Electroshock fishing

Wednesday, October 19, 2011

By Patrick Dolan

Jackson Hole, Wyo.-Over the past couple weeks, Fisheries biologist Tracy Stephens and others with the Wyoming Game and Fish have been electrofishing sections of Flat Creek and the Snake River to collect data on fish species. Electrofishing uses an electric shock to safely immobilize fish so they can be studied. Electrofishing is an effective process for collecting data on fish. They use electric current to stun and pull fish in, like an underwater tractor beam.

A team of two float downstream in a raft with a generator that produces an AC current. A variable voltage pulsator converts the AC current to DC pulse, which they have found to be the least harmful for the fish. A combination of negatively charged cathodes off the sides and positively charged anodes near the front, stun the fish and pull them towards the anodes.

“They get shocked and their bodies react to that and they go towards the positive anodes,” Stephens said.

The biologists can easily net the fish and hold them in live tanks to be measured, weighed, and in some cases, tagged, before being released.

 The native cutthroat trout is the target population and the data will be used to develop fishing regulations to properly manage and protect the native species. Stephens said that over all, the cutthroat population is large and healthy.

“On Flat Creek through the South Park Feed Grounds, we counted about 400 fish per mile for Cutthroat bigger than five inches,” Stephens said. “We have seen good numbers and lots of healthy fish, which is encouraging.”

The study included a five and a half mile section of the Snake River north of Wilson Bridge and three sections on Flat Creek. On Flat Creek, they sampled a one-mile stretch on the National Elk Refuge, a section through Karns Meadow, and another three quarter mile section through South Park Feed Grounds. This is the first time South Park has been sampled in more than 20 years, according to Stephens.  
“On the Elk Refuge we found some cutthroat trout, some brown trout, brook trout, and cutbows,” Stephens said. Cutbows are a fertile hybrid of the native cutthroat trout and the non-native rainbow trout.

Stephens said they were all pleased with the numbers of fish counted. “We expect high numbers for total populations once we can go through all the data.”

photo by PATRICK DOLAN
Regional Fisheries supervisor Rob Gipson steadies the raft as Fisheries technician Sarah Walker looks for stunned trout to net.


PERMALINK:
Electroshock fishing | Planet JH News Article: General Environment

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