Positive spin will be the National Carp Control Plan's number-one weapon if a virus targeting the pest fish is released into the River Murray.
An NCCP issues paper has outlined the problems which could accompany the carp virus release proposed by the federal government: the sight and smell of dead fish, poor water quality, restricted access to riverfront areas and "fear or distress" among local residents.
Murray Bridge and the Coorong and Alexandrina districts were likely to be among those most affected, the paper said.
A decrease in tourist numbers of "likely to be no greater than a third, and likely smaller" was to be expected around the time of the virus' release, and could be worse in the event of large-scale fish kills or water quality issues, the NCCP said.
Positive messaging and clear communication would be needed to reduce the impact of any downturn.
Governments would likely need to bail out tourism operators if any virus-related disruption lasted longer than a month or two.
However, there was potential for tourism growth in the long term.
Every local council, irrigator and farmer the NCCP had spoken to felt the risks of a virus release could be managed, the organisation said.
The proportion of people in favour of a carp virus had remained steady at about 50 per cent since 2016, the NCCP found, while about a third were undecided, though both figures would be susceptible to change if more information became available.
Almost two thirds of people worried about the impact a virus would have on water quality, and almost 60 per cent worried that cleaning up all the dead carp would be impossible or that the virus would have unintended effects.
Previous research finding the virus could not be transmitted to other species, including humans, had done nothing to calm fears held by about 50pc of the population.
The issues paper also recommended the government focus not just on removing carp, but on projects that would lead to better fishing, clearer water and greener river banks.
Removing carp will not solve all river's problems
The NCCP also published two other reports last month.
University of Canberra freshwater scientist Susan Nichols and a research team found that getting rid of carp alone would not fix the Murray-Darling Basin's ecosystem.
A survey of environmental experts concluded that removing at least 70 per cent of carp from the river system, and keeping the species' population down, would have a positive impact over 5-10 years.
The Murray's water would become clearer and there would be fewer nutrients in the water and more aquatic plants, yabbies and insects, especially in wetlands.
Without a plan to control carp, the system would keep getting worse.
But getting rid of the pest fish was not the be-all and end-all, Dr Nichols and her team said.
"Without other, non-carp mitigation actions to address the widespread environmental problems, (experts') confidence was not high that ecosystems could recover," they said.
"Degraded systems may not return to their original state after the reduction of carp.
"Complementary actions are considered necessary to facilitate long-term ecological benefits."
There were risks that the environment would recover more slowly than it had got worse, and that other non-native species such as redfin would simply fill the gap in the food chain vacated by carp, they said.
A second study, by La Trobe University Associate Professor Paul Brown and his colleagues, reinforced earlier NCCP suggestions that no amount of fishing was likely to fix the carp problem.
The use of commercial fishing to reduce a population of fish was more effective in small, closed waterways, Professor Brown and his team said.
In complex systems like the Murray-Darling Basin, other measures would also have to be used.
In reaching the conclusion, researchers looked at examples from around the world and plugged the numbers they had into a software package called CarpSim.
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