What is electrofishing?

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How is electrofishing carried out, and is it safe for the fish?

Electrofishing is a technique commonly used by scientists and fisheries biologists to survey rivers and assess what fish are present. When done properly, it stuns fish for a short period allowing them to be removed carefully with a net, examined and then returned alive with no permanent harm done.

The device used, called an electrofisher, is often mounted in a backpack and uses two electrodes – an anode and a cathode – to deliver a high voltage charge into the water.  People doing electrofishing wear rubber waders to prevent zapping themselves.

When the electrofisher is triggered near a fish it is affected by the electricity and undergoes an uncontrolled muscular spasm called a convulsion which causes the fish to swim towards the ring-shaped, pole-mounted anode. This trait is known as galvanotaxis.

Electrofishing is a two man job, so one person discharges the electrofisher while another holds a net near the anode to catch the stricken fish. The scientists can then collect the fish, weigh or measure them and then return them to the river unscathed.

This item was first published in the November 2009 issue of Practical Fishkeeping. It may not be reproduced without written permission.