The effect of water quality, macroinvertebrate assemblages and habitat suitability on the distribution of Platypuses : a pilot study in Cattai Catchment, North West Sydney

![CDATA[The platypus (Ornithorhynchus anatinus) continues to persist in urban waterways with high pollutant concentrations, altered flow regimes, channel morphology, and degraded stream substrate and riparian zones. The purpose of this study was to determine whether water quality, specific habitat features, and macroinvertebrate assemblage influences the distribution of platypus as inferred by eDNA detection in a selection of 13 sites within the Cattai catchment, in North West Sydney. Sampling took place on two separate occasions: June 2020 and December 2020. Platypus eDNA was detected in 9 of the 18 sites and 5 of the 9 waterways surveyed. Platypus activity was strongly associated with the quality of their stream habitat (riparian vegetation, absence of sand and silt accumulation, and streams lacking dense growth of macrophytes). Platypus also appeared to avoid streams with ‘higher salinity', and lower dissolved oxygen. The effective conservation of this iconic species in peri-urban and urbanised catchments such as that of Sydney requires ongoing monitoring of population status and health, and prevention of further habitat damage by informed local population management strategies. This study indicates that the loss of riparian vegetation, an increase in aquatic weeds and increased sedimentation are important factors in developing local stream management improvements to sustain the population of platypus in the Sydney basin.]]