Electrofishing

Electrofishing is perhaps the most commonly used tool by fish managers and researchers to capture fish.  It involves passing an electric current through the water, which causes fish to involuntarily swim towards an electrode where they are netted.  Fish can then be counted, measured or examined (depending on the objectives of the study) and returned to the water unharmed.  Electrofishing has been a common fisheries tool for the past half-century, in Wyoming and throughout the United States.  

Through the years, the Wyoming Game and Fish Department has developed and refined numerous gears to allow safe electrofishing in a wide range of habitats for a variety of species.  Electrofishing systems used in Wyoming include backpacks, shore-based units, cataraft or barge units, rafts, and jet outboard powered boats.  Although the systems may differ, they involve the same basic components.  These components include a power source (generator or battery), a control box that creates the correct waveform to safely stun fish, an anode (positive electrode) and a cathode (negative electrode).  

Backpack electrofishing units are one of the most widely used electrofishing systems in Wyoming.  They are generally used on small streams that are easily waded.  The entire system is mounted on a backpack frame worn by the operator.  Power is supplied by either a small generator or battery, the cathode is usually a cable trailing behind the unit, and the anode consists of a probe manipulated by the operator to stun fish.

A shore-based electrofishing unit is often used in medium-sized streams and can produce more power in the water than a backpack unit.  This additional power is often necessary in streams where the conductivity of the water is either too high or too low to electrofish efficiently.  A shore-based unit consists of a generator and control box situated on the shore.  A long extension cord (usually 100-200 yards long) carries the power to anodes that are carried by one or more operators.  The cathode consists of a rod driven into the streambed that is attached to the control box.

Sometimes a stream is too deep to safely wade, or personnel wish to sample a reach that is longer than a shore-based unit will allow.  In these situations, a barge unit is often used.  A barge unit consists of a barge (or cataraft) that carries the generator, control box and tub to place fish in.  Multiple anodes extend off the craft that can be used by operators to capture fish.  Catarafts have been shown to be the best “barge” for Wyoming waters.  They ride very high on the water and are easy to pull and maneuver in high velocity streams common to Wyoming.  

When wading isn’t possible, raft or boat electrofishing units are used.  These units are equipped with anodes mounted on booms extending in front of the craft.  The vessel is maneuvered to position the anodes in fish habitat and one or two netters in the bow net stunned fish.  These boats are very effective in collecting trout, and are used to conduct trout population estimates in large rivers in Wyoming.