Big flathead catfish are something. The only North American freshwater predators that grow larger are alligator gar and sturgeons. Maybe the blue catfish. But they don’t match the flathead as a predator. Nor do other freshwater fish, for that matter. We would have to enter the saltwater league to find a tougher customer.
The native range of flathead catfish includes the larger rivers of the Mississippi, Missouri, Ohio, and Rio Grande river basins from the Great Lakes south into northern Mexico. Flatheads thrive in rivers that range from tributaries just 100 feet wide to the lower reaches of the nation’s largest rivers. Although rightly called a warmwater fish, flatheads also can survive and grow large in cool waters. In 1978, the first flathead ever caught in Canada was taken in a commercial trap net on the Ontario side of Lake Erie. And the Minnesota state record stands at 70 pounds, larger than the Georgia record.
Flathead catfish inspire tales both tall and true, as they rank among the largest North American freshwater fish, and their slightly monstrous appearance (to the uninitiated) makes them formidable gamefish. A 30-pound fish is beyond the realm of experience for nearly all freshwater anglers. So when one breaks a bass fisherman’s line, its estimated size increases in direct proportion to the diameter of the fisherman’s eyeballs when the fish spools him.
Most rivers in the flathead’s original range have been dammed, creating large impoundments that provide good habitat. Gizzard and threadfin shad abound, providing prey for all sizes of cats. Sunfish species, bullheads, and skipjack herring add to the smorgasbord.
These species also occur in rivers, plus many species of large suckers that slide smoothly down a flathead’s gullet. While studying the diet of flatheads in the Flint River, biologists were surprised to find even big fish scarfing young-of-the-year shad less than an inch long. They’d upchuck this partially digested shad soup in the livewell.
The big flatties must have cruised through the schools with their mouths open like a pod of baleen whales. Flatheads in this limestone-based river also consumed lots of crayfish, the most common prey for fish under about 10 pounds.
Not surprisingly, flatheads grow fast, generally faster in terms of weight than any predatory fish on the continent, exceeded in some systems only by the common carp and grass carp. Their fastest growth spurt typically occurs between ages 3 and 8 when they add several pounds a year. But even big fish grow fast, with tag returns indicating increases of more than 10 pounds per year, in some cases. Record-size flatheads haven’t been aged, though they certainly can live at least 20 years.
