Electrofishing - The Complete Guide & Shocking Truth
Electrofishing is not legal in most states for recreational use, but is commonly used by various universities and government agencies for surveying fish populations and densities in freshwater lakes and streams. As long as the process is done properly, there is no permanent harm to the fish and they are back to their natural mobile state within two minutes of being captured.
How Does Electrofishing Work?
Electrofishing uses two submerged electrodes (an anode and a cathode) that direct high voltage from the anode to the cathode through the water. This technique affects the movement of fish that are nearby, causing them to swim towards the anode where they can be immediately captured or stunned and then netted with a dip net.
The literal methodology is pulsed direct current (DC) is transmitted, causing uncontrolled muscular convulsion (galvanotaxis) that causes the fish to swim towards the anode in a magnetic-like fashion. Two people minimum are required to be effective; one operates the anode and the other captures the stunned fish with a dip net.
Fish most commonly come into the shallow waters to feed at night, which is why electrofishing is most commonly done from a boat at night in the shallows where biologists can easily see the fish they are targeting.
Types of Electrofishing
There are three types of electrofishing - boat mounted, tote barge, and backpack electrofishing. The method scientists use varies depending on the accessibility of the water body. The most common method for lakes is a boat mounted electrofishing system, and the second most common a backpack system which is used in shallow streams.
Boat Mounted Electrofishing (Stunboats)
Typically a 14 to 22 ft aluminum boat with an outboard motor is used. Most electrofishing boats have a platform with railing at the front of the boat. This is a common setup we see in flounder gigging boats as well.
Boat mounted electrofishing systems are typically the most advantageous for covering a lot of water. They can also be used more easily at anytime - day or night.
Boat mounted electrofishing is most commonly done at night with electrofishing lighting. Fish come into the shallows to feed at night, making it much easier to see and capture them while electrofishing.
Boat Mounted Electrofishing Equipment:
- Anode Array
- Cathode Array
- Junction Boxes
- Foot Switches
- Extension Cables
- Electrofishing Boat Lights
Here's a photo of an electrofishing boat from Smith-Root:
Tote Barge Electrofishing
These are commonly used in flooded fields and marshes that aren't entirely boat accessible but don't have the dry land and shallow stream obstacles you might have when using a backpack electrofishing system.
Tote Barge Electrofishing Equipment:
- Tote Barge Hull
- 5 Gallon Buckets with Holding Bracket
- Electrofishing Shock System - including electrode pole, anode/cathode, and power supply.
- Fish Nets
- Electrofishing Tote Barge Lights
Here's a photo of the tote barge electrofisher by Smith-Root:
Backpack electrofishing systems are most commonly used in areas that are hard to access and navigate. These include wandering rivers and streams that have water levels that may fluctuate from a couple feet deep to bone dry in different areas.
Backpack Electrofishing Equipment:
- Electrofishing Shock System
- Backpack Adjustable Shoulder Harness
- Electrode Pole
- Electrode Ring
- Rat-tail Cathode
- 24V Battery & Battery Charger
- Fish Net
- Backpack Electrofishing Lights
Here's a photo of a backpack electrofishing system:
Does Electrofishing Harm Fish?
When electrofishing is performed properly, it does not cause lethal or lasting harm to fish. One might say it's comparable to being stuck with a needle at the doctor's office - it may sting a little in the short term but after a couple minutes everything's back to normal.
There's a lot that goes into a successful electrofishing trip - and if not executed properly it can result in accidents. There are many outside factors - the fish size and species composition are important to consider, as is the water conductivity. One of the first things biologists do prior to electrofishing is test the water conductivity.
The variations in species size and water conductivity dictates how the electrofishing equipment is used. The pulse rate on the direct current (DC) electrical fields are less on smaller species and greater on larger species but even that can change depending on water conductivity.
If the electrical fields aren't adjusted properly, it can result in not stunning the fish long enough to be trapped or on the flip side it can result in a fish kill. Like most jobs, electrofishing does require a decent amount of training.
Does Electrofishing work in Freshwater and Saltwater?
Electrofishing is less commonly performed in saltwater than in freshwater systems. The reason for this is because saltwater is extremely conductive and the electricity travels through the water rather than through the fish.
In theory, freshwater that has no electrolytes or impurities is not conductive. However, as we know, there are many electrolytes and impurities in freshwater and exponentially more in saltwater which make it super-conductive.
Freshwater has an electrical conductivity around 1,500-1,800 microsiemens per centimeter (uS/cm), while saltwater has an electrical conductivity of approximately 54,000-55,000 uS/cm.
Most current electrofishing boats, namely Smith-Root brand (one of the most common brands in the USA), can handle up to about one-quarter saltwater mixture with freshwater. There is a new electrofishing boat by Grassl Saline out of Germany, which can handle higher saltwater concentrations nearing 54,000-55,000 conductivity.
Water conductivity is the single-most important factor to consider prior to electrofishing.
Is Electrofishing Legal?
In most states, electrofishing is not legal for recreational use and is considered poaching. Electrofishing is most commonly used by universities and multiple government agencies for surveying water bodies to see the different species of fish, their size, and population densities.