Smith-Root ELECTROFISHING BOATS, User Manual, Page: 48 / 53

46
2007
ELECTROfISHING
BOATS
ADJUSTING THE VOLTAGE
By adjusting the output voltage, the effects of the water’s
conductivity on electrofishing can be reduced.
The current flowing through the water is directly related
to the voltage applied. The higher the voltage, the greater
the current will be.
When adjusting the output voltage, the major
consideration is the power being used. This is especially
true for battery powered electrofishers. Power is equal
to the voltage multiplied by the current. When figuring
the power for an electrofisher, the fact that it is usually
putting out pulsed DC must be taken into consideration.
The instantaneous power during a pulse may be quite
high, but if the electrofisher is only producing pulses
at a 25% duty cycle, the average power would be
approximately 25% of the instantaneous power.
fIELD TECHNIqUES
An operator engaged in electrofishing must wade or
float, depending upon the depth and swiftness of the
water.
WADING
In shallow, slow-moving waters the operators can wade
and probe the anode into likely fish habitat. Wading
upstream eliminates the effects of turbidity caused by
bottom sediment. Furthermore, if collections are for food
habitat study, stunned prey are not swept downstream
and consumed by predators. Fish that manage to escape
are often captured a short distance downstream. Closing
a stream with seine nets at each end of the study area
helps prevent the loss of stunned and frightened fish.
BOATS
Boat electrofishers are used in lakes and in streams that
are too deep or swift to wade. Boats have the advantage
of being able to carry large generators and holding tanks
for the stunned fish. Electrofishing boats typically have
two insulated booms extending from the bow. From
the end of the booms electrodes hang into the water.
Usually one boom is used as the anode and the other
as the cathode. The boat operator guides the boat while
the electrofishing crew activates the electrofisher when
approaching likely habitat.
NIGHT fISHING
Electrofishing at night with lights is five to ten times
more effective than daytime fishing, especially in lakes.
In streams the reflection of the spotlight on the ruffled
surface makes the fish difficult to see. Boats have
floodlights on the bow to attract the fish and to help
locate stunned fish.
SURPRISE
Collecting can be enhanced by introducing the element
of surprise through intermittent fishing. The intensity of
the anode’s peripheral field often frightens fish, causing
them to bolt and hide. Do not work with the power on
continuously, but turn it on only in likely habitats. Fish
can be enticed from under areas of heavy cover or ice
by inserting a portable anode, turning the power on, and
withdrawing the anode slowly and smoothly. Fish will
follow the anode, under the influence of galvanotaxis,
into the open where they can be netted.
CLARITY AND DEPTH
Clarity of the water limits the ease of capturing fish.
The length of the dip net handles and the visibility of
the fish limit the depth of effective electrofishing. In
general, waters over ten feet deep cannot be sampled
effectively. For daytime fishing, polarized sunglasses
helps in locating stunned fish.
VEGETATION
Aquatic vegetation grows better from certain substrates
and can hinder electrofishing by fouling electrodes and
entangling stunned fish.
WATER VELOCITY
Electrofishing in flowing water is not as effective as in
still water, since fish are swept away from the electric
field and netting is more difficult. Also, it is more
difficult to see a fish in fast flowing water, and operators
can lose their footing. Flows greater than 5 feet per
second usually produce poor electrofishing efficiencies.