Many folks ask us about the electrofishing boat and how it works. Our boat is a 16 ft X 48 in flat bottom Jon boat with a 40 hp motor. On our rig the boat itself is the ground and the booms sticking out the front with the stainless steel droppers are the positive. Some rigs use separate cables for the ground, but by using the boat, you produce a better field. The boat has a padded railing around the front deck so we can lean out and dip and not fall in. Some shocker boats have lights on them for sampling at night. Our generator puts out up to 7500 watts, up to 1000 volts, various pulses (7.5-120 per second) and amperage, and is all controlled by the Shocker Box. The settings we use depend on the objectives for sampling, the water’s conductivity and species of fish being targeted. There is a peddle, that when pushed, puts electricity into the water and a timer that keeps track of seconds sampled, which we convert into a fish per minute index. The range and depth fish are affected depends on fish species, size and water conductivity. In some waterbodies fish need to be within three feet of the outside of boom and less than four feet deep. Other times fish are stunned as far as 15 feet outside the booms, and greater than 10 feet below the surface. Some fish are completely stunned and easy to dip, while others fight the electricity and can be very difficult and impossible to dip. Research has shown approximately 0.5 % of the fish shocked die, and generally those are fingerlings and fry. All remaining fish wake up and swim away unharmed. After we dip the fish they are placed into an aerated tank, sometimes with salt, until measured, weighed and then released. After each sample the tank water is pumped out and refilled. The water temperature can rise in the tank when jammed with fish, or from the sun, fish deposit waste and some regurgitate the most recent meal in the tank is why it is changed so frequently. Generally larger fish get hit harder (shocked) than smaller ones as they have more surface area to transmit electricity and occasionally take longer to wake up. Most fish by the time we measure and weigh are eagerly ready to swim away. No one has ever been killed as far as I know from electrofishing, but if you touch the water and the boat simultaneously when the peddle is down, you will feel it. If the water is highly conductive, the shock is very mild, but if the water is very soft and has very low conductivity the volts are high, even though the amps produced are low, and you will really feel it. We always wear rubber soled shoes and the deck and in front of the driver’s seat has a rubber mat for additional insulation. Sometimes we use one dipper and sometimes two. The driver always wears ear protection and sometimes the dippers too, and we use 6-8 ft long handle dip nets. If we are targeting catfish, the net webbing may be rubber to eliminate their spines getting tangled in the traditional green nylon nets.
The shocker can affect turtles, snakes, alligators, birds and even manatees. If we encounter a non fish animal, we simply release the peddle and allow it to get away and we resume. The larger the lizards, the more thrashing they do. I have seen them up to about 12 feet get shocked and those are dangerous that close, especially to the driver. Gators have a tendency to try and climb into the back of the boat by the driver. That makes it interesting during night sampling. The guys in the front think its funny, but when you see teeth and that front foot coming at you out of the dim light, it scares you know matter how used to it you are! Manatees also cause a threat as they can literally flip the boat if they are in shallow water. My first month on the job we were electrofishing on the St Johns near Titusville and in the front of the deck a huge swirl and the water dropped about a foot, before this 10-11 footer threw his head between the railing and onto the boat deck. Being from Missouri, that was first really scary then was pretty cool!
The term Monkey Rig is frequently used when describing illegal electrofishing. Those were specifically used for catfish and most were built from the old crank telephone generator. The reason it works so well on catfish is it is low amperage, medium volts, but low pulses per second, which catfish are very susceptible to. When I did my catfish research on the St Johns in the late 80’s and early 90’s we actually abandoned the modern day shocker and used an old telephone rig we built in some areas of the study, and it was amazing how many catfish were in any stretch of the river.
Below are a few photos of the inside and setup we use.
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| The action is not always fast paced, and sometimes it is a wait for the fish to float, or to even find them! |
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| You can see how crowded the boat can get even for the driver with all the equipment in the boat. |
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| Smaller boats are better for smaller water, but bigger boats are best for big waterbodies especially if bad weather or winds pop up. |
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| Clean, cool aerated water in the tank keeps all the fish in good shape while waiting to be measured, weighed and released. |
