Staff at Narrandera Fisheries Centre played a key role in the race against time to save Murray Cod and perch from dying in a water-starved Darling River.
NSW Department of Primary Industries made the decision to proceed on Thursday with the relocation of the cod in the wake of WaterNSW stopping flows from Weir 32 to maintain Menindee’s water supply. This would leave the Murray Cod ever more susceptible to stress from low levels of dissolved oxygen.
Yesterday, DPI staff returned to the weir and two shallow isolated pools downstream to rescue golden and silver perch.
A total of 20 cod, measuring from 80-100cm and estimated 10 to 20 years of age, were scooped out in nets by DPI Fisheries staff and placed in specialised transport with aerated and temperature monitored tanks. They were trucked to Narrandera Fisheries Centre to regain their health for future breeding and restocking purposes to directly benefit the native fish community of the Lower Darling river.
It is expected the cod will have a productive potential of more than 100,000 fingerlings a year.
Narrandera Fisheries Centre assistant hatchery manager Lachie Jess prepared the tanks for the arrival of the fish on Thursday evening. Mr Jess said the fish were resting comfortably in a salt bath to relax them and treat any parasites.
“They will spend two weeks in quarantine before being introduced to our brood stock ponds,’’ he said. “They won’t be disturbed and will be given the opportunity to spawn and breed in those ponds.’’
Mr Jess said the fish had not been sexed but once removed from the salt baths, they would be weighed, measured, tagged and sexed. He said the fish were stressed but had travelled well and settled in quickly at Narrandera.
“They were in a position where they were under some threat,’’ Mr Jess said. “There was a trickle of water running through the weir, giving them enough fresh water to survive in, and they were taken out of that pool, arriving here at 7pm.
“They are in the best care and are certainly much safer here now.
“Narrandera Fisheries Centre is important for this sort of operation and now the fish are back on site they have the best chance to go ahead and breed.’’
Mr Jess anticipates more calls to save native brood fish as river levels continue to fall.
“It’s going to be an on-going issue with the drought and lack of water across the state and basin,’’ he said. “We will play it by ear and see how we can go.’’
The silver perch, a listed threatened species, and golden perch would also be used as broodstock at Narrandera Fisheries Centre, with fingerlings returned to the Lower Darling as part of native fish recovery efforts when conditions improve.
Narrandera Fisheries Centre manager Martin Asmus said fish rescues were not new to the station’s staff.
“The last drought was typified by rescues of small bodied native fish such as pygmy perch and Macquarie perch, which were bought back here to safeguard those populations. They are even more fragmented and vulnerable to loss as the fish kills aren’t as visual as the large bodied fish.’’
Mr Asmus said the rescued cod were imprinted to the Lower Darling system and would enhance the river with their fingerlings once river levels return.
“All is not lost,’’ he said.
Generally, relocating fish is not a preferred solution due to the additional stress it places on already stressed fish, but fisheries experts from DPI are prepared to do whatever they can to help the state’s native fish during these exceptional circumstances.
In addition to the fish rescue, DPI is continuing to monitor water quality and is finalising an assessment of temporary aerators placed within the Darling River to provide localised water quality benefits and fish refuge. DPI remains on alert for fish deaths in the Lower Darling and a number of other high risk sites and is continuing to monitor these locations.