Our electrofishing (“shocking”) sampling is performed with a boat-mounted, pulsed-DC system.  We use a specially-wound generator that's connected to a control box, which is connected to two booms with anode (positive) arrays attached to each end.  The aluminum boat hull serves as the cathode (negative).  The electric current produced by the electrofisher stuns scaled fish within a 5- to 10-ft radius of the anodes, depending on conditions.  Fish are dipped up with a net and placed in an aerated livewell.  The fish normally recover within a few minutes. 

The electrofishing is usually done around shoreline cover, such as stumps, logs, vegetation, or other likely areas.  A timer on the control box measures the actual length of time that an electric current is produced.  After every 15 minutes or so of actual shock time, the fish are weighed, measured, and released.  The total amount of sampling time depends on the size and shape of the lake.

The data are used to calculate the following information:

• Catch Rates—the number of fish per hour

• Length Distributions—the number of fish in each inch group

• Relative Weights—somewhat similar to the body mass index used in human medicine

• Stock Density Indices—simply put, the percentages of fish larger than certain sizes

This information can be used as a snapshot of the current fish populations.  Questions such as, “Are my fish getting enough to eat?”, “Are undesirable fish present?”, and “Are my fish overcrowded?” can be answered.  Management recommendations—based on your objectives—can then be developed.

Contrary to popular belief, electrofishing doesn’t sterilize fish, and when done properly it’s virtually harmless to fish.  In fact, as part of his thesis research, Dave Hickman used a similar electrofisher to capture 48 largemouth bass.  The fish were held in net pens for two weeks to assess mortality.  Even though the experiment was carried out during the hottest part of the summer—normally when fish mortality is highest—none of the bass died!  Although some smaller or already stressed fish may be killed occasionally during routine sampling, electrofishing is generally harmless to the overall population.