Smith-Root ELECTROFISHING BOATS, Руководство пользователя, Страница: 47 / 53

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USER'S MANUAL
ELECTROfISHING PRINCIPLES
LOW CONDUCTIVITY WATER
Distilled water is a very good insulator. It has a
conductivity range of 0.5 to 5.0 microSiemens/cc. If a
normal voltage is applied in distilled water, very little
current will flow. Power flow is too low to be effective
for electrofishing.
The current passing through a fish decreases as the
power flow decreases. To get the same response from
fish, the current can be maintained by either increasing
the voltage, or by keeping the resistance low.
If a higher voltage is used, up to 1,200 volts may be
necessary. High voltages create three problems: special
electrical equipment is required, safety is reduced for
the operators and conditions are lethal for fish close to
electrodes.
The resistance can be kept low by increasing the size
of the electrodes. The only limitations to this are the
availability of larger electrodes, and the weight of
electrode that can be handled by the operator.
HIGH CONDUCTIVITY WATER
High conductivity is over 2,000 microSiemens/cc. If a
high voltage is applied, most current will flow easily
through the water and the fish will hardly be affected.
The electric current follows the path of least resistance
and bypasses the fish completely. Therefore, use low
voltages and high currents. Currents as high as 60 amps
are common, the limiting factor being the rating of the
power-supply.
Some brackish water and industrial waste water have
conductivities over 10,000 microSiemens per centimeter.
Here smaller power-supplies are unable to deliver
enough power to stun fish. Waters in this range can only
be electrofished effectively with the larger model GPPs.
The Smith-Root 7.5 GPP outputs 62 amps through 8
gauge stranded cables. This unit can stun large fish in
the interface between fresh and salt water. For example,
Striped Bass can be stunned for taking brood stock.
Theoretically, high conductivity could be dealt with
by using smaller electrodes, but this would reduce the
range and also create damaging current densities near
the anode.
fISH CONDUCTIVITY
A fish will receive the maximum shock through its body
when the conductivity of the water is the same as the
conductivity of the fish’s flesh. Unfortunately, this is
rarely the case.
Fish flesh conductivity ranges from 500 to 1,500
microSiemens per centimeter. Each species has a
different conductivity. This affects their susceptibility to
electric current.
Con ductivities for some fish species are:
Trout 1,220 microSiemens/centimeter
Perch 1,089 microSiemens/centimeter
Carp 870 microSiemens/centimeter
Grudgeon 814 microSiemens/centimeter
E. Halsband - Vilbert 1967
fISH SIzE
Among fish of the same species, the larger fish are more
sensitive to electrical currents. Fish absorb power as
a function of body surface area. This is important to
remember if you are shocking for small fish and large
fish are also present. The large fish are going to receive a
much greater shock than the small fish.
TEMPERATURE
Water conductivity and effective fish conductivity
increase with higher temperature.
Con ductivities reported for Carp:
5° 372 microSiemens/centimeter
10° 543 microSiemens/centimeter
15° 714 microSiemens/centimeter
20° 1,026 microSiemens/centimeter
25° 1,969 microSiemens/centimeter
Whitney and Pierce 1957
SUBSTRATE
Certain bottom substrates will conduct electrical current.
These weaken the electric field in the water, making fish
capture less effective.