Rhinogobius duospilus

Rhinogobius: from the Greek rhinos, meaning 'nose', and the generic name Gobius.

duospilus: from the Latin duo, meaning 'two', and the Greek spilos, meaning 'spot' or 'mark', in reference to the two prominent spots at the base of the pectoral fin.

Described from Hong Kong and known from much of southern China, including Shenzhen in Guangdong province immediately north of the type locality.

Type locality is given as 'Brook in hills of the New Territory, Hong Kong'.

FishBase and Kottelat (2001) also list it from northern Vietnam, but we've been unable to confirm those records, and several similar-looking species occur there.

Records from Guangxi province should also be treated with caution, since R. wui, described from the Yaoshan mountains in Guangxi, was treated as a synonym of this species until recently (see 'Notes').

A bottom-dwelling fish of small, clear hill streams, where it clings to rocks with the sucker-like disc formed by its pelvic fins.

In Hong Kong these streams are a series of riffles and pools over beds of stones and boulders, and the water is often slightly acidic, nutrient-poor and of low conductivity (Yang and Dudgeon, 2010).

It occurs there alongside the loaches Pseudogastromyzon myersi, Liniparhomaloptera disparis and Schistura fasciolata, and a congener, R. similis, is also found in the territory.

Adults are extremely sedentary. In a marking study in a Hong Kong hill stream the fish had moved an average of about 3 m after 35 weeks (Ho and Dudgeon, 2016), and populations in neighbouring streams are genetically distinct from one another (Chan et al., 2026).

An aquarium with base dimensions of 60 ∗ 30 cm24 ∗ 12 in is large enough to house a small group.

Not difficult to maintain under the correct conditions; we strongly recommend keeping it in a tank designed to simulate a flowing stream with a substrate of variably-sized rocks, sand, fine gravel, and some water-worn boulders.

This can be further furnished with driftwood branches, terracotta pipes, plant pots, etc., arranged to form a network of nooks, crannies, and shaded spots, thus providing broken lines of sight.

While the majority of aquatic plants will fail to thrive in such surroundings hardy types such as Microsorum, Bolbitis, or Anubias spp. can be grown attached to the décor.

Like many fishes that naturally inhabit running water it's intolerant to accumulation of organic pollutants and requires spotless water in order to thrive, thus weekly water changes of 30-50% tank volume should also be considered routine.

Though torrent-like conditions are unnecessary it does best if there is a high proportion of dissolved oxygen and some water movement in the tank meaning power filter(s), additional powerhead(s), or airstone(s) should be employed as necessary.

In nature it feeds on small invertebrates.

In the aquarium they should be offered small live or frozen foods such as chironomid (bloodworm) or mosquito larvae, Artemia, Daphnia, Mysis, etc.

Dried foods may be accepted following a period of acclimatisation but should not be used regularly.

Best kept in a species tank, or with small, peaceful fishes that stay in the upper part of the water column, such as Tanichthys or Microdevario spp.

Freshwater shrimp such as Caridina and Neocaridina spp. are likely to be eaten and are best avoided.

It should not be mixed with other Rhinogobius spp., since it's not yet clear whether they can hybridise.

Males are territorial with one another, but serious damage is unlikely provided the tank contains enough cover, and the fish appear to need the company of their own kind.

Aim to buy at least two males and as many or more females, or the fish may become listless and inactive.

Mature males are more colourful than females, particularly when in breeding condition (Wu et al., 2025). As in congeners, males also tend to grow larger and develop longer unpaired fins.

Unlike amphidromous congeners, whose larvae drift down to the sea, R. duospilus spends its whole life in fresh water, and the young develop directly into juveniles soon after hatching (Chan et al., 2026).

As is typical for the genus, the eggs are laid on the underside of a stone or in a crevice and guarded by the male until they hatch, so flat stones, slate or clay pipes should be provided.

Members of the R. duospilus group have been bred in aquaria, but because these fish are so hard to identify it isn't known which species were involved. We have no reliable figures for clutch size or incubation period in this species.

This species is traded as the 'white-cheeked goby', and in the past was often sold as 'Rhinogobius wui'.

R. wui (Liu, 1940), described from Guangxi province, was treated as a synonym of R. duospilus from 1991 until Endruweit (2024) designated a neotype for it, and the Catalog of Fishes now lists it as a valid species. Aquarium literature published under either name may therefore refer to either fish.

Endruweit (2024) also placed R. duospilus in a new genus, Zhuquella, together with around 20 similar species from southern China and Vietnam. This has not yet been widely followed, and we retain it in Rhinogobius pending further study.

Ctenogobius whitleyi Herre, 1936, described from Sha Tin in Hong Kong, is a synonym.

FishBase gives the following counts: second dorsal-fin I, 8-9; anal-fin I, 6-7; longitudinal scale series 30-32; vertebrae 27.

Hong Kong populations are genetically distinct from one stream system to the next, and the population on Lantau Island has been suggested to represent an undescribed species (Chan et al., 2026).

The Gobiidae is the most speciose vertebrate family and notoriously problematic in terms of identifying fishes down to species level.

Within this sizeable assemblage Rhinogobius is often included in the subfamily Gobionellinae alongside genera such as Brachygobius, Chlamydogobius, Mugilogobius, Pseudogobiopsis, Schismatogobius, and Stigmatogobius.

Members can be told apart from these and all other gobiid genera by the following combination of characters: head with four simple, longitudinal infraorbital sensory papilla rows a, b, c, and d, single cp papilla, and paired papillae in mental row f; head canal variable from complete loss to normal development of anterior and posterior oculoscapular canals, and preopercular canals, and always with double interorbital pores λ if the pore is present; body mostly covered with ctenoid scales; longitudinal scale series 25–42; head including cheek, snout, opercle, anterior part of nape as well as pre-pectoral region all naked; D1 usually VI; D2 I, 6–11; A I, 5–11; P 14–23; and V I, 5 + I, 5, forming a rounded disc with frenum present, performing two pointed spinous lobes, the spinous ray usually longer than the first branched ray; dorsal pterygiophore formulae modally 3–22 1 101; vertebrae 25–29, usually 26 for most landlocked species.

The genus is widely-distributed throughout much of continental Asia in Russia, Korea, China, Vietnam, Laos, Cambodia, and Thailand, plus numerous islands of the Western Pacific including Japan, Taiwan, Hainan, and the Philippines.

There currently exist over 60 recognised species with many more awaiting formal description, and a number of the described ones are only considered nominal taxa pending additional study.

Those exhibiting similarities in appearance, morphology and behaviour are therefore often aggregated in nominal species groups, e.g., the R. brunneus group, R. duospilus group, etc., for ease of reference.

The fused pelvic fins form a structure normally referred to as the 'pelvic disc', a common feature among gobiids which is used to adhere to rocks and other submerged surfaces.

Rhinogobius spp. also exhibit different reproductive strategies depending on environment, with those inhabiting rivers connected directly to the sea typically amphidromous, and those landlocked in upper reaches of rivers or lakes non-diadromous.

Many of those appearing in the aquarium trade have proven difficult to identify for a number of reasons including:

- taxonomic confusion.
- lack of aquarium literature.
- incorrect labelling by exporters and subsequently shops.
- historical over-use of some names, e.g., 'Rhinogobius wui', which was long treated as a synonym of R. duospilus and is now considered valid.
- likely trade of undescribed species without locality data.
- mixing of species at export facilities.