SUMMER RIVER WALLEYES
August 22, 2012
As spring evolves into summer, river walleyes typically disperse downstream and break up into small groups, setting up temporary residences near current-breaking objects or structures. Once water levels drop low enough, flooded shoreline cover becomes too shallow to attract fish. Now walleyes have no choice but to move toward the center of the river or to holes formed at bends. Current becomes moderate, but it remains a primary moving force in the lives of gamefish and baitfish — something to be dealt with every moment of every day. As water levels drop, then, current-deflecting structures projecting into the river become prime summer walleye locations.
In adult or mature rivers, long shallow runs typically become devoid of walleyes because fish concentrate near deeper holes. Thus even small rivers with weak walleye populations may offer fair summer concentrations of fish.
Aggressive walleyes tend to lie near distinctive current breaks like rock points or along the lips of holes, rather than in basins, which appear to be used chiefly as resting or cold front locations. Look for visual current seams, eddies, or other distinctive interruptions in flows. Without the threat of freezing, currrent-breaking structures that drop into as little as 4 — 5 feet of water may hold plenty of walleyes in summer.
On larger middle-aged rivers, even straight stretches may be deep enough to hold walleyes in summer, provided that distinctive current breaks are present. The basins of deep holes near river bends may not attract many fish until fall. Natural rock points and wing dams become primary summer walleye locations almost everywhere they occur.
Fishing a big river like the Mississippi during summer is a pleasure. The hordes of fishermen who descend on the river for the spring walleye run are long gone; like walleyes, spring also concentrates fishermen. During summer, fishing pressure becomes lighter and more spread out. You'll catch plenty of walleyes and still have time to pull off the river at noon for a cup of coffee and a sandwich, and you'll be able to find a cozy restaurant to enjoy a traditional riverside fish fry in the evening, too.
During 1982 and 1983, Iowa Department of Natural Resources biologist John Pitlo and co-workers radio tagged and followed walleyes in Pool 13 of the Mississippi River. Their conclusions, coupled with our fishing experience on many large rivers during summer (and fall), provide a clear picture of where walleyes are, based on available habitat and water conditions.
Most larger river pools contain a tailwater area, a main channel, main channel border areas, side channels, river lakes, and ponds. Pitlo compared the time that radio-tagged walleyes spent in specific habitats to the amount of each habitat type in Pool 13. Seventy-five percent of Pitlo's walleye observations occurred in about 25% of the available habitat.
"To be more specific," Pitlo said, "wing dam habitat makes up only about 5% of the habitat available in Pool 13, but it accounted for 32% of our observations. Flowing side channels make up about 15% of the habitat and accounted for 23% of our observations, and main channel border areas make up about 5% of the habitat and accounted for 20% of our observations."
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In essence, wing and closing dam structures are the principal walleye areas under normal pool (water level) conditions during summer and fall. Main channel border habitat is most important when the water level is low in winter.
As the amount of water discharged from Lock and Dam 12 increased, walleyes' use of wing dams decreased. Under high water conditions, in other words, walleyes vacate wing dams for side channel habitat, in which they are protected from heavy current. When the water drops, they move back to wing dams.
The Best Wing And Closing Dams
Some habitat areas, in this case certain wing and closing dams, are better fish attractors. The two most important physical characteristics affecting walleyes' use of wing and closing dams are the depth over each structure and the location of the structure in relation to the river's meandering channel.
Water depth is greater around structures located on outside river bends and less on inside bends; so is the current velocity over the top of those structures. Some of the volume is directed toward the main channel, while the remaining volume increases in velocity in order to pass through the restriction. Current velocity almost doubles over the top of the structure compared to velocities upstream and downstream. Higher current velocity increases scouring action and results in deeper scour holes below wing and closing dams, especially near structures located on outside river bends.
The quality and diversity of habitat appear to be enhanced by dams with shallow water depth over the top and deep scour holes below them. Many bait- and gamefish species gather around structures that possess those characteristics. Current velocity decreases with increase in depth, so deeper scour holes make better resting spots. This, plus the diversity of fish life, probably makes wing dams with these traits better areas for walleyes.
Feeding Versus Resting Walleyes
The deep scour holes behind wing and closing dams make good resting spots for walleyes, but fish don't usually feed there. During summer and fall, feeding walleyes almost always position themselves at the base, just up the face, or on top of wing or closing dams.
Wing and closing dams are best located by (1) consulting a map of a river pool, (2) looking for marker cans that occasionally mark main channel ends of dams, or (3) watching for telltale signs of surface disturbance caused by water being forced over the top of dams.
Wind blowing against current sets up distinct wave lines that mark the tops of dams. Position your boat from 50 to 100 feet upcurrent from such wave lines, stay there, and you're in proper position.
If wind is blowing with current, you need to create your own wave line by motoring along the backside of the dam with your boat. It's amazing, but one run usually sets up a distinct line that can last for 10 minutes.