What’s in Your Lake? Electrofishing Can Provide a Shocking Answer.
By: Steve Bardin – Justin Bryan
First let me say that managing fish in a private lake is actually really simple. Just like any wildlife species, to be successful managing fish you need abundant forage, diverse habitat, genetics that promote desired traits, and reduced competition for food and space. The reason lake owners perceive managing fish to be difficult is because you cannot see the fish underwater. Therefore, as the fish reproduce and consume forage it is impossible to keep up with the true number of fish in the population. Professional fisheries biologist use electrofishing surveys to try to gain knowledge of what is actually below the surface. We use electrofishing to determine the condition of the predatory fish, the abundance of forage, the presence of “trash fish” and gain information on what improvements can be made to the fishery. The data we collect during the survey determines what fish species will improve the forage base, where to add habitat, how many fish feeders are needed, and where bottom diffusion aeration should be placed.
These surveys are usually done in either the spring or fall, somewhere between water temperatures 65°F and 80°F. This is because, at these temperatures, all sizes and species of fish are active in the shallow water. Over the years I have found that the saying “90% of the fish are in 10% of the lake” is completely true, especially for small water bodies. Unfortunately, electrofishing does not capture every fish in the lake, instead we usually acquire a small percentage and use that data to make decisions with.
How electrofishing works is fairly complicated. First power is created by a boat mounted generator. That power is sent to the electrofisher control box which turns the electricity into a useable voltage, amperage, and frequency. The output is sent to electrodes which extend in front of the boat and into the water. This is where it gets complicated. The electricity uses the water as a conductor to travel back to the metal haul of the boat. The conductivity of the water dictates how quickly the electricity can move back to the boat. If the right conductivity is matched to the right voltage and amperage fish between the electrodes and the boat will be temporally stunned. If the conductivity is too high the electricity will simply go around the fish and back to the boat taking the easiest path. If the conductivity is to low electricity won’t make it back to the boat to close the circuit. What complicates things a little bit more is that all fish have different densities based on their muscle tissue and scale type; therefore, there are certain fish that don’t stun as easily. Other things to worry about are water color and clarity, if it’s too easy for the fish to see the boat they swim off, and if it’s too turbid we cannot see the stunned fish.
Typically, electrofishing surveys are conducted in managed lakes at least once per year. These surveys are designed to cull undesired fish and check the success and failure of management strategies. Another perfect time to conduct an electrofishing survey is before or immediately after the purchase of a new lake. Over the years I have conducted 100s of pre-purchase electrofishing surveys, most of the time the results are positive however, every once in a while I find trophy largemouth bass lakes that are lacking trophy sized fish or are even lacking fish completely. If you want to gain insight into what is actually in your fishery or one you plan to purchase, contact a professional and gain the knowledge electrofishing can provide.