Changes in the freshwater environments of the Australian lungfish, in south-east Queensland
Kemp, A. (2020)
This paper assembles evidence collected over several decades to conclude that populations of the Australian lungfish in south-east Queensland are not reproducing sufficiently to guarantee survival of the species in the region. The environment of the Australian lungfish (Neoceratodus forsteri) has been altered over the past 50 years. Biodiversity of plants and animals has been lost. Water impoundments without effective fish transfer devices have been built over rivers. Submerged aquatic plants used by lungfish as spawning sites and refuges for the young have been significantly reduced in numbers, and food animals are absent or much less common. Lungfish used to spawn in a number of habitats in rivers and lakes in natural and translocated environments in south-east Queensland, in response to increasing photoperiod in spring. Oviposition events were cyclical, rising from low levels to a peak in successive years and then falling again. High levels of recruitment have, in the past, followed high levels of spawning activity, but recruitment depends on other factors as well. It should be noted that, while the sole trigger for spawning is photoperiod, many factors influence recruitment, such as food availability, refuges for young fish and the effects of predation, as well as the amount and type of food gathered by adult lungfish prior to the spawning season, and whether adults have been able to supply the eggs with appropriate nutrients. Spawning, and the survival of young, are now affected by environmental degradation, with extensive loss of biodiversity in freshwater environments where lungfish live. More to the point, recent attempts to use 14C dating to assess the age structure of lungfish populations are flawed and do not support claims that recruitment in lungfish habitats is continuing. Data on spawning included in this paper, and recent reports of recruitment success in several habitats, indicate that this is not the case.