Study: Asian carp DNA may not signal live fish

— Live Asian carp don't necessarily have to be present for their DNA to turn up in the environment, according to a government study released Wednesday that could intensify the debate over how to prevent the aggressive, hungry invaders from reaching the Great Lakes and other vulnerable waters.



Scientists with the U.S. Army Corps of Engineers, the U.S. Fish and Wildlife Service and the U.S. Geological Survey are conducting a three-year study designed to answer questions raised by the repeated discovery of Asian carp DNA in rivers and canals in the Chicago area - including locations beyond an electric barrier intended to block the carp's northward march toward Lake Michigan. Their DNA also has been found in the Mississippi River beyond Minneapolis.

"The purpose ... is to improve the understanding and interpretation of Asian carp environmental DNA results, so we can refine and make this relatively young monitoring tool the most effective to detect live Asian carp presence," said Kelly Baerwaldt, an Army Corps fisheries biologist and Asian carp program manager. Additional reports are planned as the study continues.

Bighead and silver carp escaped into the Mississippi River from sewage treatment ponds and fish farms in the Deep South decades ago and have migrated northward, invading numerous tributary rivers. The filter feeders gobble massive volumes of plankton - microscopic plants and animals crucial to aquatic food webs.

Scientists say if allowed to infest the Great Lakes, the carp eventually could crowd out native species, endangering the region's $7 billion fishing industry. Silver carp, which spring from the water when startled and have collided jarringly with boaters, pose a threat to tourism.



Asian carp DNA discoveries also have ignited a debate over whether to close a Mississippi River shipping lock in Minnesota's Twin Cities area.


Without taking sides in the debate, the scientists found that fish-eating birds "have the capacity" to transmit carp DNA in their droppings, which could contaminate barges and other vessels. They found the telltale DNA in feces of birds that were fed Asian carp.

The study also found "considerable amounts" of DNA stuck to boat hulls, which can remain for days "and does not appear to be completely or quickly washed off of boats moving through the water."

Team members reported finding Asian carp DNA in Chicago's storm sewers. They said boats, nets and other gear used by commercial fishermen and natural resource agencies could spread the genetic markers.

Chris Jerde of the University of Notre Dame, who's among the scientists who have detected Asian carp DNA in recent years, said they never claimed that all the positive hits came from live fish. But alternatives suggested in the report don't explain the persistent DNA findings in the same general locations, he said.


"These patterns ... would seem to indicate that there's at least some live carp present in the system, although we don't know how many," Jerde said.

The Associated Press