During the summer and fall, Sheridan regional fisheries biologists conduct annual electrofishing surveys on several water bodies in the Sheridan area. This year, surveys have been or will be completed on the North Tongue, South Little Tongue and Little Tongue rivers, as well as Bull, Lick, Red Gulch, Wagon Box, Little, Big and Goose creeks and others.
Anglers are usually interested in this unique sampling technique when they see us in the field and often ask what we are doing, how the operation works and if the process injures fish or impacts their fishing.
Our boats are very specialized pieces of equipment. The front of the boat has a high railing to keep personnel safe when leaning over to net fish. A 5,000-watt generator in the boat is connected to the Variable Voltage Pulsator. The VVP alters the electricity from the generator into a direct current (DC) pulsed output. Several studies have shown that pulsed DC has the smallest negative effect on fish. The electricity enters the water at the front of the boat in front of where the netters stand. The electricity temporarily stuns the fish within about four feet around and under the boat. When stunned, they typically swim erratically or turn over. The netters then use 10-foot nets to quickly net the fish and put them in a livecar in the boat. Once the livecar has enough fish, we stop to measure and weigh each fish.
Electrofishing of smaller streams is done on foot, with biologists carrying backpacks with a battery or gas generator and holding a probe that conducts electric current into the water. Other personnel walk alongside with nets to collect the stunned fish. This technique is used on streams too small for boat access.
By keeping track of how many fish we catch each pass, which pass they are captured on and how many total fish we capture, we can generate population estimates to compare from one sampling event to another. These data show if the population is going up or down, what size the fish are and how heavy they are. These data are used to evaluate changes in stocking strategies or regulations. All the fish we sample are released back into the creek.
Any time fish are handled, whether it is by fishing or electrofishing, some fish die. However, based on our observations and the results of many studies, a very small proportion of the fish we handle later die. Without electrofishing, we would be unable to adequately assess the health of our fisheries.
If you are fishing close by when we are electrofishing, please stay clear until we shut the equipment off. Once off, we welcome you to come over to see all the fish we’ve caught.
Paul Mavrakis is the Sheridan Regional fish supervisor with the Wyoming Game and Fish Department.