Are Catfish Really Bottom Feeders?

You're at the fish counter or a cookout, and someone wrinkles their nose: "Catfish? Those are bottom feeders." It's half true. Catfish often feed on the bottom, and the barbels around their mouths are built for searching it. But the big catfish people actually catch and eat, like channel and blue catfish, are omnivores that feed wherever food is. As they grow, they hunt live fish. Here is what catfish really eat, how they find it, and whether the "bottom feeder" label should change how you see the fish on your plate.

What catfish actually eat

The label suggests a fish that eats only muck. The diets of the most familiar species say otherwise.

Channel catfish eat crayfish, snails, clams, frogs, insects and plant matter. Young channel catfish are the most omnivorous. Adults over about 45 cm (18 inches) prey on other fish, such as yellow perch and sunfish. They feed by suction and swallow their prey whole. The largest channel catfish on record weighed 26 kg (58 lb) and was caught in South Carolina in 1964.

Blue catfish are what the Virginia Department of Wildlife Resources calls "omnivorous, or trophic generalist." They commonly eat small fish, crayfish, mollusks and plant matter. As they grow, they "transition to primarily consuming other fish." Research by Virginia Tech and Virginia DWR found that a blue catfish with unlimited food can eat roughly 8–9% of its body weight per day.

That appetite has consequences. Blue catfish are not native to Virginia's coastal rivers. They were first stocked there in 1974, and by 2023 they had been recorded in every Virginia tributary of the Chesapeake Bay. Virginia DWR now classes them as invasive. The state record blue catfish weighed 143 lb and came from Buggs Island Lake in 2011.

Neither species filter-feeds. A claim that blue or channel catfish strain algae or plankton from the water is simply wrong. An Alabama extension project on catfish farming notes that catfish "do not possess the feeding apparatus to filter" plankton.

How catfish find food

Catfish earned the bottom-feeder label because they are very good at finding food where other fish can't see it.

A channel catfish is covered in taste buds over "the surface of its entire body." The taste buds are densest on its four pairs of barbels, the "whiskers" around the mouth, at about 25 per square millimeter. A catfish can taste food before it touches its mouth.

Its sense of smell is just as sharp. The nasal organs of a channel catfish can detect some amino acids at about one part per 100 million. In murky river or pond water, smell and taste do the work that eyesight can't.

One myth worth dropping is that the barbels sting. They can't. The real hazard is the sharp spines on the pectoral and dorsal fins, which can injure anyone who grabs a catfish carelessly.

When and where they feed

Catfish feed on the bottom often, but not only there. Blue catfish are frequently nocturnal. In bright daylight they rest in deep holes. In low light they move into shallower water to forage. Channel catfish live in rivers, reservoirs, lakes and ponds.

These are freshwater fish. Pictures of catfish scouring the ocean floor don't apply to the species most anglers and cooks know.

The catfish that really is a bottom feeder

If any catfish deserves the label, it's the cory catfish of home aquariums. Corydoras belong to a different family from North American catfish. They are armored catfishes (Callichthyidae), native to South American fresh waters east of the Andes. The bullheads, madtoms, channel catfish, blue catfish and flathead catfish belong to the North American family Ictaluridae, which has roughly 48 to 51 species depending on who is counting.

Corydoras mainly eat bottom-dwelling insects, insect larvae and worms, which they find by working their barbels through the substrate. They also eat some plant matter and will scavenge dead fish. They can gulp air at the surface, which helps them survive in low-oxygen water.

If you keep them, their bottom-feeding habits affect their care:

• Use sand or fine gravel, which is gentle on their barbels.
• Feed sinking pellets or wafers so food reaches them on the bottom.
• Keep nitrate low. High nitrate can lead to barbel infections that leave the barbels short and useless.

A cory is not a cleanup crew that lives on leftovers. It needs food meant for it.

Does bottom feeding make catfish less safe to eat?

This is usually what the "bottom feeder" comment is really about. Two facts matter here.

Catfish sold in the U.S. are inspected by the USDA's Food Safety and Inspection Service, the agency that inspects meat and poultry. A 2015 final rule created a mandatory inspection program for domestic and imported catfish (the order Siluriformes), carrying out provisions of the 2008 and 2014 Farm Bills. FSIS began reinspecting imported fish products on August 2, 2017.

On mercury, the 2017 FDA/EPA fish advice placed catfish among the "Best Choices," the lowest-mercury group, at an average of 0.15 micrograms per gram or less. That group is recommended at two to three servings a week. Check FDA's current chart for the latest guidance.

The verdict

Catfish do feed on the bottom, and their bodies are built for it. "Bottom feeder" still undersells them. Channel and blue catfish are opportunistic omnivores that hunt at night, move between deep and shallow water, and become fish-eating predators as they grow. The cory catfish in an aquarium comes closest to the label, and even it needs real food. For the catfish on your plate, the bottom-feeder reputation says little about safety. Federal inspection and low mercury levels say much more.

Sources (13)

• Channel catfish – Wikipedia
• Blue Catfish – Virginia Department of Wildlife Resources
• Virginia Sea Grant – blue catfish feeding research
• SARE project FS00-122
• Catfish Senses and Sensibilities – In-Fisherman
• Ictaluridae – Florida Museum
• Ictaluridae – Tree of Life Web Project
• Corydoras – Wikipedia
• Corydoras Catfish Care Guide – Chewy
• FSIS Directive 14,950.1
• New Rules Announced for Catfish Inspections – Food Safety Magazine
• EPA and FDA Issue Final Fish Consumption Advice
• EPA-FDA Fish Advice: Technical Information