Electrofishing 101

Measuring fish during a fish removal (The Watershed Company).

Summer and early fall are one of the busiest times for fishing at The Watershed Company –electrofishing, that is.

Our fisheries biologists use this valuable tool to capture fish for study and research throughout the year.  But during the summer construction season, The Watershed Company helps contractors meet their project permit requirements by using a device that temporarily stuns fish for easy removal fish from construction areas so that they can be safely relocated for their own protection and preservation.


Why and when are fish removed?

Biologists removing fish by electrofishing in Washington for a construction project (The Watershed Company).

July through September is the often-hectic “fish window,” usually the only time of year when in-stream work is allowed by permitting agencies such as the Washington Department of Fish and Wildlife. Typical in-water construction projects include stream realignment, habitat improvements such as log placement, and culvert work. Often these projects accompany road widening or utility improvements. 

Stream sections where the work occurs need to be dewatered. So if fish aren’t safely rescued, they’re toast!

Capture typically requires a combination of netting and electrofishing, although sometimes some fish may by herded out of the in-water work areas.  Since electrofishing can be somewhat risky for fish, even when done with care and expertise, seine and dip nets are used first to remove as many as possible.


How does electrofishing work?

Electrofishing, Fish Exclusion, Fish Removal, Construction, The Watershed Ccompany, Seattle, Washington

Electrofishing momentarily stuns fish with a specialized electric shock delivered by a fisheries biologist or technician wearing a backpack “Ghostbusters-style” apparatus.  Basically, they’ve been tased.

The electric current is delivered to the stream by two opposing electrodes placed in the water several feet apart. The current can be widely adjusted in both strength (voltage) and form (pulse width and frequency), taking channel dimensions, the sensitivity of the fish, and the water’s conductivity into account. A safe and conservative approach is to start with a low current level and incrementally increase the strength until fish are adequately stunned – as opposed to just zipping out of the way when they feel a tickle.

Stunned fish are carefully scooped up with a dip net and transferred in buckets for release along unaffected stream sections. Several passes are usually made through the work area with both nets and the electrofisher prior to and during the dewatering process

Fish removal is often done with a crew of two, a qualified fisheries biologist and technician, but three may be needed if a lot of fish are present or to meet permit requirements. The more notice, the better, for project planning. But since we understand these jobs are seasonal and subject to difficult scheduling, we do our best to make them a priority.  Besides, fishing jobs are fun, fast-paced, and exciting.

Have fish at your project site?

First, make sure you have a plan. Then, give us a call and let us know about your project.