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Carp caught and destroyed as government drains Isabella Pond precinct

Carp are the target of the ACT government's catch and destroy mission as teams work to drain Upper Stranger and Isabella ponds in Tuggeranong.

The introduced species, known to reduce water quality, will be eradicated from the two waterways before improvement and weir expansion works start as part of the joint Australian and ACT governments $80 million ACT Healthy Waterways Project.

ACT aquatic ecologist Matt Beitzel expected between 1000- 2000 carp would be captured from each pond, euthanised and turned into compost by a contractor. 

Using a large bobcat to create chanels for drainage and large sweeping nets teams hauled in fish, tennis balls, illegal yabby nets and even an broken empty personal safe. 

Mr Beitzel said Golden Perch and Murray Cod would be relocated if found through the process and once the works were complete and ponds naturally refilled the area would be re-stocked.

"This pond is being drained to eliminate carp but Isabella Pond will have wetlands built into it over the next 18 months," he said.

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"These ponds are open to fishing, obviously not while construction is happening, but we will restock them with fish people can fish for."

Waterwatch and Southern ACT Catchment Group ACT Indigenous Green Army volunteers assisted with the surveying 100 carp caught from the pond.

However they required a bit of help wrangling one of the heaviest caught, a female carp filled with eggs weighing 9 kilograms. 

Each fish was put into an anesthetic solution to be euthanised, then weighed, measured and decapitated so forensic analysis can be done on the fish's ear bone called an otolith.  

The tiny ear bone has rings like a tree which scientists analyse to determine age and life patterns. 

"When we extract it we can age the fish, see how long it has been in the pond, how quickly they grow so we can work out population dynamics," he said. 

"What we will end up with from these two lakes is a benchmark to measure the other lakes against in terms of total volume. That will help us if the carp herpes virus or biocontrol is released to plan for the clean up."

Environment directorate staff are due to drain Isabella Pond in the coming weeks and Mr Beitzel hoped the two waterways will soon be some of the territory's healthiest. 

"We'd hope these ponds remain carp free for a long time to come," he said. "That does depend a lot of the public not putting carp back in but moving fish around is illegal."