Lake Eacham Rainbowfish, Melanotaenia eachamensis Allen & Cross 1982

Other Names: Lake Eacham Rainbow Fish

Summary:

A small silvery to bluish rainbowfish with a dark mid-lateral stripe, two fainter ventral bands, and reddish fins. Breeding males may be bronze to orange with a black margin on the dorsal and anal fins, and longer, more pointed and more brightly coloured fins than females.

Cite this page as:

Gomon, M.F. & Bray, D.J. 2025, Melanotaenia eachamensis in Fishes of Australia, accessed 27 Jun 2025, https://fishesofaustralia.net.au/home/species/3640

Lake Eacham Rainbowfish, Melanotaenia eachamensis Allen & Cross 1982

More Info

Distribution	Endemic to the upper reaches of the Barron, North Johnstone and South Johnstone River catchments in Queensland, Australia, at elevations above 460 m; also in Koombooloomba Dam on the Tully River, Atherton Tablelands, Queensland. Individuals form schools amongst aquatic vegetation along the shallow edges of small freshwater creeks and crater lakes.
Features	Dorsal fin V-VI, I, 9-13; Anal fin I, 15-21; Pectoral fin 11-14. Body laterally compressed, relatively elongate; greatest body depth 26.5% of SL; jaws about equal, oblique, premaxilla with an abrupt bend between the anterior horizontal portion and lateral part; jaw reaches back to front of eye; lips thin, except middle portion of upper lip bulbous; teeth conical with slightly curved tips, those in outer row generally stouter; teeth in upper jaw arranged in 2 irregular rows anteriorly, reduced to a single row posteriorly, outer row teeth exposed when mouth is closed; about 70-80 teeth in upper jaw; teeth in lower jaw in 3 or 4 irregular rows anteriorly, tapering to 1 or 2 rows posteriorly; about 140 teeth in lower jaw; vomerine teeth inconspicuous, 4-5 very small conical teeth; palatine with a band of 16-20 teeth arranged in a single row; head length 27.6-32.5 in SL; snout length 7.9-10.0 in SL; eye diameter 8.6-12.1 in SL. Scales large, arranged in regular horizontal rows; body scales with smooth to slightly crenulate margins; horizontal scale rows 10-12; vertical scale rows 33-38; cheek scales 9-15. Two separate dorsal fins; first originates well ahead of anal fin origin; soft dorsal and anal fin rectangular in outline, the posterior rays somewhat elongate and pointed in males. Pelvic fin tips when depressed extending to about base of Ist or 2nd soft anal ray in mature males and not reaching anal fin origin in females; pectoral fins pointed; caudal fin moderately forked.
Size	To around 6.5 cm SL
Colour	Colour varies with locality but generally silvery or bluish to red-brown with dark midlateral stripe and 2-3 thinner dark bands below; fins transparent to bright red; fin margins of breeding males black.
Feeding	Feeds on aquatic and terrestrial invertebrates, and algae.
Biology	Spawning occurs from August to April with peak activity from August to November. Eggs are attached to fine root masses in well oxygenated areas. Eggs are small, demersal and adhesive. Larvae are small at hatching and lack a well-developed yolk sac. Larval development is complete at 11-14 mm TL.
Fisheries
Conservation	The species is threatened by hybridisation with other rainbowfish that are expanding their range into Eacham Rainbowfish habitat along with expansion of exotic fishes like Gambusia and various Tilapias. Habitat degradation (siltation from grazing and sugar cane farming; changes to channel morphology by removal of riparian vegetation; and invasive weeds) also a major threat. A previous attempt to re-introduce 300 fish into Lake Eacham failed as invasive predatory fish were not removed from the lake before the release. Eastern Rainbowfish is now established in the Lake.
Remarks	Although thought to be extinct in 1987, the Lake Eacham Rainbowfish was rediscovered in the private collections of aquarists. The species was subsequently found to have a wider distribution, with populations surviving in the wild in the Upper Barron and Johnstone River catchments. Although locally common with a very patchy distribution, ongoing introgression with the Eastern Rainbowfish, Melanotaenia splendida, has resulted in an observed decline in mature individuals.
Etymology	The species is named eachamensis after the type locality, Lake Eacham.
Species Citation	Melanotaenia eachamensis Allen & Cross, 1982, Rainbowfishes of Australia and Papua New Guinea: 45. Type locality: Lake Eacham, Atherton Tableland, N QLD.
Author	Gomon, M.F. & Bray, D.J. 2025
Resources	Atlas of Living Australia Australian Faunal Directory Catalog of Fishes

Lake Eacham Rainbowfish, Melanotaenia eachamensis Allen & Cross 1982

References

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