Not too long ago I was working the Blue River tailwater downstream from the Dillon Dam and noticed a team of ten or so anglers coming down the stream in a line. Each was holding a long poled net and carried some sort of backpack. I didn’t want to bother them as they were obviously on a mission of some kind. I waited to ask my buddies at my local fly fishing s hop, Minturn Anglers in Denver.

Apparently I had encountered wade electrofishermen. Colorado Parks and Wildlife (CPW) is responsible for the management of fisheries in Colorado. One of their most important sources of information is the lake and stream survey. CPW monitors hundreds of lakes and streams every year, and shares that information with Colorado anglers.

This survey information helps fly fishermen and women know the numbers of trout in particular streams, their length and weight, and is used to identify streams as Gold Medal or Blue Ribbon. The data is also used to track trends in fish populations, and helps determine actions taken to manage stocking and regulations.

Electrofishing is an often-used method of taking samples of fish populations to determine what species are prevalent in a given stream, as well as their density and abundance. CPW uses three types of electrofishers, the backpack model that I saw being used on the Blue River, boat mounted models as well as shore mounted units. They all use either one or two electrodes that deliver electrical current into the water, used to stun the fish. Backpack units are battery or gas powered, with the positive electrode at the end of a long pole with a long cable trailing behind the operator. Boat electrofishing uses the boat as the negative electrode, with positive electrodes usually mounted in the front. In all systems, netted fish are quickly measured and assessed, then released back into the water. Electrofishing is not harmful to fish and they do not suffer ill effects.

Electrofishing is an important method of gathering information to improving efforts to manage and preserve the sport of fly fishing well into our future. The next time I see these CPW workers out on the water, I will certainly pay close attention to what they are doing.