Inside an aquarium on Queensland’s Sunshine Coast is a tank of tiny freshwater fish – each less than three centimetres long – that holds special significance for conservation in Australia.
This population of endangered red-finned blue-eye represents a new recovery initiative that may help to ensure the long-term survival of the species.
They’re the first stage of a captive-breeding program Bush Heritage is pioneering in partnership with Sea Life Mooloolaba (also known as Underwater World).
While other blue-eye species are found in coastal draining rivers of Australia and New Guinea, these red-finned blue-eye have been relocated 1,200km from a small group of springs fed by the Great Artesian Basin on Edgbaston Reserve in central western Queensland.
Evolution on the edge
As the only member of its family present in inland Australia, this fish has evolved in isolation for a very long time – as have most inhabitants of these springs – demonstrated to be the most ecologically diverse Great Artesian Basin spring complex in Australia.
Fish sampling at Edgbaston.
Here, in water as shallow as just 2cm, the only remaining wild populations of red-finned blue-eye survive. And it’s the most variable freshwater environment you can imagine.
Water temperatures can fluctuate 20 degrees in a day, and rise as high as 40 degrees in summer. Groundwater bubbling up through natural vents from the Great Artesian Basin is a constant 24 degrees and the tiny red-finned blue-eye occasionally huddle around the vents – presumably for temperature control.
A deadly rival
Long-term supporters will be familiar with the background to this story, as through freshwater ecologist Dr Adam Kereszy, we’ve trialled various methods of protecting the blue-eye on Edgbaston, where they’re threatened by the invasive mosquito fish (Gambusia holbrooki).
Gambusia are prolific breeders.
Introduced into Australia in the 1920s for malaria control, gambusia have become noxious pests with remarkable survival skills.
“To be honest, even without several million ‘gambos’ invading their habitat the blue-eye would still qualify as endangered simply because their range is so limited,” explains Adam. “But add in the most widespread invasive fish species in the world and the fact that each spring is its own ecological ‘island’, and the threat is far greater.”
Before starting our recovery project in 2009, we conducted an audit of the springs on Edgbaston and found 25 teeming with gambusia and only four with red-finned blue-eye. Critically, gambusia were absent from these four springs.
“When gambusia reach a spring with red-finned blue-eye, they eventually out-compete them,” says Dr Jim Radford, Bush Heritage’s Science and Research Manager and Chair of the Red-Finned Blue-Eye Recovery Team.
“We don’t know exactly how this occurs but we suspect it’s because gambusia give birth to live young whereas the blue-eye, like most fish lay eggs. So young gambusia are bigger, better equipped to fend for themselves, and may actually eat the eggs of the blue-eye and other fish. Without help the red-finned blue-eye’s future is bleak.”
Since purchasing Edgbaston in 2008, thanks to our supporters, Adam has tried physically removing gambusia from springs and constructed barriers to stop them migrating across the floodplain during overland flows. Approved trials using a chemical have successfully eradicated gambusia from selected springs without harming other inhabitants – including numerous species of snails, crustaceans and flatworms found nowhere else in the world.
It’s been slow work and while red-finned blue-eye have been successfully moved to four springs on Edgbaston, establishing a captive population as ‘insurance’ for the fish in the wild is a logical next step.
“We chose Sea Life Mooloolaba as a partner because of their enthusiasm for the project, their previous experience with captive breeding programs, and because they have specialists, such as Senior Aquarist Nick Henning, on staff,” says Jim.
Twenty fish made the journey to Mooloolaba and nearly six months on, the project is tracking well. According to Nick Henning, the fi have been observed ‘dancing’ and exhibiting signs of breeding.
At the time of writing we’re checking the tanks expectantly for eggs, which we hope will hatch into young. With luck and patience, one day we may see the grand‑children of the wild‑caught fish from Edgbaston.
In a spin – the fish’s mating dance
“Many fish engage in a type of dance before mating,” explains Nick Henning. “At least, it’s something between a dance and a fight.”
“When the red-finned blue-eye male becomes excited his colours brighten and intensify, and he’ll tail the female to encourage her to spin. If she’s receptive, she’ll join in spinning and eventually drop two or three eggs for him to fertilise.”
“A small spring can’t support a big population, so there’s no biological point dropping hundreds of eggs,” explains Dr Adam Kereszy. “They also need to be able to respond to rain and the opportunities it brings to migrate so they’re adapted to keep the population ticking over with two or three eggs a day.”
“Which makes captive populations tricky,” he concludes. “No mass spawnings and plenty of fiddly work for potentially a small number of healthy offspring. But we’re giving them every chance.”