Equipment Spotlight: Stream Shocker
What does the Department of Natural Resources use to sample a stream or wadeable river to assess fish populations? The answer is a barge or stream shocker.
What is a stream shocker you might ask? A stream shocker is a small, boat-like tub that can be pulled or dragged through the water to house the equipment necessary to shock and capture fish (with generators and electricity).
Aquatic systems are difficult to predict and sample with nets so the department must use other means. Fish move frequently, use habitats differently, and can generally remain undetected. Most people think they know a stream pretty thoroughly, but time and again, electrofishing surveys turn up surprising results.
Similar to stun guns used to temporarily debilitate people, electrofishing temporarily stuns fish to allow fisheries personnel to scoop them up with nets. Fish are then placed in holding tanks where they quickly recover before being evaluated and returned to the water.
Larger streams and rivers require electrofishing units mounted in large, flat bottom boats, whereas smaller streams and creeks require electrofishing units carried as backpacks.
Electrofishing is the most effective method to sample a stream. The electrical current pulls fish out of even the best hiding places such as logs and undercut banks. The DNR uses electrofishing surveys to estimate species abundance, determine growth, recruitment and health, and to remove unwanted species. Monitoring stream fish populations helps the DNR determine stocking rates, fish health and if adequate habitat is available prior to a stream restoration.
So how does the DNR acquire a stream shocker? A few years ago it was necessary for the DNR, Fisheries Division's Southern Lake Huron Management Unit to replace their old stream shocker. The task was completed by one of their own fisheries technicians.
This is no easy process; it takes time and lots of expertise with the use of fiberglass and resins. The boat needs to be buoyant, water-tight and light weight. Most of the access points the Southern Lake Huron Management Unit sample are not right along the road and are usually several hundred feet to the river's edge so the lighter the boat the better.
The equipment in the boat consists of three reels, probes, a generator, a control box, battery, safety switch and tub to hold fish for processing. The reel allows for sampling both left and right of the barge at one time. The probe is the equipment in the water that stuns the fish and is hooked up through an electrical cord. The generator is how the electricity is produced and the control box regulates the current evenly to each probe. There is an element of danger but DNR, Fisheries Division staff take extensive precautions and implement many safety measures - as well as engage in on-going training - to safely use this equipment. On a yearly basis this specific unit will sample anywhere from eight to 12 streams that will require the use of a stream shocker.
This - among other types of equipment - is very valuable for the DNR, Fisheries Division and is critical for completing stream surveys. Check out the summer edition of Reel in Michigan's Fisheries where we'll highlight another piece of equipment!