Last Updated on August 11, 2020 by Kimberly Crawford
Electrofishing is a scientific survey method commonly used by fisheries biologists and pond owners glean insight into the freshwater fish population.
Some of the information you can gather through the use of electrofishing include age distribution of fish, growth rate, species composition, and whether invasive species are present.
For those that don’t understand electrofishing or want to learn more, use this guide as a starting point:
How does electrofishing work?
Electrofishing uses electricity to manipulate the movement of fish. It encourages them to swim towards the electric current using a submerged device that consists of a cathode and anode. The cathode is the electrode where oxidation occurs, and the cathode is the electrode where reduction occurs. (source)
This creates galvanotaxis in the fish—a biological process where cells or organisms are steered by an electrical field or current because of uncontrolled muscular convulsions.
When they swim toward the anode, they can be caught. If the technique is executed correctly, there is no harm done to fish and they are safely returned to their environment, typically within a two-minute timeframe.
Types of electrofishers
There are three primary types of electrofishers: backpack models, boat mounted models, and tote barge models.
Backpack electrofishers use battery or gas power to create an electrical current, utilizing a transformer to pulse before the current is delivered into the body of water. (source)
Tote barge models are similar to backpack electrofishers, with the main differentiation being that the generator resides on a floating barge, rather than a backpack.
These barges can also be left stationary in water, with long anodes and cathodes that allow users to sample wider ranges of water and fish species. With boat electrofishing, the boat itself acts as a cathode and anodes are mounted onto the bow. As fish swim towards the bow, they’re caught with a dip net.
How does electrofishing work?
As previously mentioned, the electrofishing process involves using anodes, which are positive electrodes, and cathodes, which are negative electrodes. This creates an electric current that, when submerged in water, creates an involuntary muscle response in fish that makes them swim towards the device.
Once they have approached the anode, they go into a state of narcosis, or unconsciousness, and begin to float belly up in this stupor for just a few seconds. This gives electrofishers the opportunity to quickly net them and place them into a holding tank, or live well, that contains the same water from the fish’s natural environment.
They’ll remain in the tank throughout the duration of the sampling period, and will remain here until they have been processed.
Different lakes and ponds have different water quality levels, and therefore vary in difficulty in terms of electrofishing use. For instance, some waters contain compounds that make it easier to conduct electricity, while others contain a high mineral content that makes it difficult to conduct electricity.
How does electrofishing affect fish?
In the majority of cases, electrofishing doesn’t harm the fish. After biologists have collected their sample scales, measured them, weighed them, identified the species, and collected any other data, they are returned to their natural environment.
Electrofishing is also a much safer sampling method compared to other types of sampling methods that could entangle, hurt, or kill fish during the process.
Furthermore, it also doesn’t affect fish eggs. Because of this, the Florida Fish and Wildlife Conservation Commission (FWC) uses electrofishing to collect data on breeding females at state hatcheries, as do many other fisheries, conservatories, and habitat management operations.
There are a few exceptions where fish might be kept, rather than returned to the lake. For instance, a particular fish, like a bass, might be kept if the biologist or researcher finds that overpopulation is prominent in the area and the fish might be used for further evaluation.
Or, they might be removed from lakes that don’t have enough fishing barometric pressure—the weight that presses down on fish, and every other living thing on the planet. Removing bass from lakes that don’t have enough fishing pressure can prevent crowding.
Electrofishing controversy
Because electrofishing is an unnatural way of securing fish, naturally there is some controversy regarding the practice. However, the biggest controversy revolves around the use of electrofishing or “pulse” fishing commercially, which is banned in many countries or capped at a quota.
Another issue with large scale or commercial electrofishing is that it hurts other types of marine life that aren’t targeted, and creates a negative chain reaction under the surface, ultimately damaging other sea animals. Some scientists say that the electric current can break the spines of fish, kill young fish, and reduce the hatching rate.
The current restrictions in place are designed to protect the environment, but the unfortunate fact is, some organizations or fishing businesses give the technique a bad name by defying those regulations.
For example, over the years, the electric pulse method has been used in protected marine areas.
In October 2019, an investigation from the Times found that standard fishermen were using this technique in Dogger Bank, an EU-designated special conservation area between Northern Europe and Britain.
Large vessels were used to capture a variety of fish in one of Europe’s largest marine protected areas. But it wasn’t just electrofishing on steroids that played a role—heavy beam trawling was also used to pull low-lying sea creatures like shrimp from sea beds.
Beam trawling is seen as a “cousin” to electrofishing. Though there are different types of trawling, the practice is relatively the same: a fishing net is lowered onto the seafloor and dragged along the seabed with the movement of the boat, collecting pelagic fish like anchovies and mackerel. Studies have shown that trawling can cause significant environmental damage.
Charles Clover, executive director of BLUE Marine Foundation, addressed the use of illegal electrofishing in Dogger Bank. He said in a statement, “There is nothing experimental about this fishery, it is a fully-fledged commercial operation and its environmental impacts while under-researched are potentially very harmful. The Chinese used the technology in the 1980s but abandoned it because of its impact on fish stocks and the environment.
Despite some pushback, proponents argue that it saves fuel and is therefore better for the water and environment, drastically reduces the amount of unwanted by-catch, and does less damage to the sea.
More importantly, the biggest difference between electrofishing open water and on lakes is intent and scale: fisheries biologists return the fish, whereas fishermen do not. And the scale and volume used by large fishing boats far exceeds that of a lake electrofishing boat or backpack.
But while electrofishing is more controversial among open waters and in mass, there is very little pushback in regards to electrofishing in small, freshwater ponds when it’s used for sampling purposes.
Freshwater research does not use heavy electrical currents, unlike some of the commercial boats that use massive equipment and electrical nets. No research indicates any long-term effects on fish populations.
Benefits of electrofishing
The biggest benefit of electrofishing is that it allows biologists to quickly collect samples, and these samples offer greater insight into a specific body of water. This information can then be used to create a better strategy for managing a fishery or understanding a particular body of water.
From here, biologists can learn about feeding, habitat management, and fertilization. For instance, based on the data collected, a fishery can create better harvesting restrictions, gain a better understanding of what needs to be done to improve water quality, and much more.
Electrofishing also allows biologists to inspect species for sores or parasites that could be impacting the fish population; without analyzing these fish firsthand, any compromises to the habitat could go on for long periods of time unnoticed.
Electrofishing also allows biologists to discover invasive species that might be harming the population, and those species can then be removed to better manage the lake. And lastly, biologists are able to check the stomachs of predators to determine what they are eating. These samples can also reveal how quickly species are growing.
All of the information obtained can be used as a baseline to determine whether new changes are having a positive effect on the fishing population. If these types of tests were not conducted, biologists wouldn’t have the sources necessary to understand how the fish population of a particular area is being affected.
Is electrofishing legal? Where is it banned?
Electrofishing is legal for accredited research centers, and is used by many government agencies. Many individuals start their own pond management companies and are contracted as third party businesses to collect relevant data.
It is illegal to use electrofishing for recreational use in many states such as Florida, because it can be considered a form of poaching.
However, even in states where it is illegal, there are exceptions for individuals electrofishing on their own lake or permitted by owners of a lake.
For example, if you owned a property that contained a lake, whether you use the property for business purposes (such as a golf course) or private purposes (such a property-side private lake), you would be able to use electrofishing legally.
On the same note, anyone engaging in electrofishing activity should be trained to do so; untrained individuals can injure themselves dealing with electricity in the water, even at low voltage. Therefore, you should always hire a professional electrofisher to do the work for you.
Understanding waveforms
Waveforms describe the shape of the electrical current used for electrofishing. Electric current refers to the movement of electrons, and waveforms refer to the way the movement of electrons through water is created. There are four types of waveforms for this use case: alternating current, direct current, pulsed direct current, and burst of pulses current.
Alternating currents are only available on boats and barge electrofishers because they require a generator. Direct current is made through the utilization of electric fish handling gloves, and although it has the lowest capture rate, it also has the lowest potential for injury.
Pulsed direct currents are the most popular waveforms; with this type of current, the direct current pulsed several times each second. Each pulse of electricity helps to stimulate the nerves and muscles of the fish, making them least likely to be able to control their own movements, which is how galvanotaxis is achieved. This type of waveform offers tremendous benefits compared to the others, when used correctly.
Burst of pulses current is the least popular, and is often only used to remove fish from bottom substrate—the material that rests at the bottom of the water and allows organisms to live, grow, and collect nourishment. This method is effective at collecting lamprey, a jawless fish that attaches to other fish, clawing through their scales in order to feed on their body fluids.
How much does electrofishing cost?
The cost of electrofishing varies depending on the type of electrofisher, length of time you need it, length of distance you want to travel, impoundments, and the type of services you want.
For instance, a standard boat might cost $1,500 for the day, plus the cost of personnel and expenses. Other services might charge by the acre, with additional costs per mile.
These boats are often equipped with everything you would need, including a live well, storage, workspace, and easy launching access. If you’re interested in learning more about your pond or lake, contact local electrofishing companies to learn more about their pricing points.
As you can see, electrofishing can offer ample benefits, and is ideal for a variety of research purposes. Whether you run a fishery or own and manage property with a lake, an electrofishing survey can reveal what’s happening beneath the surface.
Safe electrofishing can improve the health and longevity of a freshwater population. Always due your due diligence when searching for operators; make sure the team you hire is licensed and insured.
Furthermore, if you intend to purchase electrofishing equipment, do your due diligence on the provider to ensure the quality of the product meets your qualifications.
