Southern Smelt Retropinna semoni
Australian Smelt is a small, compressed, moderately deep – bodied fish with large eyes and a somewhat rounded snout. Dorsal fin small and high well back on trunk originating just a little in front of level of anal fin; anal fin longer than lower with rays towards rear much shorter.
Scales present on trunk but absent from head. No lateral line though there is often a mid-lateral pigment row that looks like a lateral line.
Australian Smelt is one of the most widespread species in Australia’s south east. The Australian smelt occurs in costal drainages from about the Fitzroy River in southern Queensland, south and west as far as eastern south Australia; also, in tributaries of the Murray – Darling system that join the south-east though not those joining from the north-west; however, it occurs in cooper creek drainages that flow towards or into lake Eyre.
Australian smelt were introduced into Tasmania during the 1960s but success was elusive; the species persisted only in a farm dam and was never released into wild habitats.
Sexual Dimorphism (Differences)
Differences between sexes develop as fish approach sexual maturity. The fins of males become greatly enlarged and quite spectacular, especially in populations where maturity is reached at a small size, pectoral and pelvic fins being particularly enlarged. Small horny nodules (Nuptial tubercles) develop on scales and fin rays in both sexes though they are more abundant and widespread in males than in females.
Colours are bright silvery, back and upper sides somewhat olive, a little darker than lower sides and belly; belly silvery white, eyes silvery; top of head and snout often dusky and fins largely unpigmented.
The size of the smelt varies, this is a tiny species that may reach 100mm, but rarely exceed 75mm and in most populations reaches only 50-60mm. Size reached less in northern than in southern populations, while those in inland drainages particularly may reach maturity at only 40mm.<
Australian smelt occur in still and gently flowing waters of south- eastern Australia in great abundance, often as large roving shoals of small fish. Though other species of retropinnid spend part of their lives at sea (being anadromous), this is certainly not an obligatory aspect of the life cycle and may not occur at all.
In both sexes, only the left gonad is present. They reach maturity towards the end of their first year and may live for two or more years. Spawning takes place when water temperature reaches about 15oC and occurs from mid-winter to autumn in Queensland but mostly during spring and summer in further south.
Australian smelt in ponds
This species because of its abundance in some parts of its range, is an important forage species for larger, predatory fishes; it was for this reason that it was introduced into Tasmania.
In ponds, they are excellent candidate especially because of their ‘frog friendly’ status this is because they are unable to eat the eggs from frogs, they serve an important addition especially small backyard pond where the owner doesn’t want to keep large fish but wants to control mosquito breeding.
In larger ponds, they are good addition to add to diversity. They can also be use as forage or feeder fish. Due to the fact that part of their life cycle does not require them spending anytime at sea, it is possible for them to breed right in ponds.