Scientists Find Simple Fix for 100-Million-Year-Old Fish

A fish that predates dinosaurs is finally getting a second chance at survival, thanks to a researcher who learned to outsmart one of nature's hungriest creatures.

Australian lungfish have lived virtually unchanged for over 100 million years, making them the closest living fish relative to humans. These remarkable animals can breathe air through a unique single lung and live up to 90 years in the wild, possibly over 100 in captivity.

But in Brisbane River, they faced an unexpected problem. When Wivenhoe Dam was built 40 years ago, it accidentally disrupted the lifecycle of Vallisneria, an aquatic plant the lungfish desperately need. The fish hide their eggs in these underwater meadows for three weeks, and newly hatched babies shelter there for six months.

After devastating floods in 2011 scoured the plants from the riverbed, researchers expected them to bounce back naturally. In nearby rivers without dams, the plants typically recover within three years as seeds and fragments float downstream and take root.

The dam blocked this natural recovery. Scientists tried growing Vallisneria in fenced enclosures downstream, but the torpedo-shaped lungfish broke through every barrier to feast on the cultivated plants.

During one flood event, researcher David Roberts from Seqwater said lungfish were so thick in the enclosures that scientists were tripping over them. They demolished the entire habitat, joined by turtles and invasive fish species in a feeding frenzy.

The Bright Side

PhD candidate Colin Burke from Griffith University tried something different last summer. Instead of creating one large buffet the fish could circle and devour, he scattered small clumps of plants across five shallow spots along a 1.5-kilometer stretch of river.

The strategy worked beautifully. Tiny beds of Vallisneria are now establishing along the riverbank, spreading out faster than the hungry fish can eat them. Burke also drove stakes into the river, giving the plants more places to catch and grow.

"When you see the little plants pop up, it's quite exciting to be honest," Burke said. He believes this is the first time anyone has restored aquatic plants using this method, and he's planning to expand the experiment further downstream.

The approach is cheaper, less labor-intensive, and far more effective than the elaborate fencing systems. By working with the lungfish's appetite rather than against it, Burke created a sustainable path forward for one of Earth's oldest living species.

For a fish that's survived 100 million years, hope is finally flowing downstream again.