Melanotaenia fluviatilis
(Australian rainbowfish)
Fishes
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Common name: Australian rainbowfish
Synonyms and Other Names: Crimson-spotted rainbowfish
Taxonomy: available through
www.itis.gov
Identification: Shape and color vary with age, maturity, and sex of this species (Backhouse and Frusher 1980). The body becomes deeper with age while the dorsal profile of the head becomes more concave; the lower jaw often protrudes in mature fish (Backhouse and Frusher 1980). Melanotaenia fluviatilis have two dorsal fins separated by a small gap and a prominent red spot on the operculum (Munro 1980). The body is silvery with green iridescence, darker dorsally and lighter to almost white ventrally (Backhouse and Frusher 1980). This species is sexually dimorphic with the females being smaller and less colorful while the males are more brightly colored and have longer first dorsal spines and second dorsal rays (Munro 1980). Prior to spawning the male’s body becomes green, with an orange throat, and red caudal fin with the remaining fins becoming yellow flecked with orange and intense black margins (Munro 1980, Merrick and Schmida 1984).
Size: Males reach a maximum size of 90 mm SL, but usually less than 70 mm with females to about 75 mm SL (Allen and Cross 1982).
Native Range: Native to Australia in the coastal section of southern Queensland and also inland from New South Wales, Victoria, and South Australia (Allen and Cross 1982).
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Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps
Nonindigenous Occurrences:
Ecology: Melanotaenia fluviatilis is typically found in clear water streams, lakes, and reservoirs with minimal flow, submerged vegetation, and sunlit areas (Allen and Cross 1982). This species is a surface feeder with a diet consisting primarily of insects and small crustaceans, but also filamentous algae (Backhouse and Frusher 1980, Munro 1980). This species is adapted to low winter temperatures of 10-15°C (Allen et al. 2002), but spawns in warmer temperatures (20-25°C) in the spring and early summer (Munro 1980). Males perform an elaborate spawning courtship display and pairing only lasts for a single spawning event (Merrick and Schmida 1984). Females release up to 10 eggs per spawning event and will spawn 3-4 times per day for several days (Merrick and Schmida 1984). The eggs attach to vegetation with a small thread and develop in 6-7 days (Munro 1980). The larvae hang on to the vegetation for two days before becoming free swimming (Munro 1980).
Means of Introduction: Escaped aquaculture
Status: unknown
Impact of Introduction: The impacts of this species are currently unknown, as no studies have been done to determine how it has affected ecosystems in the invaded range. The absence of data does not equate to lack of effects. It does, however, mean that research is required to evaluate effects before conclusions can be made.
References: (click for full references)
Allen, G.R, and N.J. Cross. 1982. Rainbowfishes of Australia and Papua New Guinea. T.F.H. Publications Inc., Australia.
Allen, G.R., S.H. Midgley, and M. Allen. 2002. Field guide to the freshwater fishes of Australia. Quality Press, Perth, Australia.
Backhouse, G.N., and D.J. Frusher. 1980. The crimson-spotted rainbowfish, Melanotaenia fluviatilis (Castelnau 1878). The Victorian Naturalist 97:144-148.
Merrick, J.R., and G.E. Schmida. 1984. Australian freshwater fishes. Griffin Press Ltd, South Australia, Australia.
Munro, I.S.R. 1980. Family Melanotaeniidae: Rainbowfishes. Pages 129-131 in McDowell, R.M. ed. Freshwater Fishes of South-Eastern Australia. Reed Ltd, Sydney, Australia.
Author:
Brown, M.E.
Revision Date: 3/4/2025
Citation Information:
U.S. Geological Survey, 2026, Melanotaenia fluviatilis (Castelnau, 1878): Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=3856, Revision Date: 3/4/2025, Access Date: 6/13/2026
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.
