Toolondo threat from infestation

Toolondo Reservoir south of Horsham looms as a potential test water for the release of a carp-specific virus, with research revealing it has a growing infestation of the pest species.

Catchment authority leader David Brennan said ‘disappointing’ water samples had revealed the lake’s carp population had spread across the lake and would now be difficult to control.

“EDNA sampling results have shown the carp are not simply congregating in isolated areas where we might have been able to target them with electro-fishing,” he said.

“The evidence we’ve received is that they are widespread.”

Mr Brennan added the fear now was the carp would become the dominant fish and largest biomass in the lake and the proposed release of a virus, depending on safety checks, might be timely.

“It’s very disappointing. It has clearly identified that carp have heavily infiltrated the lake and as a primary recreational water with significant historical and environmental value it might be an ideal target for a virus release,” he said.

“In other words, it might be a case of ‘the sooner we get the carp virus the better’.

“We’re talking about a high-potential lake – one of the best fishing and sightseeing lakes in Victoria that hasn’t had a lengthy history of carp invasion.

“Who knows? We might be able to stop it in its tracks.”

Wimmera Catchment Management Authority collected nine samples from Toolondo’s three primary wetlands for EDNA analysis in response to reports of growing carp catches from the lake.

EDNA technology involves identifying cells present in water samples to assess levels and types of aquatic life in a waterway.

Mr Brennan said the research had shown the lake had a range of carp age groups.

“The indications are the carp have been in there a while,” he said.

“There are fish in there weighing up to 10 pounds to fish that have only bred in the past 12 to 18 months.

“Environmental conditions, with Toolondo being a large lake with shallow areas, are also suitable for the population to significantly increase.

“We’re in discussions with Fisheries Victoria about what options and techniques that could be deployed to help control the carp, but this won’t be any easy fix. As it stands now, electro-fishing would not be an effective control method.”

The catchment management authority has suggested the Wimmera River system, that includes Toolondo, might be ideal as a virus-release site as part of a National Carp Control Plan.

The future of Toolondo Reservoir, with a reputation as one of the best trophy-trout fishing lakes in Australia, has been the subject of considerable debate.

The State Government has been directly involved in projects to protect its sustainability as a recreational fishery.

Water has been flowing into Toolondo from Rocklands Reservoir as part of a water-management schedule.