Report: DNA method helpful in seeking Asian carp
TRAVERSE CITY, Mich. (AP) – Federal officials
promised Friday to improve two crucial weapons in the fight to
prevent Asian carp from invading the Great Lakes: an electric fish
barrier near Chicago and an early-warning system that detects carp
DNA in waterways.
The U.S. Army Corps of Engineers released a report by four
independent scientists who analyzed the “environmental DNA”
process that government and university scientists have used the
past two years to search for the carp on both sides of the
The study concluded the means of detecting the carps’ genetic
material in water samples is fundamentally sound but should be
refined to answer questions such as whether the DNA came from live
carp and, if so, how many. Research to improve the system is under
way, Army Corps officials said.
The Corps also announced it was turning up the juice on the
barrier network in the Chicago Sanitary and Ship Canal, a man-made
link between Lake Michigan and the Mississippi River system. The
barrier is designed to prevent Asian carp and other fish from
migrating between watersheds and competing with native species for
food and living space.
The Obama administration has pledged more than $125 million to
protect the Great Lakes from bighead and silver carp, Asian
varieties that escaped from Southern fish farms and sewage lagoons
in the early 1970s and have migrated north in the Mississippi and
tributary rivers. Scientists say if the aggressive carp become
established in the Great Lakes, they might starve out other fish by
gobbling tiny fish and plants at the base of the food chain.
Five states _ Michigan, Ohio, Wisconsin, Minnesota and
Pennsylvania _ have filed a federal lawsuit calling for
re-engineering the Chicago canal to sever ties between the
Mississippi and Great Lakes drainage basins. The Army Corps plans
to release a report on that and other possible long-range solutions
to species migration in 2015. Chicago business interests say
cutting the link between the watersheds would devastate shipping
companies that use the canal.
A key issue in the debate is how well the electric barrier 37
miles south of Chicago is performing.
The Army Corps says there’s no evidence that any carp have
gotten through. The five states and environmentalists contend it’s
not foolproof, pointing to the discovery of Asian carp DNA, also
known as “eDNA,” in dozens of water samples taken from beyond the
barrier since fall of 2009. Business groups have questioned the
reliability of the DNA findings.
In the report released Friday, the independent scientists said
the methodology used to detect carp DNA in the water was solid. But
they called for improvements, saying it “does not unequivocally
indicate the physical presence of live bighead or silver
David Lodge, the University of Notre Dame biologist whose team
developed the DNA process, said he never claimed otherwise. The
advantage of DNA is that it’s easier to find than live fish, so it
provides an early indicator that carp might be present, he
“This should bring to a closure any questions about the
technical robustness or the usefulness of eDNA,” Lodge said.
“This also should make it possible to move quickly toward refining
the tool to provide more of the kinds of information that the
independent review team pointed out would be useful.”
While insisting the barrier is stopping fish migration, the
Corps said Friday that tests have shown the voltage could be
increased about 15 percent _ from 2 volts per inch to 2.3 volts per
inch _ without endangering people in passing vessels.
The adjustment will take place this fall and will make the
barrier even more effective, said Maj. Gen. John Peabody, commander
of the Great Lakes and Ohio River Division. Additionally, barrier’s
frequency will be doubled and its electric pulses will become more
“We think it’s prudent to take all precautionary steps possible
so long as we can do them safely,” Peabody said in a conference
call with reporters.
The Army Corps said its confidence in the barrier was based on
movements of 166 fish fitted with transmitter tags. Although
devices tracking the tags have recorded 1.9 million hits, none of
the fish have been spotted passing through the barrier, Peabody
said. One tag was found on the other side but it appears that fish
was snagged by an angler, said Kelly Baerwaldt, a Corps fishery
In June, the Corps released six fish – not Asian carps – just
above the barrier. Two passed through the force field but
apparently were immobilized, while two others entered the field and
apparently were killed. The final two swam upstream, Peabody
“We believe the barrier is effectively preventing the movement
of these tagged fish,” he said.
Thom Cmar, an attorney with the Natural Resources Defense
Council, said the barrier appears to be working most of the time
but is not foolproof.
“When you’ve got thousands of Asian carp teeming in the rivers
of Illinois and moving closer to the barriers all the time, there’s
every reason to believe some of them are testing the barriers
today,” Cmar said.