A crank magneto from an old telephone and some 10-gauge insulated electrical wire are all of the materials that are needed to build a fish shocker for electrofishing. Virtually any direct current power supply source with ample voltage output or an alternating current supply with a voltage inverter can be rigged with a cathode and anode to be used for electrofishing. A safe method of administering the shock and retrieving the stunned fish is also highly recommended.
Strip a few inches of insulation off of each end of two 15-foot lengths of 10-gauge electrical wire. Attach the end of one wire to the positive terminal on the crank magneto, and attach one end of the other wire to the negative terminal. Place the other end of the wires into the water, and crank the magneto to shock the fish in the surrounding area. Users must be in a safe location insulated from electricity, such as on shore, in a wooden boat or wearing rubber waders, before turning the crank. A fishing net or dip-net is needed to recover the fish floating on the surface.
Other possible options for construction of a fish shocker include using a cathode and diode mounted directly onto a fishing dip-net rim, as long as the handle of the net is insulated.