Time to pull the plug on carp

National Carp Control PlanIn the first week of April 2017, a carp eradication program began upstream of Lake Tuggeranong...

It’s dirty, smelly, tough work but the ecologists removing carp from Upper Stranger Pond in Monash had big wide grins on their faces.

“This is a rare opportunity to collect carp and conduct some valuable research,” said aquatic ecologist, Matt Beitzel, thigh deep in the mud and sediment that was left behind after the pond was drained.

Estimates suggest that the pond contains up to 2,000 carp, with some over nine kilograms. Once the fish were euthanised, a team of volunteers from The Green Army and the Park Carers of Southern Murrumbidgee, weighed and measured the fish and removed 100 heads for further research.

“Later in the lab the ear bone (or ‘otolith’) will be examined to determine lots of things, including the age of the fish. This type of life cycle information is really important to our understanding and management of carp,” said Matt.

Carp is an invasive pest species introduced into Australia more than a century ago and now widespread throughout the Murray-Darling Basin. Highly adaptable and with destructive feeding habits, carp have a detrimental effect on native aquatic plants, animals and general river health.

Upper Stranger Pond and its bigger neighbour, Isabella Pond, had to be drained in order to conduct major works on the weir and to build two new wetlands. The draining presented an opportunity not just to remove and study the carp but also to test the methodology behind estimating carp populations in waterways.

“Any future eradication plan will rely heavily on being able to accurately estimate the numbers – not just in terms of choosing the right approach but also in managing the clean-up,” explained Matt.

When the carp are gone and water returns to Upper Stranger Pond, it will be re-stocked with native fish. Isabella Pond will remain empty while the weir is widened and the wetlands are constructed.

The twin wetlands in Isabella Pond are one of three projects planned for the ponds as part of ACT Healthy Waterways, a joint Australian and ACT government initiative to build water quality infrastructure on up to 25 sites around the ACT. Later in the year work will begin on the naturalisation of a concrete channel feeding Isabella Pond and a rain garden beside Upper Stranger Pond.

The three infrastructure projects, combined with the carp eradication program, will help to improve water quality in the ponds, in Lake Tuggeranong, downstream in the Murrumbidgee River system and in the wider Murray-Darling Basin.