Climate neutral and biodiverse regional ecosystems

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Mapping fish migrations to revive our rivers

The value of water – for whom, where and when?

The Murray-Darling Basin is the drainage basin for six of Australia’s longest rivers, and covers most of New South Wales and Victoria, parts of both Queensland and South Australia and the Australian Capital Territory. Water drawn from the Basin supports more than 40 per cent of Australia’s agriculture production by value. From the time of European settlement, the Murray-Darling Basin has seen the construction of dams and weirs, with extensive regulation, diversion and extraction of water. Every drop of water going downstream now has a recognised owner and an allocated purpose, and there is only ever ‘surplus’ water during major flood events.

Despite water being the lifeblood of the region, flows have become incredibly disconnected among rivers due to dams and weirs. Many rivers have experienced decreased runoff, intermittent flows and more ‘ponded’ weir pools, making them increasingly disconnected from their tributaries and floodplains. Depending on the demand for water at particular places and times, river height may vary by up to 50 per cent of the channel depth over the course of a single day, and when there is no demand for irrigation water, flows are often turned off and entire channels can run dry.

The loss of dynamic and seasonal water flows, increase in no-flow periods and periodic disconnection of tributaries, streams, pools and lowland floodplains has had consequences for the natural environment, and the various habitats it affords the creatures living in it.

Particularly fish. Native fish populations in the Murray-Darling Basin have declined by over 90 per cent since European settlement.

The Murray-Darling Basin Authority has implemented the Basin Plan to manage water resources in the national interest, which includes improving ecological conditions and protecting habitats. The environment is represented by the Commonwealth Environmental Water Holder (CEWH) as the single largest ‘owner’ of water in the Basin, and it is responsible for providing ‘environmental flows’ to provide ecological benefits along the 2,000 km Murray River to the sea in South Australia. Even with environmental flows reinstated, many of our native fish populations are in a perilous state.

Water for fish – where and when?

The question then becomes “what environmental flows – when, where, how much and how often – do our fish actually need to thrive, and repopulate across the breadth of the Basin?”

It is a question that has intrigued Dr Ivor Stuart, Associate Professor of Fisheries at the Gulbali Institute, Charles Sturt University, for the last 30 years. “There are a lot of different interconnected issues caused largely by dams and weirs, but the biggest issue we’re tackling is restoring connected flow pathways for migratory fish,” he explains.

Migratory fish are most affected by changed water flow conditions in the Murray-Darling Basin, as they move between different habitats many times over the course of their lives, for spawning, feeding and growing. The indicator species Dr Stuart is focusing on is the golden perch, a medium-sized (3 kg), long-lived (more than 20 years), highly migratory fish that used to be prevalent across the Basin, but which is now contracted to fragmented populations in the more unregulated regions.

“In a sense, the golden perch are emblematic of all of the other native fish in the Basin,” explains Dr Stuart. “If we can get the conditions right for golden perch to survive, a highly mobile animal with a complex life history, it will also benefit the rest of the fish community with simpler life histories and more limited ranges.”

Seasonal water flow pulses, together with seasonal temperature changes, prompt golden perch to migrate and spawn every year. Their eggs passively drift with the water flow, eventually migrating their larvae into floodplain nursery habitats downstream that support juvenile growth. The survival of larvae and juveniles each year is closely linked to high flows or flood conditions, giving rise to age-related cohorts of fish associated with specific floodplain connection events. The riverine spawning habitats, long-distance drift and floodplain nursery habitats for juvenile fish, such as the Menindee Lakes, are now being recognised.

However, new technology developments and an environmental crisis have provided an opportunity for Dr Stuart to track the early life cycle of the golden perch.

After three years of drought and long periods of zero-flow conditions in the Barwon-Darling River, rainfall in the northern and eastern parts of the Basin brought drought-breaking flows in the catchment in 2020. The NSW Government protected these flows from water extraction to help the region’s highly stressed riverine ecosystems and fish populations recover. The conditions provided an opportunity for a collaborative research team from Charles Sturt University and NSW Department of Primary Industries and Regional Development to measure the timing and extent of spawning in response to the rare long-distance flow event.

“We had to resort to otolith chemistry and genetic techniques to identify and measure the age of individual larvae,” explains Dr Stuart. “Otoliths are bony structures found in the inner ear, and they accumulate layers of calcium carbonate as the larvae and fish grow. You can count the layers to measure the larvae’s age, similar to counting tree rings.”

Golden perch larvae were captured at sampling sites across more than 1,600 km of the Barwon-Darling River and three of its major tributaries, with their size and age distributions indicating spawning had occurred in both the mainstream river and the tributaries, with the flow then dispersing larvae hundreds of kilometres down into the Menindee Lakes.

“From this tracking work, and the fish surveys we undertake every year, we now know where the golden perch spawn, how they connect to the nurseries, and can see that strong year-cohorts of young fish are associated with floods,” says Dr Stuart. We need significant flow events, and connected river systems spanning 500–1,000 km to waterholes and floodplains to ensure widespread spawning, and juvenile survival.”

Dr Stuart and his team have subsequently tracked the dispersal of juvenile golden perch from the Menindee Lakes further downstream into the lower Darling-Baaka River and the connected Murray River system. “Some of these juvenile fish travel over a thousand kilometres,” he reflects. “Many of the adults spawn in the northern reaches of the Darling River towards Queensland. Eggs and larvae drift down through the Menindee Lakes, down through the lower Darling-Baaka River, growing larger, and then they disperse into the Murray River.”

Dr Stuart is now trying to identify the flow cues for dispersing juvenile fish into longer-term receiving tributary and mainstem Murray habitats that provide shelter and food. “We know that a year after the flood, these juveniles are on the move, but we previously never knew where these fish went, or why.”

By tagging and acoustically tracking these migrating fish, researchers from Charles Sturt University and NSW Department of Climate Change, Energy, the Environment and Water, with funding from CEWH, are slowly identifying how dispersing fish spread into the Murray River and tributaries like the Murrumbidgee and Edward-Wakool systems where fish might stay a year or two and mature, alongside adult fish making return visits to these supportive habitats. “We’re starting to work out which locations the fish are targeting in response to environmental flows and connected habitats, what attracts juvenile fish back into the mid and upper reaches of the Murray system.”

Mapping the fish life cycle to the water cycle

It's all building a picture of how environmental water flows can best be managed to support both spawning migrations, and the dispersive migrations of young fish. “For example, if we have a flood event, where fish spawn and survive, we know where we need to support environmental water flows in specific tributaries a year later to enable these juvenile fish to get where they want to go and continue their life journey.”

It's a global-stage migration for these fish, as Dr Stuart points out: “We’re seeing 2,000–3,000 km journeys for some of these fish by the time they’re three years old. And although efforts to track movements of these fish began in the 1970s, we’re only now filling in the blanks on the crucial first year of their lives, and the river conditions and habitats they need to survive past that, so they can mature enough to head back upstream and spawn themselves.”

It's information that all feeds into environmental water planning for the Murray-Darling Basin to better coordinate multi-year water flows across catchments, communities and states to recover our native fish populations and revive our rivers.

Impact summary

  • Research areas: native fish population management, environmental recovery
  • Research problem: tracking golden perch movement across its early life cycle and its migratory response to environmental water flows
  • Collaborators/countries: NSW Department of Climate Change, Energy, the Environment and Water, Commonwealth Environmental Water Holder, NSW Department of Primary Industries and Regional Development
  • Outcomes: multi-year environmental water flow strategies to coordinate spawning, dispersal and recruitment of native fish populations across the Murray-Darling Basin
  • Impact: improved dispersal and resilience of native fish populations, improved health of riverine ecosystems in the Murray-Darling Basin
  • Beneficiaries: fish populations and the natural environment, while still enabling water access for other users across the Basin

Golden perch

Future-proofing the Aussie grains industry

The Cool Soil Initiative at Charles Sturt is a paddock-to-product partnership. It supports farmers in exploring their practices to improve the health of their soil, increase their yield, and reduce on-farm greenhouse gas emissions. The purpose of the Cool Soil Initiative is to enable a scientifically credible framework for the food industry to support farmers in making a healthier, sustainable future for our farming industry.

This initiative aims to help farmers improve soil health and deliver greater yield and profitability while also pursuing the reduction of on-farm GHG emissions.

The team works with farmers growing hard wheat, soft wheat and irrigated corn in NSW and Victoria, providing on-ground support to farmers, soil tests and GHG emission reports. Farmers are also supported in testing new practices to improve the resilience of their system, including improved soil health. The team are also adapting the Cool Farm Tool, an online GHG calculator suited for commodity supply chain reporting, to suit Australian conditions.

The critically endangered Stocky Galaxias breeding program

Researchers at the Gulbali Institute, led by Dr Amina Price, have successfully bred the critically endangered Stocky Galaxias in captivity for the second consecutive year. In 2023, the Institute marked a groundbreaking achievement with the world's first hatching of these delicate fish under controlled conditions. And now, the team's hard work has paid off again, with almost 500 babies happily swimming in our aquatic lab!

The fish are only known from one stream, located high in the Snowy Mountains (and only 22km long!). To replicate Alpine conditions, the team needed to build a unique laboratory. They also needed to replicate the year's sunrise/sunset and seasonal changes. It took several years of trial and error to find the right mix of conditions, and the 'bumper' breeding year represents a significant milestone for the long-term survival of this species.

See the full story on Charles Sturt News.

Dr Amina Price next to specimen plate containing fish eggs. Collage images of hatchlings and baby fish

Research futures

Crop protection, soil science and agronomy

Professor Leslie Weston discusses her ground-breaking work in crop protection, soil science, and the use of various technologies to solve complex agronomy problems.

Partnerships and measuring ecosystem biodiversity

Professor Alan Cooper discusses Charles Sturt’s unique partnerships and strengths in a regional context, and his big idea to develop verification systems for measuring ecosystem biodiversity using DNA technologies.

Climate neutral and biodiverse regional ecosystems

The second challenge is to nurture climate neutral, biosecure and diverse ecosystems – our research here aims to reduce carbon emissions through the use of new technologies that allow us to test and forecast the effectiveness of different methods for both affecting pollution control and living hot –
that is thriving and surviving on a warming planet.

Research that reduces carbon emissions through renewable energy production, the use of biomass and natural capital and nurtures the ecology of freshwater, terrestrial and marine ecosystems.

We support the United Nations Sustainable Development Goals

Charles Sturt University aligns our research, policies, procedures, and other work with the UN Sustainable Development Goals (SDGs). These are the most relevant SDGs for this initiative.

Goal 07 - Affordable and Clean EnergyGoal 13 - Climate ActionGoal 14 - Life below WaterGoal 15 - Life on LandGoal 17 - Partnerships for the Goals

Recent funding

  • $1,605,601

    Methane throughout the beef cattle production cycle in southern NSW

    2022-2025

    Dr Shawn Russell McGrath

  • $418,712

    Determining the effect of wheat morphological and anatomical traits on frost susceptibility of wheat

    2023- 2026

    Dr Felicity Anne Joyce Harris, Grains Research & Development Corp

  • $2,169,195

    Cool Soil Initiative - Fast-track on-farm impact from the CSI

    2023-2026

    Fiona McCredie, Director Cool Soils

    Learn more
  • $4,000,000

    Australian Hazelnut five-year program

    2023-2029

    Professor Geoffrey Michael Gurr, AgriFutures - Australian Hazelnut Five-Year Program of research

  • $491,548

    Impact of stubble height on cropping systems in the Western Region, 2023-2025, Dr John Christopher Broster

    2023-2025

    Dr John Christopher Broster

  • $3,077,181

    Meat & Livestock Australia Limited

    2024-2026

    Professor Jane Catherine Quinn

  • $750,000

    CRC for High Performance Soils

    2024-2027

    Associate Professor Richard Jegatheeswaran Culas

  • $519,631

    Fisheries Research and Development Corporation

    2023-2026

    Professor Marta Hernandez-Jover