2023 – Managing Native Fish Populations During Reservoir Dewatering

C.D. Harvy, J.P. Newman, L. Thwaites, R.I. Daly, E von Wielligh

This paper presents a fish management framework for use during reservoir dewatering, which is often required for critical infrastructure upgrades. The framework considers the structure of the fish population, the value of relocating this population, and the effectiveness of relocation methods to minimise environmental impact. In addition, the framework considers the risk of fish kill events during dewatering, using ecosystem monitoring and modelling techniques. This paper demonstrates the value of the framework by presenting a use case to Warren Reservoir, which involved developing an ecosystem model, with oxygen availability used as an indicator of fish health, the application of live monitoring strategies and power hauling as a fish removal technique. Through the use of the framework, SA Water ensured that native fish were minimally impacted, and invasive fish species were removed during the dewater. Given recent experiences of fish kills in major Australian water bodies, this framework provides a way forward in managing fish health when dam upgrades disrupt their habitat.

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