CSIRO PUBLISHING www.publish.csiro.au/journals/mfr Marine and Freshwater Research, 2006, 57, 619–633 Fish assemblages of an Australian dryland river: abundance, assemblage structure and recruitment patterns in the Warrego River, Murray–Darling Basin Stephen R. BalcombeA,E, Angela H. ArthingtonA, Neal D. FosterB, Martin C. ThomsC, Glenn G. WilsonD and Stuart E. BunnA ACooperative Research Centre For Freshwater Ecology, Centre for Riverine Landscapes, Griffith University, Nathan, Qld 4111, Australia. BNew South Wales Department of Natural Resources, PO Box 550, Tamworth, NSW 2340, Australia. CUniversity of Canberra, ACT 2016, Australia. DMurray–Darling Freshwater Research Centre, Goondiwindi, Qld 4390, Australia. ECorresponding author. Email:
[email protected] Abstract. Fish in dryland rivers must cope with extreme variability in hydrology, temperature and other environ- mental factors that ultimately have a major influence on their patterns of distribution and abundance at the landscape scale. Given that fish persist in these systems under conditions of high environmental variability, dryland rivers represent ideal systems to investigate the processes contributing to and sustaining fish biodiversity and recruitment in variable environments. Hence, spatial and temporal variation in fish assemblage structure was examined in 15 waterholes of the Warrego River between October 2001 and May 2003. Fish assemblages in isolated waterholes were differentiated at the end of the dry 2001 winter but were relatively similar following high summer flows in January 2002 as a consequence of high hydrological connectivity among waterholes. Small, shallow waterholes supported more species and higher abundances than large-deep waterholes. Large, deep waterholes provided impor- tant refuge for large-bodied fish species such as adult yellowbelly, Macquaria ambigua, and the eel-tailed catfish, Tandanus tandanus.