B. gigas is reportedly from the Eocene of Sumatra, but the age of the locale has been questioned. The oldest known confirmed sisorid fossil is B. bagarius found in Sumatra and India of the Pliocene.
Description
Bagarius species have a broad head that is moderately or strongly depressed. The mouth is broad and terminal or slightly inferior. The gill openings are wide. The dorsal fin and pectoral fins have strong spines. The dorsal fin spine is smooth, and the pectoral fin spine is smooth anteriorly and finely serrate posteriorly. The dorsal, pectoral, and caudal fin lobes sometimes with filamentous extensions. The head and body is entirely or almost entirely covered by heavily keratinized skin superficially differentiated into unculiferous plaques or tubercles. Bagarius species lack a thoracic adhesive apparatus and paired fins are unplaited. Bagarius species have the same general colour pattern consisting of three darkly pigmented bands or blotches on the body. Irregularly placed spots may also be present on the body. The fin pigmentation varies from species to species, from plain, to spotted, to slightly or heavily barred. Also, some B. yarelli may have a heavily spotted pattern like a Dalmatian dog that obscures the main barred pattern. In B. bagarius, the pelvic fin origin is normally anterior to a vertical line through the base of the last dorsal fin ray, while in B. yarelli the pelvic fin origin is posterior to this vertical line. Also, in most B. bagarius, the adipose fin originates far back over the anal fin, on a vertical through the base of the third or four anal fin ray. However, in most B. yarelli, the adipose fin originates near or in front of a vertical line through the anal fin origin. In B. suchus, the adipose fin originates even further back than in B. bagarius or B. yarelli. B. suchus tends to have a flatter head and body than either B. bagarius or B. yarelli. B. bagarius does not grow much past 20 centimetres SL. B. rutilus grows to about 100.0 cm SL. B. suchus grows to about 70.0 cm SL. B. yarelli grows very large, reaching about 200 cm SL.
Ecology
B. bagarius inhabits rapid and rocky pools of large and medium-sized rivers. B. suchus is usually associated with rapids in the large rivers it inhabits. B. yarelli occurs in large rivers on the bottom, even with swift current, never entering small streams. It is found among boulders, often in the white water of the rapids where it apparently is indifferent to the strong current. B. bagarius is primarily entomophagous. It also feeds on small fishes, frogs and shrimps. B. suchus, however, is a piscivore. B. yarelli feeds primarily on prawns but also eat small fishes and aquatic insects. B. bagarius and B. yarelli breed in rivers prior to the beginning of the annual flood season. B. yarelli migrates in schools. It is reported to migrate to follow its prey. It is also reported that it follows Catlocarpio siamensis during its upstream migration. Apparently the main upstream migration begins close to the peak of flood, when the current is very strong and the water is turbid.
Relationship to humans
Bagarius species are marketed fresh, and are important as a food fish, but the meat spoils rapidly and can cause illness. The Goonch catfishB. yarrelli has become an object of media attention as reports have surfaced of some of these fish feeding on funeral pyres in the Kali River. There is speculation that some drownings have also been caused by large specimens that have "developed a taste" for human flesh from the corpses and subsequently have attacked bathers in the river. This is the subject of a TV documentary aired on 22 October 2008, as well as an episode about the Kali River goonch attacks on the Animal Planet series River Monsters.
