Flathead Catfish

Quick Take

• Flathead catfish break a rule that almost every other catfish follows, and that difference changes everything about how you'd catch one. Live-only feeding habits →
• After spawning, the male's behavior toward the female takes a dramatic and unexpected turn. Male guarding behavior →
• When flathead catfish enter a river where they don't belong, the consequences for native species are far worse than most people realize. Native species damage →
• Eating a flathead catfish isn't always as straightforward as it seems. Where you catch it could matter more than how you cook it. Contamination and consumption advisories →

The flathead catfish is a large, common species that is not known for its looks. They are freshwater catfish, and fishermen often hook large specimens that put up a tough fight. These catfish play a role in commercial and recreational use and can be a decent meal if fished from a clean environment.

Flathead catfish inhabit many regions where they occur naturally or are introduced, and can grow relatively quickly. They commonly reach 3 to 4 feet in length, and it’s not uncommon for fishermen to catch specimens exceeding 100 pounds, with the world record standing at 123 pounds. However, even in pristine waters, catching a flathead catfish weighing over 50 pounds is considered a notable achievement.

Three Amazing Flathead Catfish Facts

• Flatheads are solitary fish, making it difficult to breed them in typical captivity; however, they can mate in large ponds. They spawn when the water temperature starts to rise, which is usually late spring.
• Most catfish are scavengers, but flatheads are not; they only prey on live fish. Juveniles mainly eat invertebrates like insects, worms, and crayfish.
• In Texas, flathead catfish are the second-largest sport fish; the biggest is the blue catfish.

Classification and Scientific Name

The flathead catfish’s scientific name is Pylodictis olivaris, and it belongs to the Order Siluriformes. They occur inland or in coastal waters on every continent except Antarctica.

Siluriformes are most diverse in tropical regions like Asia, South America, and Africa. But one family occurs in Europe and another in North America.

The Americas are home to more than half of the species, and only freshwater species inhabit Madagascar, Australia, and New Guinea.

Flathead catfish are members of the Family Ictaluridae, which includes 49 species. They are the largest family of freshwater fishes native to North America.

They are easily recognized compared to other North American freshwater fishes. Their two most significant identifying features are four pairs of whiskers (barbels) around the mouth and the absence of scales.

Unlike other large groups of North American freshwater fishes, such as darters, minnows, and suckers, which are diurnal, members of the family Ictaluridae are primarily nocturnal.

Appearance

It is not hard to distinguish a flathead catfish from other species. Their tails are squared and forked, and they have large, flattened heads with long bodies. Medium to large specimens often have potbellies, beady eyes, and broad heads.

Their eyes highlight the flatness of their heads, which are distinctly flat and oval-shaped. Their lower jaw also draws attention to their heads because it protrudes beyond the upper jaw. Finally, unlike other catfish species, the flathead’s anal fin is short, with only 14 to 17 fin rays.

The flathead catfish’s color differs depending on their environment, but it is primarily mottled with varying shades of brown and yellow sides, and its belly is mottled white. In addition, flathead catfish have sharp, heavy dorsal and pectoral spines and long whiskers next to their mouths.

They can grow to lengths of 61 inches and tip the scales at 123 pounds, which makes them the second-largest North American catfish after the blue catfish (Ictalurus furcatus). However, their average length is around 25 to 46 inches.

Behavior

The flathead catfish prefers the deeper parts of lakes and rivers. They ambush their prey, waiting under cover until their prey comes closer. Flatheads are nocturnal; however, they are also sometimes active during the day.

In addition, they are primarily piscivorous, meaning their diet consists mainly of fish, and they are known for eating other game fish in areas where they are an invasive species. However, when the water temperature drops below 58°F, they become inactive.

Habitat

Flathead catfish occur mainly in large bodies of water, like big rivers and reservoirs. They prefer deep pools in rivers where there is calm water flow. In addition, they like depressions or holes that exist in eddies and adjacent to bridge pilings.

Another popular habitat is tailraces below dams. Their ideal hiding spot often has a hard bottom and possibly has timber or driftwood in it.

However, in large reservoirs, flathead catfish mainly occur in deeper areas, usually in old river beds and near the headwater tributary.

Diet

Flathead catfish are opportunistic omnivores that eat a variety of available food. They are mainly bottom feeders and prey on animals like:

• Insects
• Crayfish
• Clams
• Shiners
• Gizzard shad
• Bullheads
• Carp

In addition, they feed on terrestrial animals that dare to come too close to the water. The best bait to use when trying to catch a flathead catfish is live fish, more than for other catfish species. Surprisingly, unlike most catfish, they seem to be deterred by old, stinking bait.

While these fish are active during the day, they are primarily nocturnal and spend their days inactive in the deep water, hidden under cover. Then, as it starts to get dark, they migrate to shallow water to feed.

Predators and Threats

The only predators that prey on flathead catfish are members of their own species and humans who catch them for commercial and recreational purposes. However, larvae and juveniles are susceptible to attacks from wading birds like herons and other birds of prey that inhabit the forage in streams and rivers.

Flathead catfish have no known threats. Their population is stable at the moment, but pollution and sport fishing could lead to a decline in numbers.

No conservation efforts are in place to protect the flathead catfish, and they are listed as a Least Concern on IUCN’s Redlist.

Reproduction, Babies, and Lifespan

While the flathead catfish’s mating systems have not been documented in the wild, scientists have observed them in captivity. During reproduction, the male will move over and around the female while rubbing her with his belly and barbels (whiskers).

Next, the males stop swimming with their tails surrounding the female’s head and start to convulse. They repeat this behavior frequently until the female begins to spawn, which takes around 14 days.

When captive females spawn, they deposit their eggs in a depression made in the aquarium gravel. Lastly, the eggs are fertilized by the males.

Spawning takes approximately 4 hours, and males become incredibly aggressive and start defending the eggs, even from the females who laid them.

Mating System

Flathead catfish are monogamous, and their sexual maturity depends on their environment. However, it usually ranges from 3 to 5 years in females and 3 to 7 years in males.

Females spawn during the summer when the water temperature rises between 75°F and 80°F. Their eggs start to hatch between 6 and 9 days after fertilization.

Flathead catfish construct nests under cover, which include brush piles, stumps, rock outcroppings, and logs. The number of eggs females lay depends on their body size, but a single nest can host up to 100,000 eggs. The eggs stick together in clusters and are expelled in masses of 30 to 50 eggs.

Lifespan/Longevity

The flathead catfish has an average lifespan of 5 to 22 years. However, they can live up to 28 years. Scientists can tell their age from their pectoral spine and otolith age estimates. Because these catfish are so large, they are not often kept in captivity.

Population

Because this species has a large number of subpopulations in various locations, it is hard to determine the total population size.

However, IUCN’s Redlist listed them as Least Concern with a stable population. But, due to severe pollution, their numbers have likely declined over the last ten years.

Ecosystem Roles

The flathead catfish is one of the main predators of other fish species in their habitats and can be invasive in areas where they do not naturally occur. In addition, they play host to over 25 different parasitic species, including:

• Nematodes
• Leeches
• Platyhelminth worms
• Copepods
• Fresh mussel larvae
• Water lice

Fishing

Flathead catfish are a sought-after catch for anglers in lakes and rivers. They also provide a tough fight, making all the effort worthwhile. Larger specimens are often found in snag-filled environs and can take a while to subdue. Heavy tackle with live bait is needed to catch one of these fish.

Impacts

When flathead catfish were introduced into new states, researchers saw a massive decline in native fish populations, making them a threat to biodiversity. For example, when they were introduced to the Altamaha River in Georgia, they decimated the bullhead catfish population, and researchers saw an 80% reduction in the number of redbreast sunfish.

In addition, flatheads have eliminated native catfish numbers in the coastal North Carolina rivers and still prey on shad and crayfish. They also threaten crabs and American eels that share their habitat.

Some findings suggest that flathead catfish predation may obstruct restoration efforts of sturgeon, shad, American eel, and striped bass in the Delaware Estuary.

Health Risks

Eating a flathead catfish could be risky because they are susceptible to contaminants like polychlorinated biphenyls, which cause rashes and are poisonous. This is why the Commonwealth of Pennsylvania advises that eating flatheads caught in the lower Schuylkill River should be limited to once a month. However, more testing is required to determine how safe eating flatheads from other environments is.

Prevention and Control

Researchers believe that electrofishing and intense sport fishing may help diminish flathead populations in areas where they do not naturally occur, so native fish species can survive. In Delaware and Susquehanna, anglers are asked not to release them when caught, regardless of size.

Aquariums

It is tough keeping a flathead catfish in captivity; however, it is not impossible. They need a large enough aquarium with many hiding places, which you can provide with a few stones, large roots, and bogwood.

Flatheads grow quickly, so you must consider that when choosing the size of your aquarium. Unless your aquarium is extremely large, only one adult male should be kept. In addition, their tankmates need to be big enough so that the flatheads can’t eat them.

Because flatheads eat a lot, the aquarium must be well-filtered; otherwise, water quality will suffer. In addition, the pH level in the tank must be 6-8, and the temperature around 77-82°F.

Like many other catfish species in captivity, flatheads eat almost anything and are very easy to feed. They will accept various dead food (even without training), but their primary diet in the wild consists of catfish and other small fish species. In addition, they also prey on terrestrial animals like young birds, frogs, and crayfish.

Breeding flathead catfish in captivity is close to impossible because of their solitary nature, but they do breed in large ponds. In their natural habitats, flathead catfish spawn towards the end of spring when the water temperature starts to rise.