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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

Flathead catfish have fearsome, crushing plates at the rear of the mouth to ensure no escape for their prey. © John Lyons
Flathead catfish have fearsome, crushing plates at the rear of the mouth to ensure no escape for their prey.

© John Lyons

February 2007

Felines with fins

Long disparaged as the strays of the piscine world, Wisconsin's bullhead catfish deserve some respect.

Joe Hennessy

Meet the species
Cats with an image problem
"Kittens" that play hide and seek
Big cats on the prowl
Wisconsin's bullhead catfishes

There is a species of fish that never looks at the clothes of the angler who throws in the bait, a fish that takes whatever is thrown to it, and when once hold of the bait never tries to shake a friend, but submits to the inevitable...That is the fish that the State should adopt as its trademark, and cultivate friendly relations with, and stand by. We allude to the bullhead...

– "In Defense of the Bullhead," by Wisconsin Governor
George W. Peck (1840-1916)

It seems curious that a statesman would pen a treatise extolling the virtues of the lowly bullhead. Such distinctions usually are reserved for "more dignified" fish, like trout, whose perceived nobility arises only from the tweed jackets of its pursuers and the insistence of those anglers on capturing the quarry with a great deal of fluff. I digress. Let us return to the basics, and examine the nature of the bullhead. Then you, reader, may make your own judgment.


Ictaluridae is the Latin name for the bullhead catfishes. Mysterious, whiskered creatures with beady little eyes, the Ictalurids are the largest family of freshwater fish entirely native to North America. The family has existed for more than 60 million years, with records dating to the Paleocene Era. Among fish families found in Wisconsin, only the sturgeon, bowfin, and paddlefish are older.

In Wisconsin, the representatives of the family include the familiar bullheads, channel and flathead catfish, and three small, reclusive species of madtoms. Our state is perched near the northern reach of the ranges of all eight of these species, so while some are locally popular or abundant, the attention afforded bullhead catfish is generally small compared to other Wisconsin fish, and the best-known members of the family – the channel and flathead catfish – don't enjoy the widespread glamour and status here that they do in Southern states.

bullhead catfishes
Flathead catfish Pylodictis olivaris
Channel catfish Ictalurus punctatus
Black bullhead Ameiurus melas
Yellow bullhead Ameiurus natalis
Brown bullhead Ameiurus nebulosus
Slender madtom Noturus exilis
Tadpole madtom Noturus gyrinus
Stone cat Noturus flavus

All species in Wisconsin possess eight soft barbels around the mouth – the whiskers that give catfish their name. Delicately soft and utterly harmless, barbels extend the fishes' senses of taste and touch. With mottled skin in beautiful hues of brown, black, gray and yellow, smooth and only slightly slimy to the touch, Ictaluridae is one of the few truly scaleless families of freshwater fish in North America.

The entire skin of a catfish – head, whiskers and body – is peppered with taste buds. It has been estimated that there are more than 100,000 on the skin of a black bullhead. Taste and touch are intricately related in catfish, playing almost indistinguishable roles in how food is located and assessed before ingestion. (Some have described Ictalurids as "swimming tongues.") The fish are able to detect chemical stimuli emanating from food from many fish-lengths away, according to George Becker, author of Fishes of Wisconsin.

Other obvious features shared by Ictalurids are their hard, pointy spines on the pectoral and dorsal fins. It's the spines, not the whiskers, which you have to watch out for when handling these fish. The "spines" of a catfish are embryonically fused soft fin rays, sharply serrated, which can be locked into place in a defensive posture. To top it off, all madtoms and some bullheads have poison glands at the base of their spines, which intensify the wounds the fish can inflict.

With their unparalleled senses of taste and touch, Ictalurids are also very sensitive to sound. Ictalurids have Weberian ossicles – distinctive bony connections between their swim bladder and inner ear – that place them among a group of fish called ostariophysans. All fish can detect vibrations through their lateral lines (the line of cells along the side of the body that responds to movement of water); in ostariophysans, the solid connection between the swim bladder and inner ear greatly enhances the range of sounds the fish can detect and their sensitivity to sound.

The exquisitely developed senses of taste, touch and hearing in catfish are wonderful adaptations for life and feeding in the dark, when the bullhead catfishes are most active. It's an interesting contrast to another night-feeder, the walleye. The walleye has large eyes with features specially adapted to collect light very efficiently, but evolution in catfish has eschewed sight in favor of the other senses.

Dispense with the image of catfish blindly rooting around for food on the bottom in the dark. While there are a few families of catfish in the world that actively suck bottom matter while feeding, Ictaluridae are not among them. While "bottom feeder" might be an apt description, "scum sucker" most certainly is not. Ictalurids are carnivores, and though the diets of different species vary, they include fish, insects, frogs and crayfish. Many species will scavenge on dead animals, but the stinky baits used by some anglers to catch catfish are more about overloading the fishes' senses of taste than their predilection for rotten food.

Meet the species

Wisconsin's Ictalurids can be classed into three broad groups. The bullheads – yellow, brown and black – are closely related members of the genus Ameiurus. The madtoms – slender, tadpole and stonecat – all belong to the genus Noturus. The two large catfish – the channel catfish and flathead catfish – are not closely related, but are linked by their importance as sport and commercial species.

Cats with an image problem

Of all Wisconsin's Ictalurids, the bullheads are probably both the most familiar and most misunderstood. Some people see them as "dirty" undesirable fish, while others prize them for their local abundance and sweet flesh – described by some as "poor man's lobster."

The diversity of opinion partially stems from one of the strengths of the group: bullheads are amazingly resilient. All three species in Wisconsin are generally found in shallow lakes and ponds, backwaters of rivers, and slow-moving rivers. Within these types of habitat, bullheads tolerate much more disturbance and degradation than many other species; their ability to endure low dissolved oxygen, agricultural and urban siltation, and some industrial pollutants gives the impression that they are "dirty water" fish. Bullheads can live in some relatively foul places. That hardiness shouldn't be confused with any preference for such abodes. Nor should the mere presence of bullheads be seen as an indicator of degraded water conditions. However, if bullheads dominate a particular fish community it could be a sign that water quality is less than ideal.

A proper characterization of prime bullhead habitat is warm, weedy water less than ten feet deep, with soft bottoms comprising mud, silt and sand. During spawning, all three species build nests – usually shallow excavations under matted detritus and vegetation. Female bullheads construct the nests, but male bullheads provide much of the parental care. Among North American freshwater fish, bullheads provide one of the highest levels of parental care. The male bullhead will collect the eggs in its mouth and roll them around to oxygenate them. After hatching, young bullheads can be seen swimming in large compact schools. What's often missed by the casual observer is that the parents are nearby, maneuvering to keep the school together. During winter, bullheads of all sizes "mud up" – burrow into the soft bottom of their habitat for some warmth, leaving only a small opening above their mouths to breathe.

At first glance the yellow, black and brown bullheads look alike, but you can easily determine which fish is in hand. First, look at the chin whiskers: If they're yellow or white, you've got a yellow bullhead. If they're black or gray, you've got a black or brown bullhead. In black bullheads, the membranes between fin rays are jet black, but not so in the brown bullhead. Brown bullheads have distinctly mottled skin; black bullheads have solidly dark skin. Finally, brown bullheads have razor-sharp serrations on their pectoral spines – the same spines that poke you can also give you nasty scratches, to complete your fish-handling pleasure. The serrations are rounded, if present, on the pectoral spines of black bullheads.

"Kittens" that play hide and seek

Small, secretive, and relatively scarce in Wisconsin, a madtom would probably generate a puzzled look from most observers. "A little bullhead," most might say, unless the person is an angler who is familiar with the "willow cats" that are prized bait in the Mississippi River. Wisconsin's three madtom species represent a much larger group of catfish. There are approximately 30 species of madtoms in North America, most in the southern and southeastern United States. Besides myriad colorations, the madtom is also renowned for "the most virulent stings" administered by members of the Ictalurid family, according to ichthyologist Robert Jenkins.

Ictalurids range in size from 100-pound flatheads to the 3- to 4-inch slender madtom, a state endangered species. © John Lyons
Ictalurids range in size from 100-pound flatheads to the 3- to 4-inch slender madtom, a state endangered species.

© John Lyons

Wisconsin's madtoms prefer shallow, rocky riffles, and generally wriggle into crevices during the day, emerging after dark to terrorize aquatic insects and other small animals. Like the flathead catfish, madtoms will find a crevice or cavity in which to spawn, and are known to put sunken aluminum cans to good use. These fish are much more sensitive to habitat degradation than their bullheaded cousins, and the slender madtom is listed as a state endangered species. Agricultural, urban and suburban runoff and siltation of riffle habitat threatens madtom populations in Wisconsin streams.

Big cats on the prowl

The Ictalurid most commonly sought by Wisconsin anglers and commercial fishers is the channel catfish. Of legendary importance in the southern United States, the channel catfish enjoys great favor among its pursuers in Wisconsin as well. First described in 1818, the channel catfish has had at least 23 different scientific names, but contrary to legend, the renowned zoologist Constantine Rafinesque did not recommend Misteras whiskeras.

Channel catfish may be found in all three of Wisconsin's major drainages – the Mississippi River, Lake Michigan, and Lake Superior. It is most common in the Mississippi River and in the southern parts of the state. It prefers riverine habitat, but may be found in some lakes and reservoirs, and it is an opportunistic feeder, taking insects, fish, crayfish and amphibians. It is the single most important commercial species in Wisconsin waters of the Mississippi River.

The largest member of the catfish family plying Wisconsin's waters is the flathead catfish. Flatheads inhabit secluded shelters and dark places in Wisconsin's largest river systems. While the reputation of the muskellunge as a fierce predator is well documented, the flathead catfish proceeds with quiet, chilling efficiency, and its abilities as a predator are unsurpassed among Wisconsin fishes. It is the state's largest piscivore (fish-eater) and some fish may have historically exceeded 120 pounds in weight. The state record caught by hook-and-line was 74.5 lbs, in 2001 from the Mississippi River. In 1911, two fish caught by set line in Wisconsin were reported to weigh 118 and 125 pounds.

I, for one, would not call this fish a "bottom feeder" to its face. Young flatheads will eat insects and crayfish, but by the time they reach 10 inches they have switched to a diet consisting almost exclusively of live fish. Flatheads are not scavengers. The gaping mouth of a flathead is eerie to contemplate; a large man's hand is dwarfed by the capacity of the mouth of even a moderately-sized flathead. No razor-sharp teeth adorn the entrance to the cavity, but fearsome, crushing plates at the rear of the mouth ensure no escape for its prey.

DNR researchers Randy Piette, Al Niebur and Dave Bartz are learning about the long-term movements of flathead catfish in the Fox-Wolf system. During 2002-2004, 40 adult male flathead catfish were captured and outfitted with small radio transmitters. Males were chosen because male flathead catfish select and defend spawning sites, and handle all care of newly-hatched fish. Flying above the rivers and parts of the Lake Winnebago system with a radio receiver, the scientists were able to locate individual fish and plot their movements along the river.

Radio receivers track long distance catfish migrations from the air. © Al Niebur
Radio receivers track long distance catfish migrations from the air.

© Al Niebur

The investigators identified spawning site locations, summer and winter habitat preferences, and the timing and distance of adult male flathead catfish movement. By knowing where the fish stayed during the spawning season, DNR researchers could later dive at those sites and assess the depth, cover and bottom substrate of the spawning site.

What's been learned so far is that individual fish are likely to return to the same spawning site and winter habitat every year. This high degree of "site fidelity" was previously unknown, and has ramifications for management of the species. Choice winter habitat is often occupied by dozens or more flatheads. "We find them in relatively deep holes," said Piette, "and they will be quite concentrated – thirty or forty fish of all different sizes sharing a single area. The fish seem to require a certain depth, and enough current to keep the bottom scoured clean. There's no silt. The bottom is hard sand and gravel, with mussel shells and large pieces of wood scattered."

The researchers don dry suits and dive into the frigid, turbulent depths to wrangle catfish in these winter congregations."Wrangling" might be the wrong word: Piette says that once the water temperature is below 40 F, the fish are very lethargic. The divers choose and catch catfish by hand, put them into mesh bags, and haul the fish to the surface to be implanted with radio tags. "We're mainly capturing smaller fish this way," said Piette. "Tagging smaller individuals gives us an opportunity to learn about the behavior of juvenile catfish."

Overall, Piette thinks the Fox-Wolf flathead catfish population is below capacity for the system, but individual fish are in good condition for their length. Local fisheries manager Al Niebur adds that the fish are relatively slow-growing. Both see the flathead fishery as having fantastic potential for trophy fishing and consumption, but feel the current level of exploitation is too high for the fishery to truly meet its potential.

Niebur has been working with the Winnebago Catfish Advisory Committee, a citizen group formed in the late 1990s. Among their recommendations are ending the commercial flathead fishery in the Fox-Wolf system and lowering possession and daily bag limits for anglers. These biologists and concerned citizens are heeding George Becker's decades-old advice: "Little is known about the biology and the population structure of the flathead catfish in Wisconsin. To ensure sustained fishing and a viable population, a long-term, active research program is advised." Just as a closer look at the entire bullhead catfish family helps us appreciate how they have adapted to fill in an available niche in our fisheries.

Fisheries Biologist Joe Hennessy proposes policies and regulations to manage warmwater fisheries. When he isn't researching catfish biology, he occasionally hits the lakes and rivers to fish for them.