Rhinogobius yaoshanensis (LUO, 1989)

SynonymsTop ↑

Ctenogobius yaoshanensis Luo, 1989

Etymology

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

yaoshanensis: we haven’t seen the original description but presumably named for Da Yao Shan mountain which lies close to the type locality given for the species (see ‘Distribution).

Classification

Order: Perciformes Family: Gobiidae

Distribution

Type locality is given as ‘Jinxiu, Guangxi, China’, which corresponds to Jinxiu Yao Autonomous County of Laibin City in eastern Guangxi Zhuang Autonomous Region.

Jinxiu Yao is mostly mountainous and prior to 1966 was known as Dayaoshan Autonomous Zone in reference to nearby Da Yao Shan (Da Yao Mountain).

R. yaoshanensis only appears to have been recorded from streams draining this area to date.

Habitat

Likely restricted to shallow, flowing, well-oxygenated headwaters and minor tributaries characterised by stretches of riffles and runs broken up by pools or cascades in some cases.

Substrates in such habitats are normally composed of smaller rocks, sand and gravel with jumbles of boulders and patches of submerged leaf litter.

During periods of high rainfall some streams may be temporarily turbid due to suspended material dislodged by increased, sometimes torrential, flow rate and water depth.

Maximum Standard Length

At least 45 mm.

Aquarium SizeTop ↑

An aquarium with base dimensions of 60 ∗ 30 cm should prove large enough to house a small group.

Maintenance

Should not prove difficult to maintain under the correct conditions; as per other Rhinogobius spp. 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.

Water Conditions

Temperature: 16 – 24 °C

pH: 6.0 – 8.0

Hardness: 36 – 268 ppm

Diet

Rhinogobius spp. tend to be opportunistic carnivores feeding on a range of small invertebrates, crustaceans and similar in nature.

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.

NotesTop ↑

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 in which it’s included (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 caught close to the type locality.

Chen et al. (2008) suggest that R. yaoshanensis can be told apart from congeners by possession of 5-8 scales between the origins of the first dorsal-fin and upper pectoral-fin, 14-15 predorsal scales, small cycloid scales in the pre-pelvic region, postorbital region with paired pore ω and preopercular region with 3 pores.

This gives the fish a somewhat flattish, elongate profile despite its small size since the majority of related congeners have 9-11 scales between the origins of the first dorsal-fin and upper pectoral-fin plus 0-11 predorsal scales.

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 is itself an invalid synonym of R. duospilus.
– likely trade of undescribed species without locality data.
– mixing of species at export facilities.

References

1. Chen, I-S., Y.-H. Cheng and K.-T. Shao, 2008 - Ichthyological Research 55(4): 335-343
   A new species of Rhinogobius (Teleostei: Gobiidae) from the Julongjiang basin in Fujian Province, China.