Drought and fire raise extinction risk in latest fish kills

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Angler and environmental advocate Matt Hansen surveys the Dubbo fish kill, along with his sons, Jack and Cooper. Image: ABC

INLAND angler Matt Hansen told ABC news a mass fish kill in the parched Macquarie River in New South Wales this week left the waterway looking like "tomato soup."

Thousands of fish have died in the latest Macquarie River fish kill near Dubbo, after rain washed sediment into the river, causing dissolved oxygen levels to drop rapidly.

Matt said he was staggered by the result.

"It looks like someone's tipped out a ute-load of mulch on the edge of the bank," Hansen told the ABC.

"It's actually dead shrimp.

"I've never seen the water like this — it's alarming to see.

"The river looks like tomato soup." he said.

While rain is the only thing that will break the drought, ecologists are warning fish deaths could occur in the Macquarie River with each new rain event, and could render multiple species locally extinct.

Professor Lee Baumgartner, a river management expert from Charles Sturt University, said silt can be deadly for fish during droughts.

"Run off from rainfall can quickly lead to deteriorating water quality and this, in turn, can have adverse impacts on aquatic biota," Dr Baumgartner said.

"In the Upper Lachlan in the 1920s there was a period of drought, then a bushfire, then a rain event which washed nutrient, ash and charcoal into the river," he said.

"Fishermen in the area said they never caught a Murray cod again after that."

Meanwhile, the southern purple-spotted gudgeon and the olive perchlet, two rare species that have not been seen for some time in the region, are at immediate risk of extinction, according to the NSW Department of Primary Industries (DPI).

DPI senior fisheries manager Sam Davis said efforts have been made to rescue the last-known populations of these two species from the Macquarie and relocate them to hatcheries until conditions improve.

"Our fish rescue strategy is not just about the big iconic fish that people love to catch and eat," Davis said.

"It's also about the small-bodied fish that fly under the radar which are equally vulnerable."

Other species at risk of extinction include the Oxleyan pygmy perch, Macquarie perch, silver perch and eel-tailed catfish.

Ms Davis described the threat of more mass deaths as "extremely concerning".

"Since European settlement our native fish stocks are estimated to have declined by 90 per cent," she said.

"So we're already starting from low numbers."

Source: ABC

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