The red-finned blue-eye, once considered Australia’s rarest freshwater fish, has seen a significant increase in its population over the past eight years.

From a mere 1,000, their numbers have risen to 5,000, prompting Queensland to designate their habitat as a special wildlife reserve.

Previously, the species was nearly driven to extinction by the invasive gambusia, also known as mosquitofish, which is larger and more aggressive. These invasive fish had restricted the red-finned blue-eye to a single artesian spring in outback Queensland, making the situation extremely critical.

“It got very, very dire,” Bush Heritage Australia ecologist Dr Dean Gilligan says.

In an effort to save the species, conservationists reintroduced the red-finned blue-eye to 13 additional shallow springs within the Edgbaston Reserve. This former cattle station, located about 1,000 kilometres west of Brisbane, is unique for hosting 26 species found nowhere else in the world, including the red-finned blue-eye.

The springs, which provide a desert sanctuary with artesian water, are protected by foot-high shade cloth fences designed to keep the gambusia out and preserve native fish populations.

However, environmental management efforts led to the springs doubling in size, causing about a quarter of the fences to be breached. This increase in spring size was due to a government bore capping scheme aimed at revitalising the Great Artesian Basin aquifers.

“It’s a poison chalice,” Gilligan says. “The extra spring flow increases the size of springs that native fish and other spring fauna and flora can occupy, but it makes managing the threat much more difficult.” Three years of flooding due to above average rainfall hasn’t helped either, he adds.

As water began seeping beyond the fence lines, opportunistic crabs and yabbies created pathways for the gambusia to invade. Once inside, the gambusia wreak havoc by attacking the fins of native fish and consuming their eggs and larvae. Introduced to Australia in 1929 to control mosquitoes, gambusia have become a declared noxious pest.

“It’s a prison escape, but they are trying to get into the prison, not out,” he says.

It’s put conservation efforts on the reserve in “uncharted territory”, Gilligan says. “We don’t know how much bigger those springs are going to grow.”

To address these breaches, ecologists undertake a meticulous process: they capture and relocate the surviving native fish to heated holding tanks, use vegetable derris dust to poison the gambusia, reinforce the fences, drain the springs, wait for them to refill, and finally reintroduce the native species.

“They’re bullies” says Dr Renee Rossini, a Bush Heritage freshwater and wetlands ecologist.

While this process can take weeks for small springs, it may take over a year for larger interconnected pools.

However involved the process, Rossini says it’s critical to saving a species that “helps us understand how life functions, how diversity is created, how our world has changed”.

Bush Heritage Australia, which purchased Edgbaston in 2008, plays a crucial role in maintaining the ecosystem to protect its unique species. This conservation effort led to the Queensland government’s recent decision to declare the land a special wildlife reserve. This designation offers the same protections as a national park, banning petroleum and mineral resource extraction indefinitely.

This special wildlife reserve status is part of legislation introduced in 2020 to better protect private lands with exceptional natural and cultural value, making Queensland the only state in Australia to offer such high-level protection.

The agreement will “ensure this estate will remain a site of international environmental significance well into the future,” Linard says.

Environment Minister Leanne Linard highlights this unique initiative, and Bush Heritage Australia aims to extend similar protections to four more of its conservation areas in Queensland.

Bidjara traditional owner, Trevor Robinson, endorsed Bush Heritage’s protection. “The land is part of Bidjara culture, our connection to country, place, storylines, language and social practices,” he says. “It’s a place that is extremely special.”

Despite the remarkable increase to over 5,000 red-finned blue-eyes, Dr. Gilligan warns that without ongoing conservation management, their numbers could rapidly decline within a few seasons, underscoring the importance of continued efforts to preserve this rare species.

“It’s a constant battle, we don’t know the answers, we are trying the best we can and hopefully we’ll stumble on a solution,” Gilligan says.

“We’ll just keep fighting the fight.”

 

 

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