Tech & Science Endangered Murray hardyhead fish found spawning in a secret lagoon still kept under wraps

21:30  08 november  2019
21:30  08 november  2019 Source:   abc.net.au

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a man standing next to a body of water: Wetlands officer Stephanie Robinson undertakes fish testing at an undisclosed location. (Supplied: Department for Environment and Water)© Provided by Australian Broadcasting Corporation Wetlands officer Stephanie Robinson undertakes fish testing at an undisclosed location. (Supplied: Department for Environment and Water)

Deep in a secret lagoon in South Australia's Riverland a nationally endangered freshwater fish has been brought back from the brink to become a spawning species.

The Murray hardyhead is a small, native fish that was once found right across the Lower Murray River and Lower Lakes, but today it only survives in a small number of locations.

It was originally detected in the secret spot in April, and just over half a year later researchers have discovered the species is breeding.

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Natural Resources SA Murray Darling Basin wetlands project officer Stephanie Robinson made the discovery when undertaking regular salinity testing of the site.

"I was incredibly excited. This honestly is one of the best parts of my job," she said.

"Out of the 84 [fish found] we saw pregnant females, spawning males, and were also fortunate enough to see a cluster of Murray hardyhead eggs."

Strength in numbers

Ms Robinson said it was vital to ensure the location of the fragile fish remained undisclosed to ensure its survival and growth in numbers.

"Because it is an endangered species, our main aim now is just to make sure that it is protected and we continuously monitor it and look after it," she said.

The wetlands officer explained it was working partnerships with other local Landcare and conservation groups that helped maintain salinity levels for Murray hardyheads.

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"They can tolerate salinity levels of 100,000 EC [electric conductivity], whereas their eggs can only tolerate 20,000 to 30,000 EC," Ms Robinson said.

"In comparison, the river sits at about 200 to 300 EC and the sea sits at about 50,000.

"That's why it's really important that during the spring time, environmental water gets pumped in here for freshening to give them the best possible chance of survival."

Environmental water making a difference

To keep the secret location healthy, water flows have been pumped in by the Commonwealth Environmental Water Holder.

The water holder's local engagement officer Michelle Campbell said this was the water given up by irrigators in 2012 in exchange for on-farm infrastructure project funding.

She said the amount of water being delivered to support the Murray hardyhead is different to other sites as it is about meeting the desired objective.

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"The great thing about these wetland sites is they don't need a lot of water," she said.

"On average it's around 20 gigalitres a year that's used across wetlands sites from the South Australian border down to the Coorong."

Ms Campbell said the Commonwealth Environmental Water Holder is always consulting with communities to determine what projects will receive flows.

"The science, over many years, has basically shown if you just add water to these flood plain habitats things get better," she said.

"But because there is so little water we have to be so careful with how we use it. We really have to target what we are using it for at these sites."

How did the fish get there?

The Murray hardyhead are thought to have populated the body of water during a high water event several years ago because it is not connected to the main river.

Nature Foundation SA Water for Nature program manager Natalie Stalenberg said the salinity of the lagoon does the fish a favour.

"The Murray hardyhead can tolerate that high level of salinity whereas their predator species can't. So they are at an advantage there," she said.

"It's a careful balance of managing those salinity levels.

"[It's about keeping enough fresh water] for the breeding, but not enough for other species."

South Australia's Riverland is not the only place that the Murray hardyhead will live and continue to breed.

The Federal Government has relocated some of the fish to a wetland in far western New South Wales after several years of work was undertaken to identify a suitable habitat.

It is the first time in more than a decade that the Murray hardyhead has been in New South Wales' waters.

Back at the secret lagoon, Ms Robinson hopes to help the threatened fish and other species thrive into the future.

"The most important things are to understand the ecology of your species, work together to maintain that environment for them, and overall protect them," she said.

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