- Last updated:
- 12 Sep 2022
Article by Daniel Bloom, Waterways Project Officer, Sunshine Coast Council
The three species of fish observed on the video below are the Australian smelt (Retropinna semoni), the southern purple-spotted gudgeon (Mogurnda adspersa) and the crimson-spotted rainbowfish (Melanotaenia duboulayi). Each of these fish species are common and abundant in south-east Queensland. Previous surveys indicate that they are more abundant in the Mary, Brisbane, Logan and Albert catchments rather than the short coastal catchments of the Moreton and Sunshine Coast regions (Pusey et al., 2004).
These fish species all move and complete their lifecycles within freshwater, however Australian smelt may transition from brackish areas in estuaries right up into the headwaters of streams sometimes in the thousands (Hansen, 1989; Midgley & Allen, 2002). While widespread and common, the main threats to these species include degradation and loss of habitat, barriers to movement, water regulation and predation from non-native and non-endemic species (Arthington et al., 1983). Below are a few basic and interesting facts about these local freshwater species.
Australian smelt (Retropinna semoni)
The Australian smelt is a small pelagic fish species commonly observed at 50-60mm long but they are known to reach 100mm and live as long as three years or more (McDowall, 1996).
Australian smelt occur from Baffle Creek south to the mouth of the Murray River including Fraser and Moreton Islands and are found within the Murray darling and Lake Eyre basins (Allen et al., 2002; McDowall, 1996).
Australian smelt appear to be tolerant of a wide range of water quality and habitat conditions from excellent to poor, however they have been noted to be intolerant of prolonged exposure to high levels of suspended sediment (Cadwaller & Backhouse, 1983). The peak spawning time in south-eastern Queensland is between winter and early spring, usually coinciding with periods of low and stable river flows and prior to flooding. However, spawning can occur well into late summer in a variety of flow conditions (Milton & Arthington 1985; Pusey et al., 2004). These fish feed mainly on small larval flies, mayflies, caddisflies and micro-crustaceans (Arthington, 1992).
Southern purple-spotted gudgeon (Mogurnda adspersa)
The southern purple-spotted gudgeon is thought to grow to 140mm in length (Allen et al., 2002; Larson & Hoese, 1996). This species is widespread and has a considerable genetic diversity between drainage basins within its range from Cape York to the Clarence River in New South Wales and west into the Murray Darling Basin (Allen & Jenkins, 1999; Morris et al. 2000).
This species prefers slow flowing pools and billabongs from the upper reaches of estuaries up into the headwaters of streams and is almost always found around cover such as root systems, undercut banks and amongst instream vegetation (Cadwallader & Backhouse, 1983). South-east Queensland populations of purple-spotted gudgeon tend to concentrate their spawning in spring and summer (mainly Nov-Feb), a few months later than their northern neighbours in the wet tropics. Females are repeat spawners that may produce up to 1300 eggs per spawning season depending on location (Pusey et al. 2004; Llewellyn, 2006). Eggs are laid in clusters attached to rocks or vegetation where the male may actively guard and fans the eggs until they hatch (Tappin, 1997 cited in Pusey et al. 2004; Llewellyn 2006).
There is some speculation that this species may be excellent at negotiating barriers such as waterfalls but more research is needed to confirm this. (Pusey & Kennard, 1996; Pusey et al. 2004). The main prey item of this fish species is aquatic and terrestrial insects, aquatic crustaceans and occasionally molluscs and other small fish. In the coastal drainage basins this species is relatively common, however in the southern extent of its range it is listed as critically endangered in South Australia, where it was once thought to be extinct. It is listed as endangered in New South Wales and threatened and regionally extinct in Victoria (Gomon & Bray, 2018).
Crimson-spotted rainbowfish (Melanotaenia duboulayi)
The Crimson-spotted rainbowfish grows to 90mm in the wild and commonly occurs in coastal drainages from Baffle Creek in central Queensland to Hastings River in northern New South Wales. Currently this species is a popular aquarium fish and interestingly, was one of the first fish species to be kept in captivity and exported to Germany and the United States in the 1920s and 30s. As a result ’wild’ populations have established in the United States (Pusey et el. 2004; Allen 1996). The spawning season for this species is extended throughout the year but commences in late winter and is concentrated in spring and summer (Pusey et el. 2004). The omnivorous diet of this rainbowfish species consists mainly of terrestrial insects (mostly ants) followed but aquatic insects and vegetation (Arthington, 1992; Pusey et al. 2004).
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- Allen, G.R. & A.P. Jenkins (1999). A review of the Australian freshwater gudgeons, genus Mogurnda (Eleotridae) with descriptions of three new species. Journal of Icthyology and Aquatic Biology 3: 141-156.
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- Tappin, A.R. (1997). Morgunda adspersa – The purple spotted Gudgeon. Australian New Guinea Fishes Association Bulletin 32, 1-3.