Taxonomy & naming
Gobiomorphus australis was originally described by the German-Australian naturalist Gerard Krefft in 1864 under the combination Eleotris australis, placing it in the broad eleotrid catch-all genus of the era. The valid genus Gobiomorphus was established later, and the Catalog of Fishes — the international authority for valid fish names — now places this species as Gobiomorphus australis (Krefft, 1864), with the original author's name in parentheses to signal the transfer. The family is Eleotridae, the sleepers and gudgeons.
This is not a true goby. True gobies (families Gobiidae, Gobionellidae, Oxudercidae) share the diagnostic character of pelvic fins that are united into a concave sucker disc; in the eleotrids the pelvic fins stay free and separate. Gobiomorphus australis is therefore more accurately called the striped gudgeon than a goby at all, though both names appear in Australian freshwater literature. The genus Gobiomorphus contains around thirteen species, all restricted to Australia and New Zealand, and G. australis is the sole species in the southern Australian drainages where it occurs.
Morphology
The striped gudgeon is an elongate, moderately robust sleeper. Maximum recorded total length is 7 in, but the typical adult runs closer to 4.5 in. The body is patterned with a series of dark lateral blotches or stripes along a paler ground colour, giving the fish the common name; the fins are generally clear to dusky. Two dorsal fins are present, as in all eleotrids — the first short and spiny, the second soft-rayed and longer — and the free, separate pelvic fins distinguish it at a glance from any true goby that might share the same drainage.
Sexual dimorphism is modest but present: mature males tend to be slightly larger and develop more vivid colouration and extended fin rays during the breeding season. Females in breeding condition are fuller-bodied. Outside the spawning period the sexes can be difficult to separate in the field.
Habitat
Gobiomorphus australis is endemic to eastern Australia, occurring from approximately the Pioneer River near Mackay in Queensland (around 21°S) south to South Gippsland, Victoria (around 38°S), with the distribution becoming patchy north of the Mary River. It occupies an unusually broad range of freshwater habitats: clear, fast-flowing rocky streams as well as slow, muddy lagoons, ponds and waterholes. Juveniles returning from the sea are regularly found in estuaries, among rocks, logs and aquatic vegetation in the tidal zone, and the species is a capable climber, scaling wet rocks and negotiating rapids to reach upstream habitats.
Water temperatures across its range span roughly 64–77 °F, and spawning takes place at around 70 °F in late austral summer to early autumn. Adults are primarily freshwater fish; the estuarine connection belongs to the larval and early juvenile stages of the amphidromous life cycle rather than to the adults themselves.
Feeding
The striped gudgeon is a micro-predator with a trophic level of approximately 3.7, consistent with a diet centred on animal prey. In the wild it takes aquatic insects and their larvae, small crustaceans and — at larger sizes — small fishes. It is an opportunistic sit-and-wait or short-burst predator rather than an open-water pursuer.
In the aquarium it does best on live and frozen meaty foods: bloodworm, brine shrimp, daphnia, small crustaceans and similar invertebrate fare sized to its gape. Many individuals will accept good-quality sinking pellets and frozen prepared foods over time, but a diet based solely on dry flake rarely keeps the fish in peak condition. Because it can reach a respectable 4.5–7 in, it will eventually take small feeder invertebrates and could prey on very small tank mates.
Mating
Gobiomorphus australis is an amphidromous species. Spawning takes place in fresh water, typically in late austral summer or early autumn when water temperatures reach around 70 °F. Males compete for and hold spawning territories that include a suitable hard substrate — a rock face, the underside of a submerged log or a crevice — where the eggs will be laid. Courtship involves the male displaying to and guiding a ripe female toward the chosen site.
Once the female is in position she deposits a compact, single-layer clutch of adhesive eggs directly onto the rock or log surface. The male then takes sole responsibility for guarding and tending the eggs, while the female departs. This type of substrate-attached, male-guarded clutch is typical of Gobiomorphus and of amphidromous eleotrids generally.
Breeding
After spawning, the male striped gudgeon guards the egg clutch, fanning it with his fins to maintain water movement and oxygenation. Incubation is short — approximately four days at typical spawning temperatures. When the eggs hatch, the newly-emergent larvae are carried downstream by river current within hours of hatching and enter estuarine and coastal marine waters, where they develop as part of the plankton community. The marine larval phase can last weeks to months. Post-larvae eventually return to freshwater as small juveniles, often climbing over wet rocky obstructions to reach upstream habitats.
Because the larvae must complete development in the sea, Gobiomorphus australis cannot complete its breeding cycle in any closed freshwater aquarium system and is effectively impossible to breed in captivity. Fish in the trade are wild-collected. Hobbyists who acquire this species should understand that the population in captivity cannot be replenished through home breeding, and that individual fish may be stressed by the journey from the wild.
In the aquarium
The striped gudgeon is a rewarding but somewhat demanding species for the experienced keeper of Australian natives. A tank of at least 25 US gal is appropriate for a single specimen or pair; the species can reach 7 in and is active in the lower and mid-water column. Moderate water flow, good filtration, and a decor of rounded rocks, submerged logs and robust plants will replicate the stream and lagoon conditions it inhabits. A securely fitted lid is advisable — like many eleotrids it is a capable jumper.
Water temperature in the 64–77 °F range suits it, and as a temperate to warm-temperate Australian species it does not need the tropical temperatures appropriate for Southeast Asian or equatorial fish; keeping it too warm can shorten its lifespan. Diet should be based on live and frozen foods (bloodworm, brine shrimp, small crustaceans), supplemented with sinking pellets once accepted. It can be kept with robust fish of similar or larger size, but will prey on anything that fits its mouth. Longevity in a well-run aquarium is reportedly five to eight years. Because it is amphidromous and cannot be bred in captivity, all specimens are wild-collected; buy from reputable Australian native fish dealers and avoid specimens that appear exhausted or refuse food for extended periods.
Conservation
Gobiomorphus australis is assessed as Least Concern on the IUCN Red List (2019 assessment, assessed 15 February 2019). Its range across eastern Australian drainages is reasonably broad, and while the distribution is patchy in the northern part of the range (north of the Mary River), populations in Queensland, New South Wales and Victoria are generally considered stable under current conditions.
The species' amphidromous life history means that it depends on intact connectivity between freshwater spawning habitat and the coastal marine environment where larvae develop. Barriers such as dams, weirs and causeways that prevent larval drift downstream or post-larval migration upstream pose the primary structural threat to its persistence in any given catchment. Degradation of riparian and in-stream habitat, changed hydrology from water extraction, and agricultural run-off affecting water quality are secondary pressures across its range. Because it cannot be bred in captivity, the aquarium trade relies entirely on wild collection; responsible sourcing and cautious stocking numbers are appropriate.