Written by Dylan Kwak, Wildlife and Fisheries Scientist
Unlike management of deer or bird populations, which are visually observed, collecting fisheries data requires methods designed specifically for aquatic habitats. Fisheries Biologists use a variety of sampling techniques to overcome the difficulty associated with properly assessing fish populations. Common sampling tools include gill nets, traps, angling and electrofishing. Electrofishing is one of the most common and successful techniques for sampling fish in shallow water.
Electrofishing offers many benefits that other sampling techniques do not. Gill nets and traps, for example, reduce the slime coat of fish, making fish more susceptible to parasites and diseases. Due to the passive nature of other sampling techniques, fish commonly trapped in the nets do not survive. Furthermore, angling and nets tends to target specific size and/or species of fish. Electrofishing, on the other hand, can capture all species of fish that are accessible in the water.
Electrofishing is a management tool that safely stuns fish using a specially-designed boat. Fish are temporarily stunned with either a pulsed direct or alternating current produced by a generator. The electricity is passed through anodes that suspend from a boom at the bow (front) of the boat. Fish within a close radius of the boat are affected. In a freshwater environment, electrofishing works well due to fish having a higher salt concentration than the surrounding water. The salt concentration conducts the current at a higher rate than the surrounding environment, leading to a successful sample. Once stunned, the fish can be retrieved by a fisheries biologist on the boat’s bow and placed in a live well for observation and recovery.
To properly assess a fishery, biologists require data on species composition, weight and length, among other characteristics. For more intensive management, a fisheries biologist may also identify genetics, age fish, determine sex, and tag fish with a unique identifier. The data collected provides a snapshot into the fishery at the time of the survey. Biologists analyze the data to develop a report addressing the species presence in the lake, the size structure of the fish population, the balance of prey-to- predator ratios, and forage availability for predatory fish. Based on the information compiled in the fisheries report, a biologist can make recommendations and customize a fisheries management plan that considers the unique needs of the waterbody and goals of the property owner.
Fisheries biologists rely heavily on data to build a fisheries management plan. Although there is more than one technique to observe fish populations, electrofishing allows biologists to safely obtain the required information and make science-supported recommendations. When planning for the future of your fishery, it's recommended to work with a professional fisheries biologist and start with an electrofishing survey.
DISCLAIMER: When an electrofishing survey is employed, for the safety of the fish and the crew it is imperative that a skilled professional operator is in command of the vessel and the electrical systems. Electrofishing can be dangerous for people and fish alike when carried out by untrained personnel. Since every lake and pond is unique, the precise settings and appropriate outputs will vary and must be accounted for by the operator. While no sampling method is without stress for fish, when properly conducted by trained biologists, electrofishing is one of the most effective and efficient ways to collect fish and will result in minimal stress for the fish.
Contact the experts at 888-480-LAKE (5253) for all of your lake, pond and fisheries management needs.
Dylan Kwak is a wildlife and fisheries biologist at SOLitude. He is responsible for the ecologically minded management of aquatic vegetation in lakes, ponds and fisheries, and has a special interest in the identification of aquatic plant species. Dylan also works with clients to develop effective, long-term fisheries management plans using fisheries data analysis and sampling.