Posted: 10/12/04
Electrofishing turns up plenty of trout on Winnebago Creek
 Bill Thorn, a DNR Fisheries biologist, writes down information about cover for trout and the numbers of fish found on a pool on Winnebago Creek last week. Next to him is co-worker Doug Determan. It was an enjoyable day, Thorn said. ìI think thatís what most of us enjoy, thatís the fun part.î |
By David Heiller
Argus News Editor
Talk about catch and release on Winnebago Creek!
Six ìfishermenî did that by the hundreds on October 7.
They werenít fly fishing, and they didnít have nightcrawlers either.
Winnebago Creek has been the subject of some controversy this year because the Minnesota Department of Natural Resources has proposed making it catch and release only, with no natural bait allowed. Local opposition to that has been fierce. A decision is later expected this fall.
But there were no politics or or controversies in sight at the creek on a cool, damp day last week.
These DNR workers were electrofishing.
They waded up about 20 pools in a mile-long stretch of the creek in Winnebago Township, north of the old Ray Schutz farm. In their hands they held long rods tipped with circular electrical probes. The rods were plugged into batteries in boats that they pulled behind them.
As the men walked and swung the probes through the water in front of them, the trout went a little silly. Some of them jumped out of the water, or did little dances on the surface. Some spun in circles. All were drawn to the electricity in the probes.
When a big trout came near, someone would scoop it up with a net that he held in his other hand. Most of these fish went right back into the water. But the biggest ones, those approaching 15 inches, were either tossed into a washtub in the boat, or measured on a board on the boat.
Those 15-inchers were what these men were after. As DNR worker Steve Klotz told me before they hit the water, the goal was to try to develop a predictive model to determine the number of large trout. They were measuring habitat too.
(See the sidebar that is with this story for more on the research that the electrofishing is producing.)
I followed the men up the stream for an hour last Thursday.
First, biologist Doug Determan explained how the electrofishing works and draws fish to the anodes in the water without hurting them.
They were using a direct current (DC) system, which Determan said is better than alternating current in clear streams like Winnebago.
ìItís easier on the fish too,î Eric Merten added.
I asked what the mortality of electrofishing was.
ìI would say one percent or less,î Determan answered.
ìWeíre going to see lots of fish,î Bill Thorn said, unable to hide his excitement. He had just walked along the creek, and had seen many trout feeding.
ìSometimes on a degraded stream, itís not as clear as you;d like,î Thorn said.
Winnebago Creek doesnít look too degraded to me, and I said something to that effect.
Merten explained that degrading came from logging and grazing that happened in the past, as far back as 150 years.
ìMassive erosion pretty much wiped out all the brook trout that were here at the time,î he said.
A good day for the project
Our conversation ebbed and flowed like good fishing conversation often does.
The weather was right for this outing, Jim Melander said: nice and cool, which is good for keeping the fish that go in the tubs in good shape.
ìThis DC on browns, I canít even remember the last fish we killed,î Thorn said. Then he recalled one that died. It had been wounded by a kingfisher. ìThat opened him up to a real whammy.î
Most of the trout in Winnebago Creek are brown trout. There are some rainbow too.
Brook trout numbers are very low because the flow of the stream is down.
Why is that? ìNatural,î Thorn replied to my question.
Winnebago Creek is spring fed, Determan elaborated, and those springs come from the aquifer. It can take a year for rain to infiltrate the aquifer to fill up the base flow of the creek. So the dry spell that occurred last year might not show up for a year.
The creek was up now due to midsummer rains, Determan added.
That was enough small talk. The men were ready to go. ìWhen weíre on, you donít want to put your hand in the water,î Determan said to me with a smile, as if he had seen someone (a reporter?) do that a time or two.
I followed along the bank, took pictures, and watched the men at work. They walked steadily, sometime in water higher than their waists, swinging their probes like a blind man with a cane, scooping out fish, pulling the short boats over riffles.
It wasnít exactly easy work, but you could tell by the looks on their faces and their brief sentences describing this fish and that minnow that they were enjoying it.
They came to a barbed wire fence at one point, and took turns ducking under it. Melander asked Thorn if he wanted a break from pulling his boat.
Thorn, the oldest man in the bunch at age 59, said he liked to pull it. ìIíll let you young and nimble guys chase the trout.î
Most of our talking ended after that. The men would tell the kind of fish they caught, or the size if it was close to a 15 incher. Most fell short of that, with lots in the 12-13 inch range.
I left the men to continue their shocking job, feeling much the wiser, and glad that they were gathering information on Winnebago Creek.
Sidebar:
Habitat plays key role in size of trout in Winnebago
There arenít a lot of large trout in Winnebago Creek, and thatís because it lacks different types of habitat.
In a nutshell, thatís what Minnesota Department of Natural Resources workers have determined over two sessions of electrofishing on the creek.
In the latter one, which was done last week, six DNR workers found only six trout longer than 15 inches in a mile-long strech of the creek in section 16 of Winnebago Township.
Six large trout per mile is a little less than average, DNR Fisheries reseach biologist Bill Thorn said on October 8, a day after wading up the creek. But it didnít surprise him.
Thorn is leading a research project that is trying to determine the summer habitat of large brown trout (longer than 15 inchees). He said that pools (areas between riffles) in creeks need five kinds of habitat to produce big trout: water deeper than two feet, stream rocks, rip-rap, undercut banks, and wood or brush jams.
ìMost of the pools in Winnebago only had two or three kinds of cover,î Thorn said.
When a brown trout gets bigger than 15 inches, it has to move or die, Thorn said. ìIf they move, they expose themselves to mortality from birdsî Thatís where those differnt kinds of cover come into play.
Great blue herons and kingfishers are the two main fish predators. Mink take some too.
In partiular, there is a lack of brush jams and in-stream rocks in Winnebago because of the size of the stream and its location in an open corridor, Thorn said.
Overhanging grass in a number of pools serves the same function as overhanging banks.
The stream is a fast-growth area for brown trout, and itís full of fish in the 10-14 inch range. A good abundance of forage fish like sculpin, suckers, and shiners are giving quick growth to trout, Thorn said.
Thorn sampled 20 streams last year, and looked at 40 variables such as in-stream habitat, pool areas, size of stream, the forage species, and the total abundance of trout.
He and his fellow scientists analyzed the data, and found that the cover in pools and the streamís discharge or flow are the two most important factors.
He re-visited those streams this year, each of which contain 12-15 pools, to try to validate his findings. ìItís correlating fairly decently,î he said.
His final report will be written this winter. It probably wonít have any impact on the fishing regulation proposal for Winnebago Creek. The creek has been proposed as a catch-and-release stream, using artificial bait only. Local residents have generally been against that idea.
ìPersonally it kind of demonstrates to me that itís habitat that is limiting large trout abundance,î Thorn reiterated.
Most of fisheries co-workers think that habitat is more crucial than angling in determine whether streams grow large trout, he added. Thorn called Winnebago Creek a beautiful and classic spring-fed stream, similar to those found in Pennsylvaina.
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