Taxonomy & naming
Mugilogobius chulae was described by the American ichthyologist Hugh McCormick Smith in 1932 from a type locality of Koh Samui — Samui Island in the Gulf of Thailand — where it was taken from a brackish coastal pool. The Catalog of Fishes (Eschmeyer, CAS), the authority for valid names, places it in the genus Mugilogobius within the family Oxudercidae. The Gobioidei have been reshuffled repeatedly as molecular phylogenetics has teased apart the traditional Gobiidae sensu lato; the family Oxudercidae as currently recognised includes the mudskippers and a broad assemblage of Indo-Pacific freshwater and brackish gobies.
This is a true goby, not a sleeper or gudgeon: the defining character is the pelvic fins, which are fused into a cup-shaped sucker disc used to anchor the fish on hard surfaces and in current. Sleepers and gudgeons (family Eleotridae) keep their pelvic fins separate, and that single feature divides the two groups cleanly. Although gobies are an overwhelmingly marine group — with more than 2,000 species, the largest vertebrate family on earth by many counts — Mugilogobius chulae has pushed into fresh and brackish water and is the exception rather than the rule.
Older literature may place this species under Gobius, Vaimosa or related catch-all genera that were used before the modern revision; the current combination Mugilogobius chulae (Smith, 1932) is the valid one. The species name honours Luang Chula Cachanagupta, Director of the Department of Fisheries of Siam (Thailand) at the time of the description.
Morphology
Mugilogobius chulae is a slender, small-bodied goby that reaches a maximum of 1.5 in total length in both the wild and the aquarium. The body is typical of the Mugilogobius build — somewhat cylindrical and tapering, with two separate dorsal fins, a blunt head and the broad-based pectoral fins common to benthic gobies. The fused pelvic fins form the sucker disc that gobies use to cling to stones and substrate in current.
Males are brighter in colour than females and develop longer, more extended fins, typically reaching 1.5 in; females tend to be slightly smaller and plainer. A pale yellowish stripe runs along the flank, giving the fish its vernacular name. The overall colouration is muted — sandy to olive above, paler below — as befits a fish that lives among substrate and debris in turbid estuarine water, and the markings provide effective camouflage against a sandy or muddy bottom.
Habitat
Mugilogobius chulae occupies tidal river reaches, estuaries, coastal pools and the lower portions of streams where fresh and salt water mix — an essentially brackish zone that shifts with the tides, seasonal floods and proximity to the sea. FishBase records a preferred temperature range of roughly 77–84 °F (mean 82 °F), consistent with a tropical estuarine species. Water hardness is typically moderate to high and pH above 7, reflecting the influence of seawater.
The native range spans the western Pacific and eastern Indian Ocean: Thailand and the Gulf of Thailand (the type locality), Sumatra, the Philippines, Taiwan and the Ryukyu Islands of southern Japan. It tends to use the very lowest reaches of watercourses and does not penetrate far inland; its affinity for tidal influence is strong. The species is recorded from shallow, gently flowing to still coastal habitats rather than fast upland streams.
Feeding
Mugilogobius chulae is a micro-predator, foraging along the bottom for small crustaceans, aquatic insect larvae and other small invertebrates — the typical diet of a small benthic goby that hunts by sight in the shallows. It does not graze algae in the manner of the cling-gobies (Stiphodon, Sicyopterus), nor is it a filter-feeder; it selects individual prey items from the substrate and water column.
In the aquarium the species should be offered a varied diet of small live and frozen foods: bloodworm (chironomid larvae), brine shrimp, daphnia, cyclops and other small crustaceans and insect larvae. It typically refuses or ignores standard dry flake food, and a fish maintained solely on flake loses condition quickly. Regular offerings of live or frozen invertebrates are essential for long-term health and colour.
Mating
Mugilogobius chulae is an amphidromous goby: adults breed in brackish estuarine water, but the resulting larvae are swept downstream and out to sea, where they develop in the marine plankton before the post-larvae return to coastal fresh and brackish habitats to grow to maturity. This diadromous life history is shared by many coastal gobies and is the reason the species cannot be considered a candidate for straightforward aquarium breeding.
In the wild, males presumably defend territories and court females at spawning sites on hard substrate in the tidal zone, consistent with what is known of other small Mugilogobius species. The fused pelvic sucker disc is relevant here: it allows the fish to maintain position against tidal current while attending to spawning activities. However, the critical point for the aquarist is that any eggs produced would hatch larvae that require a marine larval phase — something a home aquarium cannot replicate.
Breeding
Because Mugilogobius chulae is amphidromous, breeding it in captivity is not a realistic prospect. The larvae that hatch from any spawning must develop in the open sea as marine plankton — a phase that cannot be reproduced in a home aquarium or even most public aquarium facilities. This contrasts sharply with the resident cave-spawning gobies (such as Rhinogobius or Brachygobius species) that complete their entire life cycle in fresh or brackish water and can be bred routinely.
All specimens available in the trade are therefore wild-collected, and buyers should be aware of this. The collection of wild fish from estuarine habitats is generally low-impact when conducted carefully and at sustainable levels, but it does mean that any individual lost cannot be replaced from captive stock. There are no reports in the aquarium literature of successful captive propagation of this species.
In the aquarium
Mugilogobius chulae is a specialist fish for the brackish aquarium. It requires a low to moderate salinity — hobbyist sources recommend around 3–5 g of marine salt per litre as a starting point — along with hard, alkaline water (pH above 7.5, ideally above 8) and warm temperatures in the 77–84 °F range. A standard freshwater community tank without salt is not appropriate; kept long-term in plain fresh water the fish declines.
The tank should offer a sandy or fine-gravel substrate, low to moderate flow, and plenty of shelter in the form of rocks, caves, flowerpots and driftwood. Males can be territorial with one another, so multiple hiding spots that break lines of sight are important if more than one male is kept. As a small goby (1.5 in maximum) it suits a nano or species-only brackish setup rather than a large community tank; potential tankmates should be robust enough to tolerate brackish conditions. The main practical challenges are feeding — the fish needs live or frozen invertebrates and rarely accepts flake — and the fact that all specimens are wild-caught, so sourcing can be difficult. It is rare in the trade and mainly encountered through specialist brackish-fish dealers.
Conservation
Mugilogobius chulae is assessed as Least Concern on the IUCN Red List (2020 assessment). Its distribution across several countries and island groups in the western Pacific, combined with its use of widespread estuarine and tidal habitats, supports this relatively secure status. The species is not known to face acute collection pressure despite being wild-caught for the hobby, as demand is low and collection volumes are small.
The long-term risks to estuarine gobies of this type are the familiar threats of coastal development, mangrove clearance, pollution of tidal zones and the alteration of river mouths by water extraction and flood management — pressures that affect biodiversity across the western Pacific coastal zone broadly. There are no species-specific conservation programmes, and no captive breeding safety-net population exists. The reliance on wild collection for the hobby, while currently low in scale, underlines the importance of maintaining healthy estuarine habitats across the species' range.