SoE 2011 provided information on the pressure of invasive species, including cane toads (Rhinella marina, formerly Bufo marinus), common carp (Cyprinus carpio), eastern gambusia (Gambusia holbrooki), goldfish (Carassius auratus) and various Weeds of National Significance. Other invasive species exerting pressure on inland waters include pigs and buffalo, redfin perch (Perca fluviatilis), various tilapia species, oriental weatherloach (Misgurnus anguillicaudatus) and redclaw crayfish (Cherax quadricarinatus).
Cane toads have now spread into the Kimberley and upper reaches of the Fitzroy River in Western Australia (Pusey & Kath 2014), and inland western Queensland, with estimates of expansion of around 10–50 kilometres per year. Expansion in the cane toad range has been found to reflect a shift in the species’ realised niche (i.e. a shift aided by the presence of novel biotic and abiotic conditions in the invaded range), as opposed to the evolutionary shifts in range-limiting traits that affect the range of any species (Tingley et al. 2014).
The challenge of managing feral freshwater fish, and understanding their extent and impact has spawned a national online information resource, called Feral Fish Scan. Feral Fish Scan is taking a crowdsourcing approach to provide a community resource for mapping feral fish, which, over time, will provide further support for management. A heat map of carp extent in Australia shows areas similar to those reported in 2011. Increases have occurred in western South Australia, and central and southern Victoria (Figure WAT8). Detailed local monitoring may provide more accurate assessment of the presence and extent of feral species; for example, the Lake Eyre State of the Basin Committee found no carp in a survey of an area that may have formerly contained carp. There is also some evidence that carp numbers have increased since the 2010–11 flooding of the Murray River (Koehn et al. 2016).