Groundwater contribution to baseflow maintains habitat connectivity forTandanus bostocki(Teleostei: Plotosidae) in a south‐western Australian river

Beatty SJ, Morgan DL, McAleer FJ, Ramsay AR. Groundwater contribution to baseflow maintains habitat connectivity forTandanus bostocki(Teleostei: Plotosidae) in a south‐western Australian river. Ecology of Freshwater Fish 2010: 19: 595–608. © 2010 John Wiley & Sons A/S Abstract – A global biodiversity hotspot, south‐western Australia is characterised by a highly endemic freshwater fish fauna that is severely impacted by habitat alterations. As is the case with many rivers in this region, the Blackwood River is secondarily salinised as a consequence of agricultural practices and this has caused population depletions of halo‐intolerant fishes. This study is the first to examine the role that groundwater intrusion has in maintaining habitat connectivity for an obligate freshwater fish in a secondarily salinised river. We determined the significance of nonsaline groundwater intrusion in maintaining habitat and migratory routes of the freshwater cobbler,Tandanus bostockiduring prolonged annual dry periods; characteristic of Mediterranean climatic zones.Tandanus bostockiundertook large, yet spatially and temporally variable, localised movements through riffles. During baseflow, the period of major groundwater influence, movements were significantly associated with discharge. Analysis of gonadal development suggested that such movements were not strictly related to reproduction and were probably for foraging purposes. The study reveals groundwater is crucial in maintaining migratory routes through riffles and suggestsT. bostockimay be reliably used as an indicator of aquatic habitat connectivity in light of groundwater extractions and also continued rainfall reductions in this region due to climate change.