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Fish numbers ‘reasonable’

Thursday, 20th June, 2019

The devastation after hundreds of thousands of fish perished in the Darling River over summer. The devastation after hundreds of thousands of fish perished in the Darling River over summer.

By Craig Brealey

Native fish are being found in “reasonable numbers” just below Weir 32 where millions of them perished in December and January, according to the Department of Fisheries. 

The fish are being caught and tested this week by NSW Department of Primary Industries - Fisheries to determine how the population was affected by the catastrophe.

The sampling is being done at two sites immediately downstream of Weir 32 and next week the fisheries scientists will go to a site upstream of the Pooncarie weir and test the fish there for comparison, said Cameron Lay, the program’s leader and Assistant Director of Aquatic Environmment, NSW DPI Fisheries.

Mr Lay said two methods were being used to catch the fish - electro-fishing and traps - and the fish were then released back into the river.

With the former, an electrical current is put into the water from a boat which stuns the fish and they float to the surface where they are collected.

Trap baits and opera house traps are being used to catch the smaller fish.

“The fish are counted and measured, and a tissue sample is taken for the lipid, or fat, content and this gives you an indication of the health of the individual fish,” said Mr Lay.

“I don’t yet have a breakdown of the species being caught, but it seems there are still a reasonable number of native fish, which is a positive thing.

“We didn’t see many carp in the fish kills so there was concern that they might have come to dominate but the numbers of native fish is a positive sign.”

Mr Lay said an interim report on their findings will be published next month and a more comprehensive report later in the year.

The work is being done with funding support from the Murray-Darling Basin Authority. 

The mass fish kill of Murray Cod, perch and bony bream was attributed by a panel of scientists to the drought, extremely hot temperatures followed by a cooler snap, and excessive extraction by irrigators upstream.

Acting Deputy Director General DPI Fisheries, Sarah Fairfull, said there was still too little water in the system but the quality had improved during the winter.

“The most recent dissolved oxygen data from within the Menindee Weir 32 weir pool (the affected reach) and surrounding Lower Darling shows that levels have returned to normal and the water in the pools is well mixed,” Ms Fairfull said in a statement.

This had made the catching and testing less stressful to the fish, she said.

“This critical research will allow us to determine the extent of the impact from the fish kill events, report an estimate on the number of fish that survived and their current condition, and guide management actions in the region to protect and recover native fish populations,” Ms Fairfull said.

“More than 500 kilometres of the Lower Darling was unaffected by these fish kill events, which provides DPI Fisheries scientists with the ability to compare populations and to support the restoration of the affected reach.”

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