Carp frenzy following floods has irrigators looking for solutions

The large presence of carp in the river has greatly affected SA water quality and has affected many irrigators and landowners pumping systems.

SA Murray Irrigators chair Caren Martin said the large carp numbers had resulted in a number of problems, such as the clogging up of filters.

"They create turbidity in the water itself, so you get a lot of collodial material and mud and grit and bits etc," she said.

"That affects our filters and the algaes and all the bits that go through that, but also our water quality when it actually gets into our dams and out our pumps on the other side."

Ms Martin said the filtration process could be extensive when carp were found in pumps.

"Not only expensive, it takes a little bit of water and just time," she said.

"So you're doing it more often and therefore, you're not getting on with the business of farming the other things."

Ms Martin said there had been some failings in dealing with the reduction of carp numbers.

"I believe it was a missed opportunity in the millennium drought to actually combat what then would've been low numbers and, given they're a European species, they were all up in the backwaters sitting in the billabongs and the lagoons," she said.

"It was a great opportunity to physically remove them when they were stranded and then the flood waters came through, pushed the adults out into the channel and they bred."

Ms Martin said the state and federal government needed to have taken action against the high carp population a long time ago.

"Communities were telling them and we were all told, no because the savior was the herpes virus," she said.

"It's a classic example of the government, putting so much investment into one option that they have no other option but to go with it."

There were a number of strategies that must be explored, such as carp catch cages to combat the large number of carp, Ms Martin said.

"I think they're going to have to keep trying all of the above and invest in all of them," she said.

"Get a diversity of projects going, that would be nice."

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A PIRSA spokesperson said the National Control Carp Plan was funded by the Australian government in November, led by the Fisheries Research and Development Corporation, to assess the use of Cyprinid herpes virus 3 (the carp virus) as a biological control agent for reducing the impacts of carp.

They said the state government, Australian jurisdictions and several national committees would review various aspects of the plan before deciding to begin the biological control program.

"Technical papers accompanying the NCCP cover a range of topics, including understanding whether the carp virus could impact on other species, understanding how effective the virus could be, social implications and views on releasing the virus," the spokesperson said.

Other methods to control the high percentage of carp have been explored, but aren't believed to be as effective, they said.

"The alternatives have typically had limited effectiveness, highlighting the importance of a national approach, carp exclusion screens and jumping traps have been trialed in SA," the spokesperson said.

"These devices aim to limit carp access to spawning habitat, or capture jumping carp as they migrate."

The spokesperson said while carp fishing events had been held, they would not prevent the births of more carp.

They said commercial harvesting occurred in the River Murray, but was extremely labor intensive and had limited effectiveness in reducing the abundance of carp.

"Community-led carp fishing events are held along the River Murray and are successful in attracting a large number of participants," the spokesperson said.

"However, excluding or removing a proportion of adult fish from the population doesn't prevent carp from spawning and replacing the harvested fish."

The spokesperson said before the carp virus was released, further research, specific regulatory approvals, significant planning for implementation and extensive community consultation must be undertaken.