You may have heard about our recent rescue of the Dargo Galaxias – a native fish named for its home - the Dargo River near Mt Hotham. It’s the only place on the planet where this fish exists in the wild.

Earlier this month, 200 of these small native fish (they’re about the size of your middle finger) were captured and transported to tanks at our Arthur Rylah Institute for Environmental Research (ARI) in Heidelberg. It’s an insurance policy against potential extinction.

So why do fish like the Dargo Galaxias need protection from bushfires?

Dr Tarmo Raadik, a Senior Fish Ecologist at ARI explains: ‘Heavy rainfall after intense bushfires, like those experienced in East Gippsland, is potentially deadly for aquatic animals,’ he says. ‘The rainfall picks up soil, rocks and timbers burnt during the fires and deposits them in waterways, which can bury fish; a little like what happened in Pompeii 2,000 years ago.

‘When we have really intense fires, as we have this summer, it changes the soil’s structure, so it doesn’t absorb the water but is carried along with it.

‘You can get tonnes of this sediment blanketing entire streams, with aquatic animals in small waterways at greatest risk.
‘Even if the fish aren’t buried completely, the debris that ends up in the river or stream can absorb the oxygen in the water or block the fish’s gills, suffocating them.’

The Dargo Galaxias were captured using electrofishing. ‘It sounds dangerous but it’s a very effective and sensitive way to collect the fish without harming them.

‘We lightly stun the fish, then collect them in buckets within a few minutes.’

If the worst happens in the wild, the captive fish can be used to repopulate once the waterways are deemed safe again.

The 200 captive galaxias are now enjoying their temporary home in the ARI tanks (Tarmo compares it to a health farm for fish).
‘Looking after these galaxias is a lot more complicated than having a pet goldfish. They live in very chilly waters, so the tanks must be cold.

‘The water quality must be perfect as well.

‘It’s a bit like looking after a baby or providing the kind of life support an astronaut in outer space would need.’

Adding to the complexity of their care, the Dargo Galaxias don’t have any scales, making them vulnerable to abrasions and fungus, particularly in captivity.

The fish will be returned to the Dargo as soon as it is safe to do so, but it’s likely to be at least four months before they’re home in the wild again.

‘The timing of their return depends on the rainfall in the area, how the vegetation near the streams recovers and whether we have other issues like algae to deal with.’

Similar extractions are also being considered to prevent the extinction of other threatened species of galaxiids, freshwater crayfish and mussels in the face of this summer’s bushfires.

Page last updated: 27/07/20