Rhinogobius lanyuensis CHEN, MILLER & FANG, 1998

Etymology

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

lanyuensis: named for Lanyu Island (aka Orchid Island), to which this species is endemic.

Classification

Order: Perciformes Family: Gobiidae

Distribution

Known only from Lanyu Island, better known as Orchid Island in the English language, located off the southeastern coast of Taiwan and considered part of the Taiwan archipelago itself.

Type locality is given as ‘Dong-Ching brook’ with a second population known from ‘ Ye–Yu brook’.

Habitat

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.

Maximum Standard Length

60 – 67 mm.

Aquarium SizeTop ↑

An aquarium with base dimensions of 80 ∗ 30 cm should be 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: 18 – 25 °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.

Sexual Dimorphism

Males are more intensely-coloured and develop slightly longer dorsal and anal fins than females.

Females possess a discontinuous dark lateral stripe which is lacking in males.

NotesTop ↑

This species may not yet have appeared in the global ornamental trade but it has been available in Japan on occasion.

It can be told apart from congeners by the following combination of characters: 7 spinous dorsal-fin rays; 8 soft dorsal-fin rays; 1 spinous anal-fin ray: 1; 8 soft anal-fin rays; 26 vertebrae; 33-35 scales in the longitudinal series; 13-17 predorsal scales; snout length 32.5-44.5 % and postorbital length 42.5-49.6 % of head length; cheek with orange or brown spots; body with 8 vertical blackish brown bars; second dorsal-fin with several rows of dark spots; pectoral-fin base with 3 vertical dark brown stripes; caudal-fin with several rows of tiny brown spots; female with a discontinuous dark lateral stripe but male without such a stripe.

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., P. J. Miller and L.-S. Fang, 1998 - Ichthyological Exploration of Freshwaters 9(3): 255-261
   A new species of freshwater goby from Lanyu (Orchid Island), Taiwan.
2. Ho, H.-C. and K.-T. Shao, 2011 - Zootaxa 2957: 1-74
   Annotated checklist and type catalog of fish genera and species described from Taiwan.