Georges River Fish Habitat Restoration Project

OzFish Hawkesbury-Nepean Chapter with Campbelltown Council have been undertaking Environmental DNA (eDNA) sampling in south-west Sydney on the Georges River to determine the presence of endangered species in the waterway.  Local volunteers assist researchers and staff from council by collecting water samples in a coordinated approach at various locations along the river to determine whether platypus and the elusive Macquarie Perch (Macquaria australasica) are still present in the system.

The results are promising…

Traces of Macquarie perch (Macquaria australasica or Maccas) DNA have been found in the Georges River for the first time in 30 years. The Georges River, located in New South Wales, runs from the Dharawal National Park to Botany Bay in south-western Sydney. The river is home to diverse native flora and fauna but many of the species are often difficult to locate using traditional survey methods. The Platypus Pals Project endeavours to track platypus and other hidden species that are difficult to locate, using eDNA (environmental DNA) testing of water samples in the Upper Georges River. 

The Macquarie Perch, also known as the ‘Macca’, has become an endangered fish in the Murray-Darling Basin and south-eastern New South Wales, with only a few small, vulnerable and isolated populations left in the wild. The Macca requires a very specific habitat; ideally fast-flowing, rocky water with shady trees and bushes along the banks, which can be found in the Georges.

The Upper Georges River. Photo credit: Georges Riverkeeper.

These habitats have been reduced through agricultural and urban development, drought and bushfires in many regions, including the Georges River. These impacts are also compounded by a number of introduced species which predate on the Maccca, such as the Redfin perch and Carp. In addition the Redfin perch carry a lethal virus, the Epizootic Haematopoietic Necrosis virus (EHN), which the Maccas are highly susceptible to catching. We now know that where there are Redfin perch, there is unlikely to be Maccas – this is another reason why the Georges River is such an important reach as there are currently no known Redfin perch in the river.

What is eDNA?

EDNA (or environmental DNA) is a non-invasive way of monitoring species and is especially useful for waterways that are difficult to access or where traditional surveying methods could cause harm to the ecosystem or species. 

Collecting a water sample for eDNA testing. Photo credit: M. Schwartz, USDA.

Water samples of around 200-400ml are collected from the waterway by community members or scientists and then passed through a DNA retention filter. DNA is then extracted from the filtered water and the DNA is amplified (replicated multiple times). The mitochondrial DNA from each sample is then compared to the DNA sequences of each available species’ sequence to assess its presence.

Diagram of the eDNA process. Source: Liam Whitmore, University of Limerick and The Conversation.

Macquarie perch DNA was promisingly found in six of the 19 sites that were tested in the sampling undertaken in September 2020.

So, what’s so special about Maccas in the Georges?

The Macquarie perch is an endangered species that has seen a population decline from human-induced changes to its environment. Notably, overfishing, habitat degradation, overregulation of water flows and thermal water pollution by dams have caused significant challenges to the species’ survival. Even more recently, fires and floods in the area have significantly impacted on the Maccas habitat, worrying some fish scientists that the species had become extinct in the area. 

Maccas haven’t been found in the Georges River since the 1990s, so this evidence of their e-DNA presence is exciting for fish conservationists. As explained by Campbelltown Mayor George Brticevic, “these results will help to inform future community-focused programs and education that will help to conserve these important and unique native animals”. The confirmation of their presence helps target habitat rehabilitation work and control of threatening processes in the Georges River. 

Joshua Oates, Campbelltown mayor George Brticevic and Campbelltown MP Dr Mike Freelander collecting eDNA water samples for the Platypus Pals project. Source: Chris Lane.

With thanks to the great team at OzFish.
The original story for this terrific project can be found here…

The project was made possible with support from Campbelltown Council; Macarthur Federal MP Dr Mike Freelander through the Federal Government’s Communities Environment Program, the OzFish Landcare NSW partnership and funding support from the NSW Recreational Fishing Trusts, BCF – Boating, Camping, Fishing and Tate Endowment Fund. 

Featured image: The endangered Macquarie perch (Macquaria australasica).
Source: E. Beaton, ACT Government.

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