June 16, 2017
By Jonathan Wright
If you've fallen into the recently trendy habit of kissing your catch before release, you might want to think twice about doing it in Australia. A government sanctioned release of a herpes virus specifically designed to only affect common carp to address a regional overpopulation problem with the invasive species is being debated, with detractors raising safety concerns for the global food supply.
As reported in The Guardian, "Scientists in Britain have raised concerns about Australia's $15m plan to release a herpes virus in the nation's largest river system to eradicate carp, saying it poses a serious risk to global food security, could cause "catastrophic ecosystem crashes" in Australia, and is unlikely to control carp numbers long term."
"In a letter published in the Nature Ecology and Evolution journal this week, University of East Anglia researchers Dr Jackie Lighten and Prof Cock van Oosterhout say the "irreversible high-risk proposal" could have "serious ecological, environmental, and economic ramifications."
The specific agent -- Koi Herpes Virus -- is considered a highly efficient killer of common carp, and since it's initial recorded outbreak in Asia in the 1990's, has caused millions of dollars worth of losses to aqua culture and fishing industry. Carp are an important commercial food source in Asia and other middle income countries, helping to provide protein for perhaps a billion people worldwide, and any agent that could affect the species could also potentially affect the global food supply with associated economic and political instabilities.
Lighten and van Oosterhout go on to say that laboratory tests "cannot rule out the possibility of cross-infection" and that the virus will have "an enormous evolutionary potential" once released in the wild, and could evolve to attack other species. Additionally, the loss of oxygenation from rotting carcasses and resulting eutrophic event could potentially affect other species in the immediate environment.
However, the situation in Australia appears to have gotten out of hand.
Carp were introduced there over a century ago and now comprise over 90% of the biomass in many waterways, with devastating effect on indigenous species.
The Guardian continues, "Latrobe University senior ecology lecturer Dr Susan Lawler, who is based on the Murray River, said Lighten and van Oosterhout "don't understand the Australian perspective".
"The reason they are terrified of it going wrong is because they don't understand how terrified we are that all the native fish in Australia are going to die off because of carp," Lawler said. "There's an ecological disaster going on right now. I am not worried about it because at the moment these fish are dying anyway."
Owing to the nature of aquatic environments, infectious agents and contaminants spread easily to potentially affect large numbers of individual organisms. Within fresh water systems, the natural geographic barriers created by basin drainages can both incubate and isolate pathogens, allowing for evolution of agents that organisms in isolated ecologies have no natural defenses for. A case in point would be the outbreak of Whirling Disease in Colorado twenty years ago, where a myxosporean parasite endemic to European Brown trout was introduced to a hatchery population of Rainbow trout near Ft. Collins that were then released into state waters. The event resulted in the loss of almost 90% of Rainbows for several years regionally until minority populations developed resistance and repopulated.
Introduction of invasive species worldwide can carry unexpected outcomes that biologists are now only beginning to understand with more historical perspective. Globally restricted resources paired with a changing environment may make caution the order of the day while trying to make sense of a best way forward.