ABSTRACT
Th e Australian lungfi sh Neoceratodus forsteri is the only extant member of a rich lungfi sh fauna known primarily from Mesozoic and Cenozoic deposits in Australia. Present day lungfi sh populations are confi ned to a series of coastal river systems within the south-east corner of Queensland. However, fossil evidence confi rms that N. forsteri previously occupied a more extensive distribution. Th roughout their distribution, Australian lungfi sh inhabit river channels and tributary streams upstream of the tidal interface. Th e life-cycle is completed entirely within freshwater reaches with an annual spring/summer breeding season. Spawning activity is concentrated along shallow river margins, with eggs deposited in dense beds of aquatic plants or amongst the submerged rootlets of riparian vegetation. Developing embryos are subject to a range of threats including predation, fungal and bacterial infections, fl uctuating water levels and physical damage. Th e incubation period varies according to temperature but generally extends for 23-30 days. Th e diet of N. forsteri changes over time refl ecting a progression from larval to adult dentition. Recently hatched and juvenile lungfi sh feed largely on small invertebrates, while adults ingest large amounts of plant material as well as a range of invertebrates, small fi sh and tadpoles. Australian lungfi sh are predominantly nocturnal and occupy restricted home ranges around 1-1.5 km in length. Movements outside the home range are most commonly observed when individuals seek out suitable spawning habitat prior to the annual breeding season. However, longer movements can occur at any time and are frequently associated with instream fl ow events. At rest in well-
aerated water N. forsteri rarely breathes air, respiration being supported almost entirely by the gills. Air breathing is used primarily to supplement short-term oxygen demand during periods of increased activity and is most commonly observed during courtship behavior and during fl ow events. Th e Australian lungfi sh is a slow-growing and longlived species that reaches a maximum total length of approximately 1500 mm. However, the dominant size class in most surveys is 900-1000 mm. Sex ratio has been reported as approximately even, with largest size classes (>1200 mm) dominated by females. Males mature at a smaller size than females. Th e species exhibits low allelic diversity at allozyme and mitochondrial loci with little evidence of genetic diff erentiation between catchments within the distribution. Debate over the conservation status of Australian lungfi sh has continued for over a century, primarily because juvenile lungfi sh are diffi cult to collect from the wild. Th is issue, coupled with the lack of a reliable method for ageing lungfi sh has hampered eff orts to understand the population dynamics and true status of the species. Following European settlement, all the major rivers inhabited by N. forsteri have become progressively more regulated and degraded. Recent evidence indicates that successful spawning and recruitment rarely occurs in the still waters upstream of the numerous weirs and dams in south-east Queensland. Th ese barriers are also restricting lungfi sh movements, raising concerns over the genetic structure of remaining populations. Th e species also faces other threats including introduced species, habitat alteration, stranding events and reduced water quality. Current management strategies are focussed on reducing adult mortality, improving connectivity between remaining populations and providing suitable habitat for successful spawning and recruitment. Keywords: Australian lungfi sh (Neoceratodus forsteri), Queensland, Ceratodus
“It will take considerable time before the Ceratodus is thoroughly understood; but it will come” (Welsby 1905). Th e Australian lungfi sh drift ed quietly into the scientifi c spotlight on the morning of January 18th, 1870. In a letter to the Editor of the Sydney Morning Herald, Head Curator and Secretary of the Australian Museum, Gerard Krefft , described two unusual specimens, which he had received from the Wide Bay/Burnett District of south-east Queensland. Th e specimens had been procured by Krefft ’s long time friend and prominent politician William Forster, a former Queensland resident who had acquired large tracts of land in the Burnett Catchment. During their long friendship Forster had tantalised Krefft with tales of fi sh eaten by squatters along the Burnett and known locally as ‘fresh water salmon’ (Whitley 1929). Th e specimens presented to Krefft were collected by Forster’s cousin W.F. M’Cord of Coonambula, near Mundubbera. Krefft ’s initial examination was hampered by a lack of internal organs, which had been removed for transport to Sydney. Despite this obstacle he recognised the signifi cance of the specimens and described them as amphibians allied to fi sh from
the genus Lepidosiren. More remarkably, he also recognised that tooth plates from the specimens bore similarities to fossil material from an extinct genus of fi shes known as Ceratodus and previously described by Agassiz (1844) as selachians (sharks). Fulfi lling a promise to William Forster, Krefft named the new species Ceratodus forsteri in his letter and thus provided the fi rst scientifi c record of the Australian lungfi sh (Krefft 1870a). Th e letter was followed by a formal description including illustrations (Fig. 1), which was presented to members of the Zoological Society of London (Krefft 1870b), in which Krefft noted that: “It is strange that a curious creature like this, which was well known to the early settlers of the Wide Bay and other Queensland districts, should so long have escaped the eyes of those interested in natural history”.
