Hundreds of dead fish have been found on the banks of several central Queensland waterways, but authorities say there could be a simple explanation behind the deadly occurrence.
About 350 to 400 dead barramundi have been found at Callide Dam, just outside Biloela.
Colin Bendall, the executive general manager for Sunwater — the government organisation that operates the dam — said the dead fish were large, about 10 kilograms and 1.2 metres in size.
"We have seen increased numbers over the past week," he said.
"Most of those are introduced barramundi."
About 100 dead barramundis have also been found in the past month at Lake Awoonga, near Gladstone.
Cause of fish deaths
Darren Barlow from the Gladstone Area Water Board said those fish were showing signs of a seasonal fungal infection, likely caused by adverse weather conditions.
"Conditions such as unseasonal winter rain, prolonged strong westerly winds, and limited access to warm water bays due to current lake levels can all impact fish health," Mr Barlow said.
"While there is potential for more fish death sightings at Lake Awoonga, don't be alarmed if you find a sick or dead fish.
"This event is rare … [but] similar events have occurred at Lake Awoonga and many other impoundments in the past."
Mr Bendall said it was too early to tell whether the fish in the Callide Dam had also been impacted by a fungal infection.
But across winter, a minimum of minus 0.5 degrees Celsius and a maximum of 21.5 degrees have been recorded at Callide Dam.
The changes in temperatures are believed to have played a part in those deaths.
"Our main concern is making sure we get the fish cleaned up as soon as possible … as obviously it's quite concerning for locals visiting the dam and also the fish stock society," he said.
He said the incident had not impacted water quality from the dam, which provided drinking water to Biloela.
"We take regular samples of the water quality, and we're also working closely with the local council," Mr Bendall said.
Fishers and recreational users at both dams have been urged not to touch the dead fish due to the risk of injury or potential infection.
A spokesperson from Queensland's Department of Environment and Science said it was aware of both incidents and was monitoring for further reports.
"Members of the public can report fish deaths to the department's pollution hotline on 1300 130 372," the spokesperson said.
