Impacts of river regulation and fragmentation on platypuses in the northern Murray–Darling Basin

Context

River regulation affect freshwater species by disrupting the natural flow regime and connectivity.

Aims

Investigate the impact of river regulation on platypus populations on four regulated rivers within the northern Murray–Darling Basin.

Methods

Assessment of hydrology, live trapping downstream of large dams, multi-species environmental DNA surveys in upstream and downstream sections.

Key results

There were significant changes in flow seasonality and cold-water pollution as a result of river regulation. Upstream sections experienced prolonged periods of ceased flow, most recently during an extreme drought between 2017 and 2020. eDNA surveys detected platypuses downstream of all dams but failed to find evidence of them upstream in two rivers, indicating possible local extinctions. Capture of four platypuses in the Severn River and four, in very poor condition, in the Peel River, and none in the Gwydir River or Pike Creek–Dumaresq River. Significant differences in macroinvertebrate communities, implying possible impacts on platypus diet.

Conclusions

River regulation and habitat fragmentation affect platypus populations, namely disappearance from upstream sections, low downstream capture rates and the poor body condition.

Implications

Urgent need for catchment-scale river management strategies that preserve ecological functions and connectivity and improve resilience to protect and sustain platypus populations, indicating directions for future research and conservation efforts.