Connecting fish, flows and habitats on lowland river floodplains

Connectivity between river and floodplain habitats is important to many lowland river fishes enabling them to complete their life cycle, maximise growth potential and minimise early life-history mortality. There is increasing recognition of this need and in regulated systems, increasing sophistication of management processes and infrastructure around environmental water allocations to facilitate this connectivity.\nProviding connecting flows with limited water resources often means prioritising watering one area over another; so comparative evaluation of fish movement, growth and productivity can be important to demonstrate success.\nIn the Great Darling Anabranch, we used directional-netting, measures of whole stream productivity and fish otolith growth and body condition analysis to investigate benefits of connecting flows in 500km of restored ephemeral river channel alongside the same factors in an alternative flow-path, the Darling River.\nThe Hattah Lakes, a complex of regulated, lowland-river floodplain lakes can be filled using large, purpose built environmental pumps; transferring water and fish recruits from the Murray River to productive floodplain habitats. We investigated the lateral movement of resident fish during filling and draw-down of the lakes, using acoustic tags in a native fish species, Golden perch (Macquaria ambigua) and an invasive fish, Carp (Cyprinus carpio). We generated regular movement-trajectories for tagged fish using interpolation, then tested observations against null models to evaluate individual and group movements against a one-dimensional behavioural hypothesis; “do fish move towards or away from the river in response to draw-down or filling?”\nResults are assisting natural resource managers develop designs for environmental watering hydrographs for connecting flows in large anabranch channels and floodplain lakes.