"Our study goes beyond just presenting barrier options by putting numbers to how effective various barriers will be, including hydrologic separation and the currently operating electric barrier system." Marion Wittmann, the paper's lead author and University of Notre Dame scientist, said.
The Notre Dame study used expert elicitation, a process of formalizing and quantifying experts' judgments to estimate Asian carp barrier effectiveness. Federal agencies such as the US EPA, NASA, US Army Corps of Engineers and the US Department of Transportation have successfully used similar expert elicitation in support of risk analysis and decision-making on issues ranging from food safety to radio-active waste management.
Experts estimated that hydrologic separation could prevent 95 to 100 per cent of Asian carp from entering the Great Lakes and an electric barrier could prevent between 85 and 95 per cent of introductions. Experts were much less confident about using sounds, bubbles or strobe lights to deter the invasive fish and indicated that the failure rate could be between 80 to 100 per cent for these methods, when used one at a time. However, using a combination of sounds, bubbles and strobe lights could prevent 75 to 95 per cent of Asian carp from entering Lake Michigan.
The study uses a method of expert elicitation designed by co-author Roger Cooke, senior fellow with Resources for the Future. Cooke's "Classical Method" weighs the opinion of each expert based on his or her knowledge and ability to judge relevant uncertainties.
"Our goal was to quantify uncertainty, not to remove it from the decision process," Cooke said.
On January 6 the US Army Corps of Engineers (Corps) submitted to Congress the Great Lakes and Mississippi River Interbasin Study (GLMRIS) Report which outlined eight possible scenarios for preventing Asian carp passage through the CAWS. The report provided no comparative evaluation of the options, but did indicate that developing infrastructure to keep Asian carp out of the Great Lakes could take decades and cost $15 billion or more.
"Protecting the Great Lakes from invasive species eventually comes down to understanding how effective a management strategy may be, how much it will cost and what the benefits of those options are," David Lodge, director of the University of Notre Dame's Environmental Change Initiative and co-author, said.
"Here we have estimated the efficiencies of various barriers without having to wait for more barrier testing and while the fish are swimming closer to the Great Lakes."
Environmental concerns are that if the Asian carp establish themselves in the Great Lakes, they will consume food sources of other fish, decimating local species.
"An important finding of this study is that knowledgeable experts identified clear differences in the likely effectiveness of some Asian carp prevention technologies as opposed to others," John Rothlisberger, co-author on the paper and aquatic ecologist with the USDA Forest Service, noted.
"Physical separation stands out from the rest as having the least associated uncertainty and the highest probability of preventing the introduction of Asian carp into Lake Michigan."