A group of scientists and traditional owners is carrying out a complete audit of one of Australia's most intriguing and vulnerable rivers.
Queensland's Mary River is home to a treasure trove of rare and endangered species.
The most famous is the prehistoric Australian Lungfish, or what traditional owners call Dala.
There's also two species of freshwater turtles that have the bizarre trait of breathing out of their bottoms.
But these species face ongoing threats.
Two hundred years of farming along the banks of the Mary has removed much of the tree cover, and the river is becoming increasingly vulnerable to the damaging effects of floods.
Scientists, community groups and traditional owners have joined forces to carry out the most comprehensive survey ever of the Mary River.
And they've done this the old-fashioned way, paddling 200 kilometres along the waterway by canoe.
Expedition organiser, ecologist and director of research with the Burnett Mary River Group, Tom Espinoza, says it's the best way to find out what's really going on.
"Until you canoe and paddle it and set some nets like we've been doing, that's when you start to understand what a river is and what the river needs," he says.
"That's when you start to understand what a river is."
The idea is to put a true value on the river in the hope of attracting investment to better protect it.
CEO of the Burnett Mary River Group, Sheila Charlesworth, said the survey will feed into a bigger project called Accounting for Nature.
"We measure all structural assets, buildings and mines ... yet we have this wonderful, beautiful country that we're not measuring, our natural assets – so it's crucial that we actually start to do this," she says.
The involvement of traditional owners is an essential part of the expedition.
The Mary River begins in Jinibara Country in the hinterland of the Sunshine Coast.
It makes its way through Kabi Kabi country before finally flowing through Butchulla land to the Great Sandy Strait.
Kabi Kabi traditional owner Norman Bond says the river is filled with significant sites and material.
"It may have been over 100 years since our people traversed down the river knowing that it's freehold now," he says.
"What we're doing here is very special," says Butchulla traditional owner Conway Burns.
"We've seen some sites where it has really opened our eyes ... we've walked in our old people's footsteps, so to speak."
Treasures almost lost
Many of these cultural and environmental treasures would have been lost if a plan to dam the river around the Traveston Crossing went ahead.
In 2009, the then federal environment minister Peter Garrett effectively blocked the dam on the grounds that it posed an unacceptable risk to threatened species such as the Australian Lungfish, the Mary River Turtle and the Mary River Cod.
"It's quite unique in this part of Australia, this central eastern part of Australia, not to have a big dam," says Professor Mark Kennard, from Griffith University's Australian Rivers Institute.
But today the river still needs help.
And documenting the current state of the Mary is an essential first step in putting together a comprehensive protection and rehabilitation plan.
"I'm surprised at how good some parts of the habitat is, and how bad some of the habitat is," says Tom Espinoza.
"It's from waterhole to waterhole that you see that contrast."
Scars on the river banks
The scars from last year's record-breaking flood are clear to see, with widespread scouring and loss of topsoil.
The sediment from erosion along the banks of the Mary River ends up in the catchment of the Great Barrier Reef.
"The biggest threat has already happened," says Jason Murphy, a Jinibara traditional owner.
"There's been a lot of clearing – clearing right up to the banks."
Community groups such as The Mary River Catchment Coordination Committee say it's essential to document which rehabilitation programs are working best.
"Over the past 20 years many landholders have been rehabilitating their riverbanks, with tree-planting and weed control, which were clearly evident during the canoe-based assessment," a committee report says.
Endangered species thriving
It's also important to document the growing number of feral species in the river.
"We're seeing more and more invasive fish species," says Professor Kennard, whose research is supported by the National Environmental Science Program, Resilient landscapes Hub.
Of particular concern is the growing number of Tilapia – a fish native to southern Africa that was introduced into North Queensland about 20 years ago, and the Barred Grunter.
"There's also a lot of weeds along the river, the riparian zone," Professor Kennard says.
Spirits are lifted when the expedition discovers good habitat for the endangered Mary River Cod, and a landholder shows us a baby Mary River Turtle – one of the 400 hatchlings he introduced into the river a few weeks earlier.
Only a few are expected to survive, and their survival technique is the sheer weight of numbers.
"Anything in the river will eat them," says Tom Espinoza.
"Wait until you get big enough not to get eaten is the trick, I think."
These small turtles are a particular favourite of the native catfish.
But every morning the river nets reveal there is still evidence these rare and endangered species are thriving.
Over two days, 7.30 saw three Australian Lungfish in the nets in the Mary's lower catchment. There were two adults that could be anywhere between 40 and 100 years old, and one juvenile.
"These younger ones are very unique and rare – they're very important, showing that the system is still producing recruits and producing conditions that enable spawning," Mr Espinoza says.
Australian Lungfish have a single lung and they breathe both in and out of water.
"That's probably helped them in times of drought," Mr Espinoza says.
7.30 is shown a scale from a lungfish – it has a leathery feel, more like a piece of armour than a fish scale.
Professor Kennard explains how the scales can help reconstruct the lungfish's history.
"We get isotopes of nitrogen and carbon, and for each part of the scale we have an age on it and what they were eating."
"They're a very unique species, very scientifically important," says Tom Espinoza.
"Some of the structures in their limbs are believed to be some of the first that crossed from life aquatic to terrestrials."
And there was much excitement at the sight of a large Mary River Turtle in the nets.
Tom Espinoza says he's seen a "good number" of these endangered turtles over the years.
"Particularly in the upper catchment, but they are down here as well."
The turtle is measured and then returned to the river.
The Mary River Turtle can extract oxygen from the water through a gill-like structure in its cloaca, and is often referred to as a "bum-breather".
Another rare species – the white-throated snapping turtle – also has this bizarre ability, and it was spotted near one of the expedition's camp sites.
These observations are all part of the first, but hopefully not the last, comprehensive assessment of one of Australia's most intriguing rivers.
And after 10 days on the river, the scientists and traditional owners say they've learnt from each other.
Jinibara traditional owner Jason Murphy said it was "cool" working with scientists. "You also find the systems they use so they can share information with other people," he said.
"They were always connected in the past," says Tom Espinoza. "And what we're trying to do now is not only to reconnect them, but also to reconnect us."
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Credits
- Reporter: Peter McCutcheon
- Photography and Videography: Chris Gillette, Curtis Rodda. White-throated snapping turtle video supplied by Caitlin Mill, Mary River Catchment Coordinating Committee.
- Graphic Design: Eric Hao Zheng
- Digital Production: Jenny Ky and Myles Wearring
