Got Space Invaders? Here’s a Shocking Response

Jan 18, 2024

Adult fall Chinook salmon.

Along Oregon’s Coquille River, smallmouth bass are having an outsized impact on the beloved—and beleaguered—Chinook salmon. These nonnative fish prey on juvenile salmon and generally outcompete the Chinook for survival in a changing ecosystem. With a fraction of the historic population returning to the River to spawn, Chinook salmon have become a priority species for conservation.

In hopes of giving the native salmon a fighting chance, the South Slough Reserve has teamed up with the Oregon Department of Fish and Wildlife (ODFW), the Coquille Indian Tribe, and local volunteers in a unique approach to removing this invasive bass: electrofishing. 

Each electrofishing vessel has a generator that runs a charge along two adjustable booms and into the water. The electricity temporarily stuns nearby fish, allowing them to be caught with a net and placed into a holding tank on the boat.

ODFW biologist Morgan Davies (left) and Reserve intern Jack Waddington aboard the electrofishing boat.

“We had tagged a bunch of bass that are worth money for anglers if they catch them,” says Gary Vonderohe, biologist at ODFW. Tagged bass caught while electrofishing are tossed back; the untagged ones are donated to help feed animals at, for example, local wildlife centers.

In the last three years, the collaborative team has removed upwards of 14,000 smallmouth bass. Whether this will be enough to decrease the stress on salmon remains to be seen, and the Reserve and its partners are addressing other drivers of salmon decline in the area.

“As forested swamp habitats have shifted to grasslands, the decrease in trees and shade-bearing vegetation has led to warmer waters,” says Jenni Schmitt, monitoring coordinator at the Reserve. “This has warmed the Coquille to near-lethal temperatures during summer months. Salmon are especially vulnerable to temperature; they need cold water refuges and these are in decline.”

Wetland restoration improves habitat for salmon by helping to provide food and protection for juvenile salmon. In the adjacent Coos River basin, the Reserve and partners have restored complex tidal channels to wetlands, and Reserve volunteers help collect field science data, remove invasive weeds, and share science education with visiting students.

Second Saturday Steward Volunteers remove invasive plants in the Reserve’s Wasson Watershed.

Newly planted, native willow trees in Anderson Creek.

The Winchester Arm is a subwatershed in South Slough that has hosted many past wetland restoration projects. It will also host the upcoming Wasson restoration.

Beaver Dam Analog Workshop in Wasson (South Slough).

Jack Waddington (Youth Science intern) and right Ryan Scott-South Slough Wasson Monitoring Technician installing a benchmark.

Summer intern Annaliese Schrandt biomonitoring Wasson marsh.

Smallmouth bass to be donated to local animal centers.

Netted fish held in the center tank of the boat.

This article was written by Taylor Cockrell, South Slough Summer Communications Intern through Oregon Sea Grant. Taylor conducted the field research and wrote the story to share the many ways the Reserve partners with other organizations to achieve common environmental goals.

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