3 – Fish distribution, status and threats 39 ambigua) from the Murray–Darling Basin were also introduced across a wide area. The negative effects on local populations of yellowbelly (potentially a separate species) were never considered, and the fate of these stocked fish remains unknown (including potentially breeding with local yellowbelly). In the 1990s, the large red claw crayfish (Cherax quadricarinatus) was also deliberately released, with considerable investment of resources. Red claw are native to north-eastern Australia but not the Lake Eyre Basin. They quickly established in the Cooper Creek, Diamantina and Georgina River catchments. It is assumed that individuals escaped from aquaculture populations and walked into the rivers. Dramatically, red claw exclude and out- compete the locally occurring blue claw yabbies (Cherax destructor) (Kerezsy 2010 B. Cockayne and D. Akers, personal communication). Most recently, the large bottom-dwelling gudgeon, sleepy cod (Oxyeleotris lineolate Fig. 3.5) – also from rivers in Australia’s north-east – has become established in the Cooper Creek catchment. The source population of sleepy cod in the Cooper Creek catchment is likely to be specimens that escaped from dams close to Longreach during flooding. The species was first caught in 2008, near Stonehenge on the Thomson River (Kerezsy et al. 2014), and is becoming increasingly common during recent fish surveys in the Cooper Creek catchment (B. Cockayne, D. Sternberg personal communications). The concern is that this large (up to 450 mm) and carnivorous species may also have a negative effect on the local food webs within Cooper Creek, particularly as waterholes dry during summer. Conclusion – now and the future Our current knowledge of fish communities throughout the Queensland Lake Eyre Basin indicates that native fish populations are in good condition, especially compared to other inland systems regulated by dams and extractions (e.g. the rivers of the Murray–Darling Basin). In stark contrast, the endangered spring communities, particularly those in the easternmost Barcaldine group, are still threatened by alien species (primarily gambusia but Fig. 3.5. Sleepy cod, naturally occurring in Australia’s tropical rivers, is a predator and was first detected in the Thomson River in 2008. The species is now well established throughout the Cooper Creek catchment (photo, A. Emmott).