MONTEVIDEO -- For 30 years the Minnesota Department of Natural Resources has been electro-fishing the Minnesota River to coax out the secrets of the fish in its murky waters, and the intrigue only gets better.
"You never know what you are going to see,'' said Brad Koenen, a Clara City native and fisheries technician with the DNR in Hutchinson. He described the often-times surprising findings to a room full of people as a guest of Clean Up the River Environment on Jan. 27 in Montevideo.
Standing in the bow of the boat as electric lines dangle in the water, Koenen and co-workers use nets to scoop up, identify, weigh and measure the fish that bubble up to the surface, all of them stunned briefly by the electrical field.
He's netted snake-like American eels as far upstream as Granite Falls. They had traveled for thousands of miles before he could jolt them: The eels spawn in the Sargasso Sea in the Atlantic Ocean.
He's shocked other stretches of river only to see prehistoric, but native fish like shovelnose sturgeon and short-nosed gar float to the surface.
And, he's dropped the electrically-charged cables into deep holes 20 or more feet down, and watched as tub-sized flathead and channel catfish emerge into view.
Redhorse suckers will jump from the water to escape the current like missiles being launched, while fingernail sized, adult sunfish will flutter upward in the current like leaves in the wind.
Overall, there's the possibility of seeing any of 90 different species of fish when electro-fishing the Minnesota River, said Koenen, who has been at this since 1988.
The good news is that this has held true all of these years. The diversity of fish in the river may even be growing. Electro-fishing, angler reports and other work shows that more paddlefish and blue suckers are being found, two species that had apparently been absent or nearly so for some time.
Koenen said more research is needed to know if their increasing presence is due to improvements in water quality, or if higher, average flow levels experienced in the last decade are the bigger factor.
The electro-fishing research has shown that the river is a very homogenous resource, said Koenen. The diversity of fish is a fact all the way from top to bottom, a length of some 330 miles.
This is also a very productive waterway. Electro-fishing can shock more fish per hour than sometimes can be netted; up to 873 fish were counted in one hour in one case. "Unprecedented,'' said Koenen of the abundance of fish in the Minnesota River.
By sheer mass and size, carp are the dominant species found. Native fish such as suckers and sheepshead (freshwater drum) are well represented. Popular game species including sauger and walleye, flathead and channel catfish, white bass, northern pike, smallmouth bass, and crappies show up as well.
The river is and has long been home to a sizeable population of shovelnose sturgeon, said Koenen. Kenny Peterson, who lives below the Minnesota Falls dam south of Granite Falls, has also collected evidence to document the existence of lake sturgeon in the river, although they have not been found through electro-fishing, according to Koenen.
The river is very rich in minnows and forage fish, a factor that may support the worth of stocking more game fish, he pointed out.
The river's flathead catfish attracts anglers from places as far away as Texas and Nebraska, and for good reason, according to Koenen. He's pulled trot lines holding some of the monsters. A 51-pounder caught near Fairfax in Renville County is the largest. Some of these big guys probably are 30 years or older, based on age-sampling.
For years, it was assumed that flathead catfish spawned in the Mississippi River and made their way upstream in the Minnesota.
Electro-fishing has shown that the Minnesota River is a flathead catfish nursery all its own, with juvenile fish being found from below the Minnesota Falls dam to the confluence.
From 1990-2000, workers tagged some 4,000 flathead catfish, half of them larger than 12 inches in size. Anglers "recaptured'' 500 of the fish, a catch rate that is hard to beat, according to Koenen.
The Minnesota may not hold the 60-pound monsters that Southern fishermen can brag about, but Koenen said the distribution and abundance of catfish in the 10- to 40-pound range catfish puts the river in a class by itself. Devote a weekend to fishing flathead, and you have a very decent chance of tangling with a 40-pounder, he noted.
Electro-fishing and the aging of captured channel and flathead catfish revealed that the river holds a very mixed-age population of the two fish species. Unlike most waters where there are usually larger numbers of juvenile fish as compared to larger, older fish, the catfish population is well distributed by size and age in this river, he said.
Of course, you always have a very good chance of catching who-knows-what-else. "That's what I love about the Minnesota,'' said Koenen.
He's expecting to get more opportunities in the years ahead to see what's there. The DNR is planning to increase its electro-fishing researching to make it an annual activity on the river, he said.