“N Nature 2.0
o two springs are the same. They all have their individual quirks,” says ecologist Rob Wager, as he casts about for signs of Australia’s smallest freshwater fish.
It is just before dawn at Edgbaston Reserve, centralwestern Queensland, and Wager is standing barefoot and ankle-deep in a small fenced area known as Type Locality Spring. It’s here that the first officially described specimen of red-finned blue-eye (Scaturiginichthys vermeilipinnis) was collected in 1990. The air is alive with the mewling and scraping of frogs, and as the sun crests the horizon it catches in the native grasses of the wetland’s sodden soils.
Scientists estimate that the water bubbling up at Type Locality Spring is completing a two-million-year cycle through the Great Artesian Basin. This “dinosaur water” emerges at the spring’s head at a balmy 24 degrees Celsius, year round. Beyond the spring’s head lies its tail, which can wag its way across the flat, dry landscape over weeks, months or decades, in response to a complex interplay of variables that even freshwater ecologists struggle to explain.
In 2008, Bush Heritage Australia purchased Edgbaston Reserve, a former grazing property, to protect the site’s springs, vegetation and the myriad animal species that call this country home. Of particular concern is the critically endangered red-finned blue-eye, as its habitat now covers less than half a hectare of the shallow water pooled beneath mint-green saltbushes and prickly spinifex clumps.
These fish, which grow to a length of no more than 3 centimetres, favour springs that are shallower than 80 millimetres. Type Locality Spring is between 20 and 50 millimetres deep, and this produces dramatic fluctuations in water temperature. “At the margins [it] might change up to 21 degrees Celsius over a day,” says Wager, “which is quite a lot for a fish.” But the little fish have evolved to deal with these challenges. “They’re very tolerant.”
If left unmolested, adult blue-eyes will cluster around the spring’s head, where the temperature is constant. However, that option is becoming increasingly unavailable. The resilience of the blue-eyes is being tested by an influx of the eastern gambusia (Gambusia holbrooki), an invasive fish native to the United States. Also known as plague minnows,
gambusia were introduced to Australia in the 1920s in an unsuccessful attempt to control mosquitoes. Relatively small but aggressive, they spread rapidly, both through deliberate introduction and by unhappy accident, washed by storm and flood into new waterways. The finger-length gambusia are omnivorous and opportunistic, gorging on anything small enough to fit in their mouths. They also bear live young (a rare trait in fish), giving them an edge over many of their competitors. While pigs and other feral animals can severely damage blue-eye habitat, “gambusia are the problem”, says Wager. “They’re the number one threat. Nothing else comes close.”
Of the seven springs known to have held red-finned blue-eye populations in the 1990s, Type Locality Spring is the only one that remains gambusia-free. It’s this rapid loss of safe spaces for native fish that has led Bush Heritage to trial an ambitious program of spring rehabilitation.
The next spring is one of the property’s “renovated” habitats. It was full of gambusia a year ago, and in poor condition due to previous modifications to make it more accessible to stock. “We like nature to fix itself if it possibly can,” says Wager. “We’d written this spring off for redfinned blue-eyes.” Often, the only way to effectively remove gambusia from springs is to poison them, which Wager and his team are loath to do as the process also kills native fish. But at this site the team was able to trial a new technique, corralling the pest fish and scooping them out. Six months later, once Wager was sure the gambusia were gone, he introduced 50 adult red-finned blue-eyes from Type Locality Spring.
Darting about in the shallow water are the “teenagers”, as Wager calls them, only 4 to 5 millimetres long and no more than a couple of weeks old. Wager estimates that blueeyes begin breeding when only a few months old, at which time the males’ fins brighten to a handsome red and they engage the females in a spinning dance, urging them to drop eggs to be fertilised as they sink to the sediment below. Their breeding capacity tails off from around eight months, and is effectively over by their first and only birthday. That’s not a lot of time to reproduce and shore up the fate of your species, which is why it’s so important that the blue-eyes are given space to breed without interruption.
This cleansed spring is bordered by striped shade cloth, which gives the site a beachy feel. The cloth edge is buried into the surrounding soil to keep animals from digging under it, and is pegged up to a height of about 50 centimetres, blocking access to any gambusia that might be swept into the spring by overland flows.
“It’s really perilous,” says Wager. On the other side of the flimsy-looking barrier is another shallow spring writhing with hundreds, if not thousands, of gambusia. There are some concerns that isolating small populations of blueeyes may lead to inbreeding, but with gambusia so close by, opening up the spring is not an option.
Tom Sjolund, a long-time Bush Heritage volunteer and the reserve’s resident techie, helps Wager install a small waterproof camera not far from the spring’s head, and everyone clusters around a laptop in the back of the four-wheel drive to view what’s happening beneath the water. One of the reserve’s six endemic snails shuffles into view, and other indistinct shapes flit past. Not only does Sjolund’s set-up help with studying these tiny fish in their native habitat, it’s hoped it will also provide a heads-up should gambusia breach this key stronghold. Elsewhere, scientists are working to breed non-reproductive gambusia, which could be released into feral populations to effectively sterilise them. But the science is not proceeding quickly enough.
To give these native fish a fighting chance, Bush Heritage has also set up a breeding program at the Sea Life Sunshine Coast aquarium, where an insurance population of blue-eyes is kept and studied. But life in a tank is not life in the wild, which has prompted Wager and the team to try something completely new.
Next to Edgbaston’s old shearing shed (which Bush Heritage has converted into its field camp HQ ), Wager has been overseeing the creation of artificial springs, carefully designed to mimic the blue-eyes’ natural habitat. The area is enclosed by raised bunds of earth and more shade cloth. Inside the enclosure, artificial springheads are being created within buried round plastic cow troughs with holes cut into their sides. “We’re trying to emulate the deep heads of the springs,” says Wager. The springheads will be drip-fed water from a bore. Outside the enclosed area are two huge tanks propped up on sturdy metal frames. “If the bore stops for whatever reason, the tanks will give us two weeks’ grace.”
The first artificial spring is filling with water, and volunteers are busy planting it out with species transplanted from the drying tail of a nearby spring that “changed its mind”. Over time, they’ll translocate a variety of macroinvertebrates, including local shrimp, which should help keep algae growth under control. And, of course, they’ll introduce the blue-eyes.
As the impact of climate change, invasive species and habitat loss continues, projects such as this will become increasingly necessary to stop threatened species from sliding into extinction. And in places like Edgbaston, where native ecosystems are collapsing faster than they can be rebuilt, until some sort of equilibrium can be found, these habitat simulacra might just be even better than the real thing.