Hardy little fish is struggling
The Murray hardyhead.
A tough little fish that looks like a golden sardine has been saved from possible extinction in the drought-stricken Murray-Darling system by an ecologist at the University’s Mildura campus. Iain Ellis has raised two generations of the Murray hardyhead – Craterocephalus fluviatilis – from egg to adult in tanks at his research centre.
‘It’s a unique species,’ he says, ‘one of a few salt tolerant fish in the Murray-Darling system.’ He believes ancestors of the fish may have survived cycles in weather fluctuations and flood regimes since the Murray-Darling was part of a vast inland sea.
A unique ability to withstand high concentrations of salt has allowed the species to survive while most other small fish have perished.
‘In the boom-bust environment of the Murray-Darling it has managed to find a refuge niche,’ says Mr Ellis. ‘Yet, despite really good survival strategy, it’s now struggling due to regulation of the river system and the ongoing drought.’
Originally, the fish would have occupied hundreds of wetlands. River regulation in the 1900’s meant most wetlands have either dried up or become permanently filled.
‘Like desert kangaroos, the Malle fowl – and even Mallee farmers – the Murray hardyhead is sturdy, tough and adapted to the semi-arid environment,’ Mr Ellis says.
Late last year, the keen fish ecologist trapped about 200 samples of the fish in rapidly-drying Lake Hawthorn, relocating them to the Mildura campus nearby. Only two lakes in Victoria, near Swan Hill and one small wetland near Mildura, now support the fish – and these have all required topping up with environmental water.
Mr Ellis is now campaigning for the fish to be moved from the ‘threatened’ to ‘critically endangered’ list. This will help conserve the fish and their natural habitat. In the meantime it is breeding well on campus.
The fish reach up to eight centimetres in length and are strongly associated with a salt-tolerant plant called Ruppia that looks a bit like bird feathers. They hide amongst its fronds, eat bugs attracted by the plant, and their eggs adhere to the leaves.
The first captive-born fish began breeding recently and the population appears to be free of diseases and in good genetic health. They have a short breeding cycle and live for only 18 months in the wild, which makes them vulnerable to extinction in times of low river flows and drought.