Known from various parts of the middle and upper Mekong river basins with record existing from the Nam Tha, Nam Ou, Nam Khan, Nam Lik, Nam Ngum and Nam Mang tributary systems in Laos, the Nam Noeua (a tributary of Nam Ou) in Vietnam, and the Mae Nam Kok in Thailand.

Occurrences in the Chao Phraya drainage in central Thailand most likely refer to the congener R. chiengmaiensis.

This species has been exported for the ornamental trade but often labelled as the congener R. mekongianus.

Although the two do appear relatively similar R. chiengmaiensis can be identified by a combination of external characters including: presence of 5 irregular dark markings on the body (vs. 7-8 i…

This species’ name has appeared quite regularly on ornamental fish trade lists since the mid-00’s but it’s unclear whether the species itself has ever been exported since fish labelled as such do not appear to fully match the most recent key (see below).

That said, its natural habitats lie in the same region as the loach Yaoshania pachychilus so it’s reasonable to assume that some specimens may have been collected, and the fish in our images were ca…

This species was previously considered to be a subspecies of R. nagoyae but has generally been accepted as distinct since 2008.

It can be told apart from other Rhinogobius spp. from Taiwan by presence of irregular, wavy, reddish brown lines on the cheek and opercle.

This species may not yet have appeared in the ornamental trade but it has been collected by a few individuals.

It can be told apart from related species from Taiwan by possessing 30-32 longitudinal (lateral) scales vs. 32-39 in other species, and 6-8 scale rows between the origin of the first dorsal-fin and upper pectoral-fin base vs. 9-15 in other species.

It’s unlikely that this species has been in the aquarium hobby given its natural range and the lack of commercial fishing for the ornamental trade in that area.

Among congeners it’s most similar to R. davidi but can be told apart by presence of 8 (vs. always 9 in R. davidi) soft dorsal-fin rays, 10 (vs. 11-12) transverse scale rows, and 6-7 (vs. 8-10) scales between the first dorsal-fin origin and upper pectoral-fin base.

This species appears to exist in a number of different forms which exhibit differences in colour pattern, morphology, or both, and it’s currently unclear whether all of them are truly conspecific or not although those in the aquarium trade all appear similar to one another.

We’ve been unable to obtain a copy of the original description so it’s not currently possible to provide a detailed diagnosis either, with most recent studi…

Presumably inhabits small rivers, tributaries and streams with substrates of gravel, rocks, boulders, and exposed bedrock which undergo seasonal variations in water flow rate, depth and turbidity.

Lanyu Island is volcanic, measures just 45 km² and has no major rivers or large settlements with a permanent human population of around 4000, although there is a large nuclear waste storage facility at its southern end.

In addition, there appear to exist two colour forms based on male dorsal-fin morphology and patterning; one in which the 4th ray of the first dorsal-fin is longest with a square bluish-black blotch on the anterior ⅔ of the fin, and a second in which the 2nd and 3rd rays of the first dorsal-fin are longest with the fin itself paler and lacking dark markings.

Very few details exist but the type locality is given as ‘Yangso, Li Kiang, Kwangsi Province, southern China’, which should correspond to an unspecified location within the Li River (Li Jiang) system in Guangxi Zhuang Autonomous Region, southern China.

The specimens in our images were collected i…