Alleviating the loss: A conical fish screen installation reduces native fish entrainment at a gravity-fed water diversion

Each year, millions of fish are extracted from Australian waterways by the pumping and diversion of water into irrigation systems. Fish protection screens can help reduce these losses but are largely untested in Australian rivers. In this study, a large, gravity-fed irrigation offtake on Gunbower Creek, Victoria, Australia, was investigated for fish and debris entrainment. Experiments were performed under screened and unscreened conditions across various river flows. Mark–release–recapture experiments were undertaken with fingerlings of two recreationally significant fish species, Murray cod (Maccullochella peelii) and golden perch (Macquaria ambigua), together with wild fish community assessments, to determine how effective the screen was at reducing fish entrainment into the irrigation channel. The mean percentage of recaptured fingerlings was significantly lower when the irrigation channel offtake was screened compared with unscreened. Entrainment of released fish into the irrigation channel was reduced by >98%. Similarly, wild fish entrainment was significantly lower when the irrigation channel was screened. When screened, fewer wild species dominated the sampled fish community, and entrained fish were generally <40 mm in length. Debris loads decreased significantly in the irrigation channel owing to the screen, indicating the economic benefits of fish screens. Implementing screens could aid in native fish conservation efforts in riverine environments.