Entrainment of fish through different types of irrigation infrastructure was investigated in the Fitzroy Basin, Queensland. The Fitzroy Basin contains a mix of tropical species typical of more northern catchments and species that occur in the Murray-Darling Basin and south-east coastal catchments. Types of infrastructure investigated included pumped and gravity fed diversions from Fairbairn Dam and riverine irrigation pumps on the Nogoa, Comet and Mackenzie Rivers. Riverine pump intakes included deep bankside intakes, shallow bankside intakes, deep mid-river channel intakes and intakes from the end of short, shallow channels excavated perpendicular to the river. Riverine pumping rates ranged from 14 ML/day to 164 ML/day.
The gravity fed diversion entrained more fish than the pumped diversion with mean values of 196.9 fish/ML and 9.1 fish/ML respectively. Riverine pumps had daily entrainment rates ranging from 0.6 fish to 137.2 fish /ML with a mean entrainment rate of 29 fish/ML. Bankside shallow intakes stood out as having much lower entrainment rates than the other riverine pump inlet types, such that a large (150 ML/day) bankside shallow intake was entraining fewer fish than smaller pumps on the other intake types. The most susceptible species to entrainment through the riverine pumps were olive perchlet and spangled perch. It is thought these species may have been actively swimming into pump intakes, looking for access to off-stream wetland habitats. Some entrained catches of these fish were biased towards larger adults compared to the riverine population. Data from this study can be used to help prioritise irrigation infrastructure for screening.