Catfishes: Siluriformes

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CATFISHES: Siluriformes

CANDIRU (Vandellia cirrhosa): SPECIES ACCOUNTS


More than one-tenth of living fishes are catfishes. Most catfishes have one to four pairs of barbels (BAR-buhls) around the mouth. These threadlike structures have many taste buds, which help the fish gather food efficiently. Catfishes usually have spines at the front of the dorsal (DOOR-suhl) fin, or the fin along the midline of the back, and the pectoral (PECK-ter-uhl) fins, the front pair. The spines in some catfishes are venomous and give off poison. Most catfishes are scaleless.


Catfishes live all over the world except Antarctica.


Most catfishes live in freshwater. Some live in estuaries (EHS-chew-air-eez), or the area where a river meets the sea, and others go into even deeper ocean water.


Most catfishes are bottom feeders and mainly eat invertebrates (in-VER-teh-brehts), or animals without backbones. Some catfishes eat fish, and some feed on fallen leaves and trees as well as algae (AL-jee), which are tiny plantlike growths that live in water and have no true roots, stems, or leaves. Some catfishes eat the blood of other fish.


Catfishes are generally bottom-dwelling. They are solitary, living alone, and are nocturnal (nahk-TER-nuhl) and active at night. Some, however, live far away from the bottom, are active during the day, and may form schools. Catfishes usually engage in courtship activity before spawning, or releasing eggs. They then provide some parental care. Most guarding of eggs and the young is done by males. Sea catfishes carry their eggs in their mouths until they hatch.


Catfishes are used as food and aquarium fishes.


Candirus can confuse the outward flow of nitrogen-rich water from a fish's gills with the outward flow of nitrogen-rich urine from a person urinating underwater. The candiru swims up the urinary tract, feeding on blood. The tight space and the spines of its head make it impossible for the fish to turn around or back out, and it dies inside the person, blocking urination and causing extreme pain, massive infection, shock, and often death. Humans who live on the candirus' rivers protect themselves by wearing tight clothing when swimming and by not urinating underwater.

Did You Know?

Mississippi produces 72 percent of the channel catfish farm-raised in the United States.


The World Conservation Union (IUCN) lists one catfish species as Extinct, nine as Critically Endangered, six as Endangered, twenty-two as Vulnerable, and four as Lower Risk/Near Threatened. Extinct means no longer in existence. Critically Endangered means facing extremely high risk of extinction in the wild in the near future. Endangered means facing very high risk of extinction in the wild in the near future. Vulnerable means facing high risk of extinction in the wild. Low Risk/Near Threatened means at risk of becoming threatened with extinction in the future. The U.S. Fish and Wildlife Service lists three catfishes as Endangered, or in danger of extinction throughout all or a significant portion of its range, and two as Threatened, or likely to become endangered in the near future.


Physical characteristics: Channel catfish are about 3 feet, 11 inches (1.3 meters) long and weigh about 58 pounds (26 kilograms). The mouth has four pairs of barbels. The adipose fin is small and far from the caudal fin, which is deeply forked. The spine on each pectoral fin has sawlike teeth at the end. Young channel catfish are mottled and brownish on the back and whitish on the belly. Adults are mainly deep brown.

Geographic range: Channel catfish live in North America east of the Rocky Mountains.

Habitat: Channel catfish live on the sand, gravel, and rock bottoms of clear streams and medium to large rivers with swift currents. They also live in quiet waters of lakes, reservoirs, and ponds. They may enter waters that have a low salt content.

Diet: Channel catfish eat small fishes; crustaceans (krus-TAY-shuns), water-dwelling animals that have jointed legs and a hard shell but no backbone; insects; and mollusks (MAH-lusks), animals with a soft, unsegmented body usually covered by a hard shell.

Behavior and reproduction: Channel catfish are bottom dwellers. They travel upstream in the spring and downstream in the fall. Spawning occurs during the day in nests guarded by the male. The eggs hatch in six to ten days. Channel catfish mature in two to five years when they are about 1 foot (30 centimeters) long. They live about sixteen years.

Channel catfish and people: Channel catfish are actively farmed and are a top sport fish.

Conservation status: Channel catfish are not threatened or endangered.


Physical characteristics: Squarehead catfish are about 9 inches (23 centimeters) long. The head is broad and flat, almost square, with a deep groove on top. The mouth is very wide and has wormlike appendages that are not barbels, in addition to three pairs of small barbels. The body narrows toward the rear. The dorsal fin has a short spine. The adipose fin is a low ridge that flows into the tail fin. The pectoral fin has one notched spine. There is a row of fringe above the lateral (LAT-uhr-uhl) line, which is a series of pores and tiny tubes along each side of the body used for sensing vibrations.

Geographic range: Squarehead catfish live in India, Bangladesh, and Nepal.

Habitat: Squarehead catfish live on the soft bottoms of rivers, canals, ponds, and flood plains.

Diet: Squarehead catfish eat other fish, sometimes fish half as large as they are.

Behavior and reproduction: Squarehead catfish lie still on the soft bottom of the river bed. They sometimes move their barbels in a jerky motion to lure small fish near their large mouth. Scientists are not sure how squarehead catfish reproduce.

Squarehead catfish and people: Squarehead catfish are commonly fished but are not eaten, probably because they look strange. They are sometimes used in aquariums. The dorsal spine can inflict painful wounds if the fish is stepped on.

Conservation status: Squarehead catfish are not threatened or endangered. ∎

CANDIRU (Vandellia cirrhosa): SPECIES ACCOUNTS

Physical characteristics: Candirus are 1 inch (2.5 centimeters) long. The body is naked and eel-like. There are spines on the gill covers, the mouth is suckerlike, and the lower jaw is toothless. Candirus are yellowish or almost clear.

Geographic range: Candirus live in South America.

Habitat: Candirus live in freshwater. They burrow in sandy bottoms.

Diet: Candirus eat the blood of other fishes.

Behavior and reproduction: When a fish opens its gill cover to expel water, the candiru enters, lodges itself using its spines, bites off the tips of the host's gill filaments, gorges itself with flowing blood, and drops off to the bottom. The entire process takes 30 to 145 seconds. Scientists are not sure how candirus reproduce.

Candirus and people: Candirus can swim up the urinary tracts of people.

Conservation status: Candirus are not threatened or endangered. ∎



Berra, Tim M. Freshwater Fish Distribution. San Diego: Academic Press, 2001.

Gilbert, Carter Rowell, and James D. Williams. National Audubon Society Field Guide to Fishes: North America. New York: Knopf, 2002.

Web sites:

"Understanding Catfish." The Content Well. (accessed on September 25, 2004).

"Vandellia Cirrhosa: Candiru." FishBase. (accessed on September 25, 2004).