Bagarius rutilus

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

rutilus: from the Latin rutilus, meaning 'red', a reference to the orange fins in life and an allusion to the type locality (Red River).

Known from the from the Red River in northern Vietnam and Yunnan province, southern China, plus the Thái Bình, Sông Kỳ Cùng, Mã and Lam rivers in Vietnam and possibly the Nam Xam and Nam Ma drainages in Laos.

Type locality is 'Market in Hanoi, Vietnam'.

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 between March and June, and are often found congregating around the breeding grounds of other species, where prey is plentiful.

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.

Unrecorded in aquaria but in the wild eggs are apparently deposited in rocky crevices, are adhesive, and relatively large (1.1-1.4 mm diameter). Adults display broodcare during the incubation stage, remaining to guard the eggs from predation.

B. rutilus is uncommon in the aquarium trade although small numbers are occasionally exported. 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.

It can be told apart from congeners by the following combination of characters: cranium and interneural covered with numerous large, elongate tubercles; supraoccipital and interneural without sharp ridges; skin above neural spines anterior and posterior to adipose fin never forming distinct ridges; slender elongate neural spines; elliptical eyes; body depth at anus 11.0-12.3 % SL; head width 20.3-21.7 % SL; snout length 51.4-54.7 % HL; eye diameter 4.1-8.1 % HL; 12-13 pectoral-fin rays; 23-24 preanal vertebrae; orange fins in life.

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.