Electrofishing: Monitoring Stream Health with Fish Surveys


Written by Sarah Becker and Christian Schluter

A little before 10:00 am on the morning of August 2nd, a group carrying nets, clad in fishing waders, and wearing backpacks reminiscent of the Ghostbusters franchise’s ‘Proton Packs’, met to hike to Cabin John Creek. This 11-person group of Montgomery Parks Department employees and volunteers were on their way to a 75 meter section of the river, specifically chosen for electrofishing. A modern method of fish sampling, electrofishing is a process by which large samples of fish can be efficiently captured, identified, weighed, and measured for stream health monitoring purposes.

We began the process by placing nets across both ends of the stream section, anchoring them in place with rocks and branches to ensure none of the fish escaped during collection. Downstream of the nets we organized ourselves into lines. In the front were five backpacked Montgomery Parks employees. Their battery powered electrofishing backpacks administer an electrical current to the water. This current elicits an involuntary reaction in the fish, causing those in the water to swim towards the source of the current where they can easily be scooped into nets. The rest of the group stood a few paces behind them, armed with nets and water filled buckets to catch any of the fish that slipped past.  

As we moved upstream, the backpacks generated a wall of electricity that briefly stunned the fish, making them easy to net. As the fish were scooped up and the nets were filled, they were exchanged for new nets from the back. We moved efficiently upstream, moving fish and eels from the electrified water to the oxygenated buckets. By the end of our first pass the buckets were full, and we moved back downstream to record the collection.

Two expert identifiers sat next to the fish buckets, removing fish to examine them before calling out an identification and releasing them downstream of the monitored section. As each fish was identified, a third person nearby recorded the species and kept a running tally of the counts. Once finished, the entire process was repeated again in a second pass to ensure all fish in our 75 meter section were accounted for.

As the fish were identified and counted, several of us headed back along the stream banks to conduct a ‘Herp search’ for reptiles and amphibians. We checked under logs, rocks, and other possible hiding places in search of frogs, snakes, salamanders, and other such critters. Nothing turned up after two passes, although later a Northern water snake was spotted swimming in the river. It was followed downstream until it reached the obstructive netting, at which point participants swooped in with nets and captured it for brief study.

Similarly to ANS’s Water Quality Monitoring Program, all the data collected from this event and from similar events is being used to monitor the water quality of local streams and rivers. The Montgomery County Department of Environmental Protection compiles fish sampling data and other indicative information to generate stream health scores, helping us all to see which areas are in need of the most attention. The Montgomery Parks Department is also working on a web based application that is currently under development, but will display baseline stream conditions to the public. Understanding this information makes it easier for organizations to make informed decisions about stream restorations, and other stewardship decisions.

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