June 21, 2024
By Dan Anderson
Meet Fred, a 45-pound flathead catfish living in a river somewhere in the U.S. Doesn’t matter which river, because Fred would behave roughly the same no matter where he lived. Researchers have discovered that while no two flatheads behave exactly alike, all of them follow the same basic rules—winter, spring, summer and fall—from the day they hatch til the day they die. Anglers who understand Fred’s day-to-day lifestyle, in conjunction with his seasonal cycles, have better chances of meeting him and his kin face to face.
In-Fisherman’s Calendar Periods describe Fred’s annual cycle well: Winter, Prespawn, Spawn, Postspawn, Summer, Fall, and back to Winter. The exact timing of the phases varies around the country. Prespawn, for example, may be in late March or April in Texas but not until May in Minnesota. Fred experiences those phases every year, and they affect where he is in a river system, how and where he feeds, as well as when and where he rests.
Radio telemetry allows researchers to track the movements of flatheads in various rivers around the country. In some cases, they’ve tracked individual fish hour-by-hour, day after day, for more than a year, providing insights into flathead behavior that can help anglers catch more and larger flatheads.
The Circle of Fred’s Life Starting with the Winter Period, tracking research shows flatheads tend to spend winters in wintering holes; deep areas in rivers with mild current flowing through submerged trees or areas of large rock or rubble. In northern states, as water temperatures fall below 50°F, flatheads from many miles of river may move toward specific wintering holes. In the South, movement toward wintering holes is less absolute, though flatheads tend to loosely congregate in or near deeper areas of rivers during winter months.
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“In the winter, flatheads we tracked were extremely sedentary,” said Sarah King, a research biologist who followed radio-tagged flatheads during a year-round, multi-year study on the Wabash River in eastern Illinois. “At times we sat (in boats) over tagged flatheads for so long without any signs of movement that we began to wonder if they’d died.”
As waters warm above 50°F and pass 60°F, flatheads move out of wintering areas and enter their Prespawn phase and begin a leisurely migration to spawning areas. Dr. Jason Vokoun tracked flatheads on several rivers in northern Missouri and noted that it wasn’t a mass migration like flocks of ducks.
“Each fish moved on its own schedule at its own pace,” he said. “Some swam back to the same exact river bend where they had spawned the previous year. It’s fascinating how, in the Grand River, many of the fish were able to move back from wintering holes in the Missouri River that are 50 or more miles from a specific spawning area, and pass dozens of cutbank river bends, until they reached a particular bend. Some of our tagged fish swam past spawning areas where other tagged fish were setting up to spawn. They swam to a specific spot and stopped when they got there.”
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Flatheads are cavity-spawners, depositing their eggs in holes commensurate to their body size. Logjams, beaver dens, and especially areas of large riprap may attract relatively large numbers of big fish. Areas that provide cavities and conditions suitable for spawning provide one of the few opportunities for anglers to catch dozens of flatheads from a relatively small area.
Postspawn, Fred and his fellow flatheads move to their summer areas. In the same way many flatheads return to the same spawning area each year, individual flatheads often show fidelity to specific places in specific rivers during the Summer Period. Summer areas may be only 100 feet from their spawning area, or may be dozens of miles up- or downstream. The loyalty some flatheads display toward specific summer areas in rivers provides veracity to stories told by veteran anglers about catching the same fish from the same logjam year after year.
“A surprising number of flatheads in a radio-tagging study we did returned to the same logjam every summer,” said Greg Gelwicks, fishery research biologist for the Iowa DNR. “Others were willing to settle into a new area if water depth, habitat, and food supply satisfied their needs.”
Once in their summer homes, flatheads tend to be homebodies. Vokoun and his coworkers tracked individual fish for 24-hour periods and were surprised to discover that many of the flatheads were stationary, in deep holes or buried in logjams, for an average of 23.1 hours per day. Those fish tended to make brief, decisive moves at night to shallow flats or drop-offs from sandbars, presumably to feed, before returning to the same spot in the same logjam.
“When they moved, they moved pretty much in a straight line,” Vokoun said. “Or as much of a straight line that a river channel with logjams and sandbars would allow. It’s like they knew exactly where they were going.
King’s research on the Wabash River showed flatheads usually conducted their summertime feeding forays around dusk or dawn. The old anglers’ adage that flatheads quit biting after midnight isn’t infallible, but researchers noted a flurry of feeding activity at dusk and shortly thereafter, a lull around midnight, then another increase just before dawn throughout the summer.
Flatheads sometimes alter their home ranges during summer. Dry summers with falling water levels in small rivers encourage flatheads to seek deeper water. Midsummer or early fall thunderstorms that temporarily raise river levels encourage movement as well. Fish that move (usually upstream) in response to rises in water level generally return to their summer areas when rivers fall, though a few fish sometimes find “better” habitat during their travels and stay in new home areas.
Cooling water in early fall encourages flathead movement and offers anglers new fishing opportunities. “Some of the best times to catch flatheads seem to be during transition times between seasons,” Gelwicks said. “It may be due to the fact that fish moving up- and downriver are exposed to more anglers’ baits, compared to those that are hunkered down in a hole or logjam.”
Once temperatures drop toward 40°F, fishing for flatheads in late fall can range from being “a waste of time” to “worth the trip.” There’s a logic to the discrepancies. In the North, the congregation of so many flatheads in a relatively small area in anticipation of winter can produce surprising action. On warm, sunny days, individual fish may range away from the “herd” to feed, and are susceptible to livebaits or bloody cutbaits fished along channel edges or drop-offs into holes.
Once water temperatures drop below 40°F, flatheads consolidate into wintering holes. Underwater videos have shown them crammed fin to fin with only faint movement of their gills. At around 35°F they become torpid, uninterested in moving or feeding. Southern flatheads don’t cluster as tightly they do up north, and often roam on warm, sunny days and feed over flats adjacent to deep-water areas they seek in midwinter. North or south, flatheads use the winter to reset their internal calendar in preparation for another year of Prespawn, Spawn, Summer, and Fall periods.
Exceptions to the “Rules” Given the seasonal mobility of flatheads, and with consideration for their sensitivity to changes in river level, sunlight, and other local, physical aspects of their world, there are multiple reasons why it can be tough to find flatheads on a given day. In no particular order, here are observations made by research biologists about flatheads they’ve studied that may help improve anglers’ understanding of the best places and times to catch flatheads:
“Flatheads you see in a particular stretch of river may only be there part of the year, or only while they’re moving through the area,” Vokoun said. “One spot may be great spawning habitat, or great summer habitat, and hold lots of fish during those times of year, but may not be as productive when the fish have moved into another phase of the year.” “Anglers who sit and wait for flatheads to come to their baits need to remember that many of the flatheads in our studies literally did not move for 23 hours a day,” Vokoun said. “That makes sitting and fishing one spot a low-percentage game, unless the spot is selected because it’s a travel path between a series of logjams where a number of flatheads rest and the sandbars and drop-offs where they go to feed.” Flatheads tend to follow channel edges, the bottom edge of a cutbank, or along some sort of bottom feature, when moving up- or downriver. They rarely motor down the center of a major channel, distant from any structure. Many large rivers have U-shaped channels that wind back and forth beneath their broader surface; flatheads moving up- or downstream tend to follow those submerged edges rather than cruise through open water. “Flatheads tend to hunker down in cover during daytime hours, most of the year,” said Dr. Robert Colombo, who directed the Wabash River study. “Especially in the warmer months of summer, they prefer to come out at night.” That means the best way to catch them during daytime is to drop a frisky livebait or bloody cutbait right down into their logjam lair, along the base of a cutbank, or between large boulders and chunks of concrete at the base of riprapped shorelines or bridge abutments. A veteran flathead hunter described the tactic as, “Dangle the bait on their nose or in front of them until they get mad and eat it just to stop it from annoying them.” It takes stout tackle and line to pull a big flathead from thick woodcover, but veteran anglers say the trick is to have tackle heavy enough to apply strong, steady pressure that persuades the fish to do the angler’s bidding. Frantic jerking and “horsing” isn’t as productive as steady, relentless pressure. In the Wabash River, a medium-to-large midwestern River with “good” woody habitat of fallen trees and logjams, researchers consistently found 20 to 25 flatheads per river mile. Large logjams could hold three to five flatheads of varying size, with the biggest fish claiming the “best” area in the pile. Smaller logjams or single rootballs often held only one flathead. King noted that submerged woody habitat was popular with many of their tagged fish on the Wabash River, but that, “if woody habitat wasn’t available they seemed to associate with deep channels or holes in the main channel. If there was a submerged tree rootball or something they could lay behind out of current, they seemed content to use mid-channel holes as a home area.” Gelwicks noted that when he and his team electrofished for flatheads, logjams were obvious targets, but areas of large riprap, especially slabs of broken concrete, held comparatively strong numbers of flatheads spring, summer, and fall. No matter how “good” a river looks for flatheads, flathead numbers trend lower upstream from a dam. Work by Jamison Wendel and Steven Kelsch in the Upper Midwest indicated that even lowhead dams can influence catfish populations. Smaller rivers with multiple dams may have limited flathead populations in their upper ranges because the fish are unable to move up- or downstream to appropriate wintering holes or spawning areas. All the researchers interviewed noted a trend where the biggest flatheads in a system took possession of the “best” habitat. In a large logjam holding three or more flatheads, each would have its own area within the logjam, with the biggest fish laying claim to the area with optimum current, shelter, and “catfish comfort.” “There may be multiple flatheads in a big logjam, but they don’t share specific spots,” Vokoun said. “They were apparently aware of each other’s presence, and if one vacated a prime spot, another one often moved into that spot fairly quickly.” He noted that if a big flathead is removed from a particular habitat, the “pecking order’ seems to reshuffle among remaining fish. “I don’t think you can “fish out” a logjam or hole,” Colombo said, “because there are always other flatheads willing to move into good spots. But I do believe you can reduce the average size of flatheads in a stretch of river by harvesting larger fish. Depending on conditions and food supply, it can take 20 years for a flathead to reach 20 pounds. Large fish aren’t replaced easily or rapidly.” Research shows that Fred the flathead leads a much more complicated life than many anglers suspect. He may travel only 10 miles or less in his entire life, or he may accumulate more than 1,000 “frequent swimmer” miles during annual spring and fall moves between winter and summer homes. He spent his first 5 years trying not to become food for his larger brethren, because 1- to 5-pound flatheads are regularly on the menu for larger flatheads. If he survives his first 15 to 20 years, he may actually be older than some anglers fishing for him. At 30 pounds he may be boss of his own logjam in a smaller river, and at 40 pounds he’s probably ruler of all he surveys—as long as there’s not a 50- or 60-pounder on the other side of his logjam.
Writer Dan Anderson, Bouton Iowa, is an avid angler who regularly contributes to In-Fisherman magazine on catfish topics.
