WATER quality in the ACT is set to improve after more than 5 tonnes of carp were recently removed from some of Canberra’s largest ponds.
According to an article in the Canberra Times, more than 2200 of the introduced species were captured during the ACT Government’s catch and destroy mission at the Upper Stranger and Isabella ponds in Tuggeranong.
The findings of the mission, which took place in April as part of the $80 million ACT Healthy Waterways Project, were unveiled at an ACT conservation seminar this week.
Aquatic ecologist Matt Beitzel said the introduced species have been known to be a major pest in many Australian waterways.
“They are an intrusive species and highly predatory and also eat juvenile fish and harbour diseases,” he said.
“They rumble through the sediments and stir it up, meaning it never solidifies and water weeds cannot grow there.”
As part of the carp cull, other introduced species such as red fin and gold fish were also removed from the Tuggeranong waterways.
An estimated 1510 carp, or 2.59 tonnes, were removed from the Upper Stranger Pond, with 765 carp, or 2.5 tonnes, were taken out of Isabella Pond.
Mr Beitzel said the carp made up almost 85% of all the biomass in the ecosystem.
“They’re the largest animal in the system and make up a very large portion of the biomass, taking things away from the environment,” he said.
While the ponds were being drained to eliminate the carp, it also allowed for the construction of a weir to allow for nearby wetlands to be built into the environment.
Mr Beitzel said a variety of ways were used to remove the carp from the waterways, including some by hand.
Because of the sediment in the pond, we had to come up with different methods to get them out,” he said.
“One of the methods was using a small aluminium boat on a rope and pulling it across the water using manpower and hand netted each of the fish into the boat.”
With the removal of the introduced species, it’s hoped native fish such as Murray cod and golden perch will be able to flourish.
Several thousand of the native species will be stocked in both waterways in coming months, with almost 3000 set for Upper Stranger Pond later this year, and more than 5000 for Isabella Pond once it is refilled in 2018.
“Hopefully the removal of carp, along with the building of wetlands will result in a clearer water supply and cleaner water for those ponds,” Mr Beitzel said.