Among Australian fishes, the Australian Lungfish is generally regarded as the most unique and interesting, due to its strange features, restricted distribution and evolutionary lineage. It was first described in 1870, creating frenzied interest among the scientific community. Along with several African and South American lungfishes and the Coelacanth – another lobe-finned fish later discovered in the Indian Ocean – they are often purported to be surviving links in the evolutionary chain between fishes and amphibians. Similar species were once widespread, but are now only known from fossil deposits.
The Australian lungfish has a fully functioning lung as well as gills, although the lung is mostly used only when the fish is very active, or when the water becomes muddy or low in oxygen. It can survive out of water in drying river beds, billabongs or gullies for extended periods, as long as it is kept moist in the bottom mud or aquatic weeds.
Early scientists from Britain and Europe came to Australia to research and discover more about the new and fascinating lungfish. Adults were readily caught, however juveniles were notoriously difficult to find, even in the late 1800’s, and zoologists became seriously concerned about long term survival of the fish.
The original distribution of the Australian lungfish was restricted to the Mary and Burnett River systems. Due to the perceived threats, specimens were translocated to the Enoggera Reservoir and North Pine, Brisbane, Albert, Coomera and Condamine Rivers in 1895-6, with the intention of broadening their distribution and thereby improving the viability of the species. Those transferred to the North Pine, Enoggera Reservoir and Brisbane River have resulted in self-sustaining populations. Small numbers may persist in the Albert and Coomera Rivers, but those in the Condamine did not establish.
It is estimated that Australian lungfish mature at between 10 and 20 years, and can reach at least 60 and possibly up to 100 years of age. A long-lived species with a low adult mortality rate does not need to successfully spawn annually, or in large numbers, to sustain itself. Spawnings of lungfish generally produce surviving juveniles only when conditions for both egg-laying and the growth of eggs and young are ideal, perhaps on average every 5 or so years. This explains why juveniles have always been difficult to find and why adults are much more commonly seen.
Australian Lungfish, Neoceratodus forsteri
Neoceratodus forsteri (Krefft, 1870)
Total length is up to 150 cm, but most commonly found at about 90 cm. Adults have greenish-brown back and sides and yellowish to salmon-pink belly, often with a few small, scattered, irregular black blotches. The scales are very large and overlapping. The pectoral and pelvic fins are paddle-shaped. The eel-like tail combines the dorsal, caudal and anal fins. Juveniles are mottled, with less colour contrast between upper sides and belly.
Prefers deep, slow-flowing waterholes in freshwater streams with dense banks of aquatic plants. Native to Mary and Burnett Rivers, but translocated to other rivers and lakes of southern Queensland, between the Coomera and North Pine Rivers.
Spawns in spring and early summer among aquatic plants and fine mats of tree roots along the river banks. Juveniles are uncommon and seldom seen. The lungfish is a protected species and a special permit is required to take or keep lungfish in an aquarium.