PHCC has recently teamed up with scientists from Murdoch University to conduct river health assessments across sections of the Murray River. These assessments will provide a snapshot of the current ecological condition of the river against which we can measure the success of future restoration activities in increasing the health and biodiversity of the river and its surrounds.
PHCC’s Healthy Waterways Team has linked up with researchers Dr David Morgan and Dr Stephen Beatty of Murdoch University’s Centre for Sustainable Aquatic Ecosystems to undertake assessments of the health of the middle and upper reaches of the Murray River, upstream of the Pinjarra weir to the foot of the Darling Scarp.
We assesses in-stream condition through trapping and measuring the abundance, species diversity and condition of native fish such as western minnows, pygmy perch, nightfish and black bream; native freshwater crayfish (glass schrimp, gilgies and marron) versus exotic species such as redfin perch yabbies and gambusia to score the “nativeness” of the river. The team also sweeps the in-stream vegetation with a net to collect macroinvertebrates (e.g. dragonfly and damselfly nymphs, beetles) which are identified under a microscopy in the laboratory to determine the species richness and abundance. The complexity of differing vegetation communities that inhabit the edges of the river are also assessed.
Each of these assessments and measurements are performed according to standardised protocols and are used to calculate the South West Index of River Condition (SWIRC), developed by the Western Australian Government Department of Water and Environmental Regulation. When repeated with consistency, these assessments will measure changes in the condition of the river over time and help us evaluate the effectiveness of rehabilitation and management actions in and around the Murray River.
The team preformed assessments at three sites in the middle to upper reaches of the Murray River in autumn 2021, at a time of year when freshwater in-flows to the river are usually low. The results revealed that even the most upstream sites towards the Darling Scarp were in fact saline but well oxygenated, providing relatively good water quality to support abundances of native fish including freshwater cobbler, western minnow, western pygmy perch, nightfish, western hardyhead, bluespot goby and the southwest goby. Glass shrimp displayed signs of a healthy population and smooth marron and gilgie were also present but in low abundances. The exotic species of eastern gambusia was also identified across the three sites, in encouragingly low numbers.
The sites will be sampled again this spring when in-flows are usually at their highest to allow an assessment of seasonal changes in aquatic communities. These River Health Assessments will complement the River Action Plans for both the Lower (below the Pinjarra weir) and Middle sections of the Murray River which indicate areas that are in need of restoring and guide restoration works for years to come.
If you would like to find out more about these assessments, how they operate and the number of sites across W.A, please head to the Department of Water and Environmental Regulation’s Healthy Rivers website.
The project is supported by the Peel-Harvey Catchment Council through funding from the State Governments Royalties for Regions and the Alcoa Foundation’s Three Rivers One Estuary Initiative.