Final days to have your say before carp control recommendations released to govt

After that date, the Fisheries Research and Development Corporation will make its recommendations to the federal government on whether to release a herpes virus into the River Murray to control the pest fish.

Here's a summary of the findings of the seven research papers published in November.

The sight of all the dead fish will likely pose more of a risk to human wellbeing than the carp herpes virus itself, epidemiologist Katrina Roper and Laura Ford found.

After reviewing what little previous research existed, the pair found the human body was likely too hot for the virus, which only grew at temperatures between 18 and 28 degrees.

"There is a lack of high-quality evidence to support concerns about the potential for impact on humans," they said.

However, dead carp would need to be cleaned up quickly at sites highly visible to the public, and especially to children.

They also noted that the virus did not naturally have a 100 per cent kill rate, and that carp which survived were immune.

The widespread death of carp may present "considerable risks" to water quality, and human and environmental health, a team led by University of Adelaide Professor Justin D Brookes found.

Low oxygen, excessive ammonia and blue-green algae were all problems that would need to be managed.

By monitoring dead carp as they degraded, on scales ranging from a bucket to an entire wetland, the researchers developed a model for predicting when black water events and other problems would occur.

Water quality was likely to decline for a short time in areas with more than 300 kilograms of carp per hectare.

The team recommended flushing the river with extra water after the virus' release to wash as many nutrients as possible out to sea, preventing longer-term problems.

The SA stretch of the river is infested with more carp than almost any other part of the Murray-Darling Basin, researchers at Vic's Arthur Rylah Institute found.

The researchers divided the river system up into different habitat types; checked how many carp had been measured at sites of each type; built a model to predict how many carp there would be; returned to the real world to see if the predictions were accurate; then came up with a grand total.

"The lower Murray River in SA had some of the highest recorded biomass estimates, around 550kg/ha, reflective of the series of regulated, slow-flowing weir pools and permanent adjacent wetlands which provide optimal habitat for carp," the institute's report said.

If the drought broke, that number could reach as high as 4000kg/ha in areas below Lock One by 2023.

Across the basin there would likely be about 170,000t of carp by 2023 under drought conditions, or around 430,000t under flood conditions.

The Lower Lakes were one of two areas the researchers were not certain about.

Their model predicted there would be about 28,000 tonnes of carp in the lakes, where a 2010 study had estimated 1700t.

However, the institute's researchers were confident their estimate was more likely to be accurate.

Another study by Swiss researcher Claus Wedekind - famous for a study which used sweaty T-shirts to demonstrate women's ability to smell a genetically ideal mate - looked into alternative methods of carp control, such as sterilising all males or making females able to produce only male offspring.

He argued against using gene technology to wipe out the entire species, as such a treatment could conceivably spread to related species of fish.

But he concluded that, with more work and investment, an alternative to the herpes virus could be developed.

Brazilian expert Luiz Silva and his colleagues attempted to answer that question by reviewing 54 scientific and media articles about mass fish kill clean-ups around the world.

Dead fish were manually collected in almost 60pc of those instances, often using boats, nets and finally bins or plastic bags; the rest relied on predators or scavengers, trawling nets, earthmoving equipment or giant vacuums.

The number of carp to be cleaned up, the proximity of carp to towns, cost of the various options and destination for the dead fish - landfill or somewhere else - would all have to be considered as different plans were prepared for different areas.

Finding enough workers for the clean-up would also be important: "a major question is whether labour would expect payment or if communities would rally and offer volunteer labour".

The researchers strongly recommended conducting clean-up trials before releasing the virus.

They also suggested a hotline and/or app be made available to the public during any clean-up.

Liquid fertiliser, food for worms or fish, compost, meat and oil are among the products carp could be turned into.

"The composting methods developed during trials at Camperdown Composting are suggested as the most flexible and scalable option," a team from Curtin University recommended.

"The product value may be low but the process is likely to be able to use severely degraded product."

Fertiliser would be more valuable, a trial at Port Lincoln showed, but carp would have to be delivered to processing sites - of which there were few - within 72 hours.

The window for using carp meat would be even narrower: around 24 hours.

An attempt to separate carp into their solid and liquid components, and reuse the wastewater, was not successful.

They recommended the government feed more information about any clean-up strategy into a cost-benefit analysis, then identify locations where businesses might get involved.

The website at which the public can give feedback on the various studies will close on December 12.

Feedback must be entered into online forms for each individual report.