Tracking Mississippi River Walleyes
Summary: Prowling the edge of the wing dam, we went just a few minutes without success. Then, one appeared. A quick dip in the water and Caleb Schnitzler pulled nearly five-pound walleye on board. This one would be going right back in the water shortly; along with the three bigger ones that followed on the Mississippi River, upstream from Sabula, in Jackson County.
First, though, each had a short date on the on-board operating table. After each thick, bronze fish was anesthetized, measured and weighed; a careful belly incision was made. As Schnitzler held it steady, Department of Natural Resources fisheries technician Dennis Weiss slid a slender radio transmitter into place. Another smaller puncture, an inch or so behind the incision, allowed an 18-inch antenna to trail behind the fish. About the size of a 20-gauge shotgun shell, the transmitter disappeared as Weiss quickly tied three sutures to close the wound. After a few minutes, each walleye ‘came to’ and was slid back into the water.
From here, they’re marked fish-electronically speaking. For the next two to three years, research workers at the DNR’s Bellevue fisheries station will track the lunkers; across winter ice and through summer heat. “We want to find out what kind of habitat these fish utilize in the winter,” explained Weiss. “It’s normally deep water areas, behind certain wing dams. We want to protect those areas.”
The wide Mississippi might spread for many miles, but quality habitat is hard to come by in a harsh winter. Perhaps the bigger concern, though, comes as ice breaks up in April and walleyes move into shallows. “We’ve documented two main spawning grounds in this pool. We want to make sure the fish continue to spawn in those sites, to protect them,” said Weiss. Each half-mile stretch lies on an outside bend, letting the current scour away sediment. Left behind is the sand/gravel substrate and strong water flow walleyes need for spawning.
This radio tracking has been underway since the early 1980s. For the last 10 years or so, crews have planted transmitters in 15 to 20 more big walleyes. Over the years, the equipment has become more sophisticated. The transmitters are smaller but stronger. The equipment-such as hovercraft in the winter-is more adaptable to the river. However, the aim is the same. Learn more about walleyes, and the environs they require. “All the walleyes on the Mississippi River are naturally reproducing walleyes. We’re not stocking them from our hatcheries,” noted Weiss. “We have to ensure we continue to have good numbers of brood fish.”
With the mix of fish, wildlife and human involvement, it’s critical that those high priority areas are identified. Barge fleeting areas, a river terminal or some other development are better suited away from the fragile spawning areas, for instance. Reduced bag limits and a slot limit on walleyes place some of the burden on anglers, too. “We’re going to have better walleye fishing with good spawning success with these fish,” said Weiss. “They need specific spawning areas and specific wintering areas.”
Wing Dam Walleyes
Though fisheries workers Dennis Weiss and Caleb Schnitzler were turning their ‘catch’ loose after the onboard transmitter work, it’s worth it to notice where those big ones came from. While a dozen boats bobbed just below the tailwaters in late fall-and with those tailwaters off limits beginning December 1 on several pools-the DNR crew headed downstream for the big walleyes they needed to carry the transmitters for two or three years.
With a south wind blowing upstream, Weiss guided the boat along the telltale calm, then ripple which indicated a wing dam just below. “We find a lot of big ones on the upstream side of the wing dam,” hinted Weiss. “Below the dam its too deep for our electroshocking. On the top, though, that water gets ’squeezed’ in effect. There might be eight feet of water pushing downstream, but that wingdam only lets about three feet of water over…and with it, the gizzard shad and minnows walleyes are after.”
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