Bagarius yarrelli

Bagarius: from 'Vaghari', a local name in Calcutta (Kolkata).

yarrelli: named for fellow zoologist and friend of the author William Yarrell (1784-1856).

Currently considered to have a wide but disjointed distribution extending southeastward from the Indus River, Pakistan, and including the Ganges and most major rivers of the Indian peninsula, Nepal, and Bangladesh, plus the Irrawaddy and Salween in Myanmar, the Mekong system in Laos and Cambodia, Chao Phraya in Thailand, several rivers of the Malay Peninsula, and the Greater Sunda Islands (the syonyms Bagarius lica and B. nieuwenhuisii were described from Sumatra and Borneo, respectively).

This distribution appears doubtful, however, and it seems likely that future studies will reveal that Indian and Southeast Asian populations are not conspecific with several species possibly involved (see 'Notes').

Type locality is 'Mota Mola at Poona, Deccan, India', referring to the Mutha Mula River at Pune, Maharashtra state, western India.

Inhabits large river channels and typically associated with fast-flowing, turbulent rapids where it takes shelter among boulders and large rocks. Juveniles may be found in smaller tributaries.

Adults perform seasonal spawning migrations when rivers swell and become turbid, and in the Mekong have been observed to move in large groups.

Suitable only for public installations or the very largest, highly-specialised private aquaria.

Prefers dim lighting and access to refuges in the form of driftwood, large rocks or lengths of plastic piping.

A large, mature filter system, rigorous maintenance regime comprising weekly water changes of 50-70% tank volume, and provision of highly-oxygenated water with plenty of movement should be considered mandatory.

An obligate predator feeding on smaller fishes, amphibians, crustaceans and other invertebrates in nature but in most cases adapting well to dead alternatives in captivity.

Young fish can be offered chironomid larvae (bloodworm), small earthworms, chopped prawn and suchlike while adults will accept strips of fish flesh, whole prawns/shrimp, mussels, live river shrimp, larger earthworms, etc.

This species should not be fed mammalian or avian meat such as beef heart or chicken since some of the lipids contained in these cannot be properly metabolised by the fish and may cause excess fat deposits and even organ degeneration.

Similarly there is no benefit in the use of 'feeder' fish such as livebearers or small goldfish which carry with them the risk of parasite or disease introduction and at any rate tend not have a high nutritional value unless properly conditioned beforehand.

Best maintained alone.

This species is also known as the 'giant devil catfish', 'giant painted catfish', and 'sand shark', and is fished for food across much of its range.

It is clearly unsuitable for the home aquarium given its eventual size and natural behaviour, and we know of only a handful of private aquarists with the facilities required to house it long-term.

Following Roberts (1983) B. yarrelli and B. bagarius can be distinguished from other congeners by the following characters: cranium and predorsal plate covered with horny skin differentiated into elongate unculiferous plaques; supraoccipital crest and predorsal plate without sharp ridges; skin on sides of head and on body with elongate unculiferous plaques similar in shape but generally smaller than those on dorsal surface of head; body depth 4.7-8.5 (mean 6.0); no large darkly pigmented spot or blotch on side of body between darkly pigmented areas near dorsal and adipose fins.

B. yarrelli can be told apart from B. bagarius as follows: pelvic-fin origin usually posterior (vs. anterior in B. bagarius) to a vertical line through base of last dorsal-fin ray; adipose-fin origin anterior to, on, or slightly posterior (vs. slightly to markedly posterior) to a vertical line through anal-fin origin; total external gill rakers on first gill arch 8-11 (vs. 6-9); pectoral-fin rays 11-14 (vs. 9-12); elongate neural spines 2-5, slender (vs. 4-8, distally expanded); abdominal vertebrae 21-24 (vs. 17-20).

The genus Bagarius is distinguished from all other genera in the putative subfamily Sisoridae by having markedly heterodont teeth in the lower jaw. Teeth are present in two or three outer rows of relatively numerous, close-set conical teeth, and one or two inner rows of less numerous, widely separated, and much larger conical teeth (vs. dentition of the lower jaw consisting of only small conical teeth, or a roughened bony plate).

The grouping currently contains four species but is in urgent need of review with a number of additional taxa thought to exist and B. yarrelli possibly representing a synonym of B. bagarius.