: iron, stainless steel (non-magnetic), wood, plexiglass,
each in different dimensions (like 10 cm x 2 cm; 5 cm x 1 cm; 2 cm x
0. 5 cm; etc). The objects will be fixed to a nylon thread and introduced
vertically into the tank.
Experiment #2 (B)
This experiment is designed to assess the capability of electric
fishes to use their navigation system to avoid obstacles like fine nylon
Electric Fish Position "A"
/Nylon Net
(Can be moved vertically)
Water Tank
12 ft 6 and 4 ft high
made of fiberglass
Object to be Introduced
Position "B"
Fig. 1. The reaction time of the fish will be plotted
against different masses of the same material
type of object and for the same mass of dif-
ferent kind of object materials. A short film
may be made to illustrate the reaction of the
fish.
thread or fine wire (aluminum); copper cannot be used because copper
even in minute quantities will kill these fishes. Again we will use fishes
of the species mentioned under (a) and (b). Gymnarchus niloticus is an
air breather and cannot be confined in a tube but it can be used in experi-
ments with free swimming fishes. It is also a small goldfish eater. This
fish will be put in the tank at the point "A" (see Fig. 2) behind a nylon net.
A double net will divide the tank. A goldfish will be put in a nylon net bag
and introduced in the tank at point "B" after the nylon net holding the
electric fish has been removed. The reaction of the fish and the avoidance
of the net will be observed and filmed. The fish species type (b) Stern-
archus albifrons is not a fish eater but usually reacts with an escape to a
metallic object. In this case a metallic object will be used to force the
fish to cross the double net. Its avoidance of the obstacles will be noted
and filmed. Both fishes are blind.
The experiment will be repeated using a grounded aluminum foil
along the inner wall of the water tank.
Experiment #3 (B)
This experiment is designed to demonstrate the ability of electric
fish to detect a magnetostatic field. The arrangement will be similar with
experiment #1 but instead of using an object in the water we will use a
permanent magnet outside the tank. Magnets of 10 kG, 1 kG, and 500 G,
will be used at distances of 3 ft from the tank wall or near the tank wall
at Position "B" or "C". The fish will be located at position "A" behind
a nylon net (see Fig. 3). The magnetic field in the tank will be measured
with a Hall-effect-probe and a Gaussmeter. The reaction of the fish to
the magnetic field will be noted and filmed. The threshold of detection of
Eventual direction of
fish moving toward the
prey at "B"
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Electric Fish
Position "A"
Nylon Net (Can be removed)
AM.� ������ IN�1�1. .1111M
Figure 2.
Water Tank
Fiberglass 12ft c x 4 ft
Nylon Nets
Nylon Bag
Gold Fish
Position "B"
1 11 11 III 11 ill 11111
Position of Wire Nets
6
the magnetic field by different fishes of the same species and of the
average of different species will be plotted one against each other. The
magnet will be also moved from "D" to "E" and the reaction of the fish
observed.
Direction of
Movement
Position
Position "C'
lectric Fish Position "A"
Figure 3.
Nylon Net
Fiberglass Water Tank
12 ft Q x 4 ft high
Permanent Magnet
The sensitivity of electroreceptors will be calculated, counting
the number of electroreceptors per square cm and plotting it against the
minimum magnetic field gradient that could be detected by the fish.
7
Experiment #4 (B)
This experiment is designed to demonstrate the ability of electric
fishes to detect electrostatic fields. The arrangement for this experiment
will be similar to the preceding experiment, #3, but instead of a permanent
magnet we will use a sphere charged electrostatically to 100, 200, 400,
and 1000 ESU and isolated on a teflon and plexiglass support. The gradient
of the field generated by the charged sphere in the tank will be calculated.
The threshold of reaction of the electric fishes (different fishes of the same
species and different species) will be established (see Fig. 4).
Electric Fish Position "A"
you
Direction of
Movement
Position "B"
Position "C"
Figure 4.
8
Nylon Net
Fiberglass Water Tank
12 ft 4) x 4 ft high
0
Electrostatically
Charged Sphere
The threshold of detection of the electrostatic field (stationary or
moving) of different fishes of the same species against each other and the
average of different species against each other will be plotted. The sen-
sitivity of the electroreceptors will be calculated, counting the number of
electroreceptors per square cm and plotting it against the minimum electro-
static field gradient that could be detected by the fish.
Experiment #5 (B)
This experiment is designed to assess the ability of electric fish
to detect DC, AC repetitive signals, square wave and transient signals.
The fish will be positioned behind a nylon net in the tank. Carbon elect-
rodes will be put in the tank at the opposite end of the tank at one feet
apart (see Fig. 5). The four experiments to be performed are as follows:
a. DC signals will be applied with a telegraph key monitored by
an oscilloscope and attenuated by potentimeter and furnished by DC bat-
teries. A resistance in series will limit the current (see Fig. 6). The
reaction and threshold detection of the electric fish of the applied current/
and voltage will be noted. The gradient of the current will be calculated
and a measurement of the voltage at the position where the fish will be put
will be made prior to putting the fish in the tank with two carbon electrodes
one foot apart. The threshold detection of the different fishes of the same
species will be plotted one against another and the average of different
species will be plotted also each against another.
b. The same procedure will be used to find the threshold of de-
tection of AC sinusoidal current for frequencies of 5, 10, 20, 50, 100, 200,
500, 1000, 2000, 5000, and 10,000 Hz (see Fig. 7). The signals will be ap-
plied with nonpolarizable Ag,AgC1 electrodes and measured with the same
kind of electrodes. Also frequencies close to the fishes own frequency will
be used.
9
c. Square waves of same repetition rate as the sinusoidal currents
will be used and applied with Ag, AgC1 electrodes.
d. The transients will be applied with the help of a network using
a pulse transformer, resistors and a charged capacitor (see Fig. 8). The
values will be calculated and the resulting waveforms will be measured
with an oscilloscope. These signals will be applied also with Ag, AgC1
electrodes.
The reaction and threshold of detection of the signals will be
noted and plotted the same way as for DC current.
Fiberglass Water Electrodes for measurement
Tank of applied current attenuated
12 ft t!) x 4 ft high by the water in the tank
Electrodes for
Applying Different Currents
and Signals
Figure 5.
10
Shield ---or
�������������
R2
10�������
����
�
Shielded Cable
Carbon Electrodes
1 ft apart 1 cm free ends
Oscilloscope
B = Battery (optimum voltage will be determined by experi-
ments but tentatively set between 2 and 6 volts)
P1' P2' P3 = Potentiometers calculated to have constant impedance
together with Ri = resistor to correspond to the im-
pedance of the carbon electrodes in water measured
with the AC liquid impedance bridge
C and R2 = capacitor and resistor to suppress sparks when the
key is manipulated
k = key (telegraph type)
Fig. 6. DC signal system.
11
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���
Transmitting Electrodes
in the Water
Ag, AgC1
Waveform Impedance
Generator Adapter
Oscilloscope
Receiving Electrodes
in the Water
Ag, AgC1
Oscilloscope
Fig. 7. Set-up for sinusoidal AC and square waves.
To battery +
for charging
the capacitor
0
-L C2
� _ _4 _
4��������
Shield
Shielded Cable
Ag, AgC1 Electrode.
in Water
Oscilloscope
C1 = High capacity tantalitic capacitor (value to be experi-
mentally established according to the impedance of the
electrodes in the water)
C2R3; C3R4 =
R1' R2 =
Spark suppressing networks
Variabl resistors to adapt the circuit to the Ag-AgC1
electrodes in the water
J = Jack for peak current measurement (with a resistor
in series and an oscilloscope in parallel)
T1 = Pulse transformer
Fig. 8. Transient generating set-up.
13
77.-r
Irv., "Err 7
Experiments #1(P), 3(P), 4(P), and 5(P)
These experiments will be similar to the experiments 1(B), 3(B), 4(B) z
5B but instead of using free swimming fishes we will use fishes of species
mentioned in "C" and "D" on page 2 like Gymnotus carapo and Gnothonemus
peters ii or equivalents restrained in a plexiglass tube with holes and two
stainless steel electrodes at the end (see Fig. 9). Instead of observing the
reaction of the electric fish to the different stimuli, we will monitor on the
oscilloscope and frequency counter the charging rate, amplitude and wave-
form of the fish response to the stimuli. The latency and habituation will
be noted. This time the graphs will show the relation between stimulus and
response and also the threshold of reaction. With this species of fish and
system a better quantification is possible of the ability of fish to detect ob-
jects, magnetic fields, electrostatic fields, DC currents, AC repetitive
sinusoidal or squarewave signals and transient signals.
Oscilloscope
amommom.
Amplifier
Frequency
Center
Object to be
detected,
Experiment # 1(P)
Electrostatically charged sphere,
Experiment # 4(P)
Figure 9.
>_Plexiglass tube
with fish in it
and electrodes
at the end
-.. Fiberglass
As' Water Tank
12 ft 4 x 4 ft high
1
Electrodes for Experiment *5(P,
Permanent magnet,
Experiment #3(P)
14
Experiment #6
This experiment is designed to relate the ability of electric fishes
to communicate underwater and the distance at which they can manage it
(see Fig. 10). The natural noise and the signal strength of the fish will
be measured. The original signal will be recorded with electrodes on a
magnetic tape recorder and monitored on an oscilloscope. This signal
will be played back with the aid of two carbon electrodes in the tank at a
place "f" at the distance "1" from the fish situated at the point "g" and
confined there with a nylon net. The reaction of the fish to its own signal
will be observed and eventually filmed. The signal will be subsequently
attenuated to precalculated attenuations corresponding to distances of 100 It,
500 ft, 1000 ft and 5000 ft. lithe fish will not react to a certain attenuation
a variable attenuation in between the fixed points will be used to assess the
distance at which the fish can detect its own signal. Also later noise will
be introduced in the form of white noise and its effect on the ability of the
fish to detect its own signal will be observed. At the end graphs will be
plotted for the signal to noise ratio versus distance of signal detection.
The field generated by the electric fish will be calculated and
plotted on a graph.
The experiments #113, 213, and 38 will be made in the fiberglass tank
as it is and with aluminum foil set around the inner wall of the tank and
grounded. The results with or without the grounded aluminum-foil will
be plotted on graphs and eventually graphs will be plotted for the differ-
ences in results with and without grounded aluminum foil.
15
Amplifier
Oscilloscope
Oscilloscope
Receiving Electrodes
Ag, AgC1
Nylon Net
Fiberglass Water Tank
12 ft (1) x 4 ft high
Transmitting Electrodes
Ag, AgC1
Impedance Amplifier FM Tape Recorder
Network Electric Fish Position G
)f;5. Nylon Net
Oscilloscope
Fiberglass Water Tank
12 ft (t) x 4 ft high
Transmitting Electrodes
Ag, AgC1, Position E
Impedance Amplifier FM Tape Recorder
Network
Figure 10.
16
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Experiment #7
In this experiment the electromagnetic field around some electric
fishes (the ones which can be confined in a tube) will be measured and �
compared with values resulting from the calculated field.
Electric Fish
Ag, AgC1 Electrodes
Amplifier
Oscilthscope
Amplifier
Oscilloscope
Figure 11.
17
Electrodes Ag, AgC1
Moved in the Direction
to the Center