DOW’s shocking way to count fish
Post Independent Staff
GLENWOOD SPRINGS – A group of fishermen bagged a record day on the Roaring Fork River Tuesday.
Three boats and 13 people pulled in just about every fish in the river. They caught literally hundreds at a time.
The success didn’t come from a new fly or a secret fishing hole. In fact the group didn’t even use a rod. They were “electro-fishing.”
A Colorado Division of Wildlife crew used electrical current to net fish for fish population estimates on the Roaring Fork, said Alan Czenkusch, an aquatic biologist for DOW.
The fishing happened Tuesday and Wednesday on the Roaring Fork between Carbondale and Glenwood Springs, said Czenkusch.
On Tuesday, the fish were caught, measured, weighed, counted and got a hole punched in their tail before being released. Wednesday the fish were caught again, measured, recorded and released again.
By recording the number of fish caught the second day that already had a hole punched in their tail, researchers can figure about how many fish are in the river, said Czenkusch.
“It’s algebra,” he said.
The department also gets an idea of how many browns, rainbows, and whitefish are in the river, said Czenkusch.
Researchers also get to look at a large number of fish, said Czenkusch, which helps them get an idea of the average condition of each species.
“It’s a really good fishery,” said Bill Elmblad, a DOW fisheries biologist from Grand Junction.
The Roaring Fork is a state-designated Gold Medal River. Czenkusch said for a river to gain and maintain gold medal status, it must have 60 pounds of trout per surface acre and at least a dozen fish per mile that top 14 inches in length.
Tuesday’s operation involved three boats, with three people handling each boat.
Each boat had a gasoline-powered electrical generator and negatively charged electric cables with loops at the ends dangling off either side of the bow.
One person controlled the movement of the boat, generally by walking in the river behind it. The second person threw a broom-shaped, positively charged electrode into the river and dragged it back to the boat. The third person netted the fish and put them in a holding tank on the boat.
“The fish actually swim toward the positive electrode,” said DOW fish biologist Dan Kowalski.
Though most fish make it through the shock and counting process, some don’t.
“We try to set the voltage conservatively,” said Kowalski, and “get the fish out of the (electrical) current as soon as possible.”
“With any operation you’re going to lose a small percentage of the population,” said Larry Green, who is retired from the DOW but helped with the population count Wednesday.
DOW employees enjoyed the fish counting operation.
“I get to go along and play,” said Elmblad. “It’s fun.
With three people on a boat in a moving river and hundreds of squirming fish, the operation can be exciting.
“It can be chaotic at times, but a lot of fun,” said Kowalski.
Contact Ryan Graff: 945-8515, ext. 535
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