Smith-Root GPP 2.5 - Field Techniques

23
USER’S MANUAL
www.smith-root.com
SURPRISE
Collecting can be enhanced by introducing the element
of surprise through intermittent shing. The intensity of
the anode’s peripheral eld often frightens sh, 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 inuence of galvanotaxis, into
the open where they can be netted.
CLARITY AND DEPTH
Clarity of the water limits the ease of capturing sh. The
length of the dip net handles and the visibility of the sh
limit the depth of effective electrofishing. In general,
waters over ten feet deep cannot be sampled effectively.
For daytime shing polarized sunglasses help in locating
stunned sh.
VEGETATION
Aquatic vegetation grows better from certain substrates
and can hinder electrofishing by fouling electrodes and
entangling stunned sh.
WATER VELOCITY
Electrofishing in flowing water is not as effective as in
still water, since sh are swept away from the electric eld
and netting is more difcult. Also, it is more difcult to
see a sh in fast owing water, and operators can loose
their footing. Flows greater than 5 feet per second usually
produce poor electroshing efciencies.
FIELD TECHNIQUES
An operator engaged in electroshing must wade or oat,
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 sh.
BOATS
Boat electroshers 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 sh. Electroshing 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 electroshing crew
activates the electrosher when approaching likely habitat.
NIGHT FISHING
Electroshing at night with lights is ve to ten times more
effective than daytime fishing, especially in lakes. In
streams the reection of the spotlight on the rufed surface
makes the sh difcult to see. Boats have ood lights on
the bow to attract the sh and to help locate stunned sh.
INTRODUCTION TO ELECTROFISHING