In south-western Australia, the Canning, Southern and Wungong rivers provide vital freshwater habitats that support endemic aquatic biodiversity. However, these waterways are under increasing pressure from urbanisation, pollution, sedimentation, habitat degradation, invasive species and modified flow due to regulation and climate-induced rainfall reduction.
Targeted management action to safeguard waterway values, requires an understanding of minimum habitat criteria for healthy communities of endemic freshwater fauna. To address this need, we intensively surveyed the biodiversity of ten river pools for a period of one year, focusing on fish, crayfish, turtles, macroinvertebrates and the threatened Carter’s freshwater mussels (Westralunio carteri), together with water and sediment quality, river flow and in-stream habitat. Overall, we recorded >20,000 fish and crayfish comprising ten endemic and nine introduced species. We used visible implant elastomer (VIE) and passive integrated transponder (PIT) tags to understand residency and population sizes within pools, as well as connectivity between pools for native species. We found that populations of the iconic freshwater cobbler (Tandanus bostocki) and the oblong turtle (Chelodina oblonga) were more connected and in higher numbers than expected.
Through these extensive surveys, minimum habitat criteria for endemic freshwater fauna were identified. Following stakeholder consultation (including Whadjuk Noongar representatives, local government and landcare groups), these criteria are now being applied in a habitat enhancement trial in one of the pools. The trial will include the introduction of in-stream and riparian habitat to improve habitat health and complexity and facilitate river-bed scouring to create and maintain deep-water refuges. The baseline data presented here will be used to evaluate the success of the habitat enhancement trial in meeting ecological objectives.