Fish-eating machine: Flathead catfish biology

Catfish are big, dumb fish that eat the most disgusting stuff that falls to the bottom of the lake floor, right? Not in the case of flatheads.

Call them what you will — Appaloosa, goujon, yellow cat, shovelhead, mud cat or any of a half dozen other names — the flathead catfish is rightfully the king of the aquatic jungle. While they share some characteristics with blue and channel cats, they are, in many ways, a different breed of cat.

Historically, flathead catfish roamed the entire Mississippi, Missouri and Ohio river basins with populations in all states west of the Appalachians and east of the Rockies. In Mississippi, the flathead shares rivers, streams and reservoirs with blue and channel catfish.

Like blues and channels, flatheads spawn in cavities when water temperatures top 70 degrees. The egg masses, diligently and aggressively guarded by the male, often contain more than 100,000 eggs.

After hatching, the young feed on a variety of invertebrates. Young flatheads transition to fish at lengths as small as 1 inch and, in most waters, feed almost entirely on fish by the time they reach 6 to 8 inches. Unlike blue and channel cats that eat a wide variety of vertebrates and invertebrates, and even grain when available, adult flatheads feed almost exclusively on live fish.

And they are fish-eating machines. I’ve collected mid-sized flatheads with a half-dozen freshly ingested, keeper-sized sunfish, nicely arranged like shingles on a roof, in their stomachs.

What fish eat is determined by mouth width; biologists call this gape. A fish can consume prey fish with a body depth less than the gape. Of all freshwater fish, flathead catfish have the greatest gape-to-body-length ratio. Flathead catfish can consume fish that are far larger than anything a largemouth bass can eat. A 3-foot-long flathead can eat the largest shad or sunfish. A 4-footer could consume George Perry’s world-record largemouth bass.

River-dwelling flatheads, unlike blues and channels, remain in the channel, rarely moving onto the floodplain when the river floods, and appear to avoid floodplain lakes. Although it seems quite a paradox, these river-loving fish thrive in reservoirs. The current world-record flathead — a 123-pound giant —was caught in Elk City Reservoir, Kansas, and the majority of state-record flatheads were caught in reservoirs.

The 77-pound Mississippi state record was caught in the Tenn-Tom Waterway, which is a series of reservoirs.

Flathead catfish in rivers demonstrate a strong preference for wood. Large rock seems to provide a suitable second home when large wood is scarce.

Early tag-recapture and radio-tracking studies, several of which were done in Mississippi waters, found that flathead catfish move very little, and they have long been considered the stay-at-home members of the catfish family. Several recent tracking studies also report limited movement, but research done by Jason Vokoun while a doctoral student at the University of Missouri found dramatically different results.

Vokoun collected, radio-tagged and intensively tracked adult flatheads in tributary streams to the Mississippi and Missouri rivers. The tagged flatheads moved upstream to smaller tributaries to spawn, then downstream to summer habitats in large tributaries. Most overwintered in the Mississippi and Missouri rivers, but some remained in deep tributary pools.

The reasons for different behaviors among systems aren’t apparent, but the differences are probably linked to annual habitat needs. Similar studies are needed in Mississippi waters because the management consequences are huge, especially as anglers are demanding better trophy catfish angling opportunities.

High length limits can be effective for producing more trophy flatheads. High length limits could be implemented on segments of rivers where flatheads move little, but seasonal or system-wide regulations may be needed to develop populations of big flatheads in rivers where they exhibit more migratory behaviors.

I don’t have a crystal ball and can’t see the future, but present trends suggest increasing angler interest in flatheads and greater management attention to this fish-eating giant. If you’ve never battled a big flathead on rod and reel, I strongly encourage you to give it a try.

About Hal Schramm 182 Articles
Hal Schramm is an avid angler and veteran fisheries biologist.

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