Despite millions of dollars and thousands of hours spent researching the "cryptic" Asian carp as it has moved toward Chicago's waterways, scientists admit some of the most important aspects of the fish's life remain a mystery.
There is considerable debate in the scientific community about precisely where they are in the waterway system, what conditions are best for spawning, what triggered the fish's population explosion in the Mississippi and Illinois rivers, and, most importantly, whether Asian carp have the capability to destroy commercial and recreational fishing on the Great Lakes.
Testimony from noted fish biologists at the three-day hearing in federal court in Chicago that wrapped up Friday, as well as recent studies from researchers at the University of Illinois and Ohio State University, cast doubts on the Asian carp's ability to sustain a thriving population in the Great Lakes as so many have feared.
"I do believe individual (fish) will survive, but a large population? It's hard to say," testified U.S. Geological Survey biologist Duane Chapman, who has studied Asian carp in the U.S. and abroad for a decade. "We don't know what will happen, but we can make some guesses."
Calling the Asian carp's habits "cryptic," Chapman told Judge Robert M. Dow that even if Asian carp enter Lake Michigan in large numbers, it could take decades before scientists know whether the Great Lakes are suitable habitat for the carp's long-term survival.
It's an assessment supported by a study published this year in the science journal Freshwater Biology 2010. Researchers at the University of Illinois' Natural History Survey concluded that scarce supplies of plankton in the Great Lakes would make it unlikely that bighead and silver carp — the most common types of Asian carp in Illinois — could flourish there.
Independently, Konrad Dabrowski, a professor of aquatic sciences at Ohio State University, recently released a report based on his 15 years of study of Asian carp. Dabrowski maintains that water temperature, depth, the speed of currents and food shortages will be the Great Lakes' best defense against Asian carp — the ecosystem is vastly different than the one Asian carp have encountered on their long swim up the Mississippi and Illinois rivers.
"Based on the biological information available for … the Great Lakes and their tributaries, it is highly improbable that spawning of Asian carps may occur," Dabrowski said in an e-mail.
These studies refute, or at least contradict, testimony given to Congress this year and some of the commonly held beliefs about the threat Asian carp pose to the Great Lakes' precious $7 billion-a-year fishery.
"Once an invasive species gets established in the lakes, you cannot eradicate it," Rebecca Humphries, director of Michigan's Department of Natural Resources, told a U.S. House subcommittee in February. "The threat of Asian carp needs to be treated as a crisis."
A native of China with no known predators in the U.S., Asian carp have overwhelmed walleye, bass and other game fish by out-competing them for plankton.
The federal government has allocated nearly $80 million to help Illinois control the Asian carp's move toward Lake Michigan and reduce the impact on hard-hit fisheries Downstate. Illinois' handling of the carp crisis has led to a series of lawsuits, meetings in Congress and at the White House, and prompted the involvement of the U.S. Supreme Court.
In court last week, attorneys general from five Great Lakes states — Michigan, Ohio, Minnesota, Wisconsin and Pennsylvania — asked Judge Dow to grant an emergency injunction to force closure of locks at the mouth of the Chicago River and Calumet Sag-Channel, a move that could seal off Lake Michigan from the advancing carp but also sever a vital shipping corridor linking the Great Lakes with the Mississippi River. A verdict is expected this fall.
Whether this uncertainty among scientists changes the public debate about Asian carp remains to be seen, experts said.
Like Chapman, the university studies urge the government and wildlife officials to take whatever steps they can to prevent Asian carp from entering the Great Lakes. But, they say, the feared Asian carp invasion so many have forecast may not be realistic.
"Even if we put unlimited numbers of Asian carp (in the Great Lakes) they may not survive," Chapman said in court. "We simply don't know."