Brachygobius nunus (HAMILTON, 1822)

SynonymsTop ↑

Gobius nunus Hamilton, 1822; Gobius alcockii Annandale 1906; Gobius bombayensis Annandale, 1919

Classification

Order: Perciformes Family: Gobiidae

Distribution

Type locality is the ‘river below Calcutta’ which corresponds to the western side of the Ganges River delta south of Kolkata, West Bengal state, with reports as to its wider distribution varying significantly.

It’s sometimes said to be present throughout India plus both mainland and maritime southeast Asia, but is more likely restricted to India, Bangladesh, Sri Lanka, and possibly Myanmar.

Habitat

Inhabits both fresh and brackish water, and generally restricted to lowland, coastal environments including mangrove swamps, estuaries, and tidal streams.

Substrates thus tend to be composed of mud, sand and silt with overlying organic material such as leaf litter, mangrove roots, and submerged driftwood.

Maximum Standard Length

20 – 25 mm.

Aquarium SizeTop ↑

Base dimensions of 45 ∗ 30 cm or equivalent should be the minimum considered.

Maintenance

Provide plenty of hiding places and cover, the idea being to create broken lines of sight to allow weaker individuals to escape continual attention from dominant fish.

Crushed coral or coral sand can be mixed into the substrate to act as a buffer if necessary, or marine salt added at a dose of around 2 grams per litre.

Filtration should not be strong with an air-powered sponge-type unit ideal.

Diet

Small live foods such as Artemia, Daphnia, etc., should be considered essential although some specimens will learn to accept  frozen alternatives. Dried products are normally ignored.

Behaviour and CompatibilityTop ↑

Unlikely to make an ideal community fish and should do best in a species-specific set-up.

Although males in particular are territorial towards one another a group of 6 or more should be the minimum purchase, since when such numbers are present aggression is spread between individuals plus the fish are bolder and exhibit more natural behaviour.

Sexual Dimorphism

Sexually mature females often appear rounder-bodied than males, particularly when gravid.

NotesTop ↑

B. nunus is not particularly common in the international aquarium trade but its  name is widely misapplied to other species such as B. doriae  or B. sabanus which may give a false impression as to its availability.

It actually looks completely different to those two species and can be diagnosed as follows: <30 lateral scales; four black bands on the body; two black body bands reaching ventral midline posterior to anal-fin; a black stripe passing through the eye; presence of at least 7 branched anal-fin rays.

That said, detailed taxonomic work on the genus is long overdue meaning B. nunus and the majority of congeners are best considered nominal taxa for the time being since several other species might be involved.

Although we’ve assigned images of Brachygobius spp. to profiles based on how well they match the key of Inger (1958) their identification can therefore only be thought of as tentative pending publication of a forthcoming review.

Brachygobius currently contains 9 described species, and although all are referred to collectively as ‘bumblebee’ gobies only B. doriae and B. sabanus are commonly-available  in the ornamental trade.

References

1. Hamilton, F. , 1822 - Edinburgh & London: i-vii + 1-405
   An account of the fishes found in the river Ganges and its branches.
2. Dahanukar, N., R. Raut and A. Bhat, 2004 - Journal of Biogeography 31: 123-136
   Distribution, endemism and threat status of freshwater fishes in the Western Ghats of India.
3. Inger, R. F., 1958 - Fieldiana Zoology 39(14): 107-117
   Notes on the fishes of the genus Brachygobius.
4. Miller, P. J., 1989 - Cybium 13(4): 375-383
   The classification of bumble-bee gobies (Brachygobius and associated genera) (Teleostei: Gobiidae).