Despite laboratory evidence earlier this year showing that the electrical barrier in the Chicago area has not been strong enough to repel young Asian carp, tagging similar fish species below the barrier and tracking them shows that they are not crossing the barrier, the Army Corps of Engineers said Friday.
No fish, large or small, tagged in testing this summer crossed it.
Still, the corps plans to increase the barrier voltage from 2 volts to 2.3 volts to be certain, said Maj. Gen. John Peabody, commander of the Great Lakes and Ohio region of the corps.
The corps also said an independent scientific review of DNA testing showed the methodology is sound, even though it does not show how many fish are in an area or how long they've been there. It also doesn't prove whether the fish are alive.
DNA testing in the past two years showed repeatedly that Asian carp are past the barrier in the Chicago Sanitary and Ship Canal, but electrofishing found only a single carp, in Lake Calumet, 6 miles from Lake Michigan. Some argue the DNA might have come from fish parts eaten by birds or from dead carp that landed on barge decks and were carried through the barrier and landed in the water beyond it.
But several science reviews have said the DNA testing is valid. Dr. David Lodge said Friday that it can detect the fish at much lower levels than electrofishing. Peabody said DNA testing is a valid tool to show where carp might be and where to focus efforts to keep them away, rather than to say definitively where they are. DNA testing in Minnesota's St. Croix River showed evidence of Asian carp this summer, but electrofishing failed to find any.