The current in the electric fish barriers near Chicago is being turned up in a stepped-up effort to keep invasive fish, including the dreaded Asian carp, from entering the Great Lakes, while studies continue to see if the barriers are effective or whether the fish may already be in Lake Michigan.

Studies in late July speculated that the invasive carp, which biologists fear could be devastating to the Great Lakes ecosystem, are within five miles of the Chicago Sanitary and Ship Canal, where the U. S. Army Corps of Engineers has set up the electric barriers. The barriers are designed to discourage the carp from swimming through the canal into Lake Michigan, but are still being tested for safety to boats and people.

The Corps announced it had set up a safety zone for the testing Friday, August 14.

Tests released July 31 indicated silver carp are 10 miles further into the system than anyone had thought. The new testing method samples water for traces of DNA left by the fish. Silver carp are one of three species of Asian carp that have entered the Mississippi River system. The other two are black and bighead carp.

The carp can reach up to 100 pounds and leap into the air when startled. They have reportedly injured fishermen and jet boat operators.

In response to the findings, the Corps doubled the voltage at the barrier from one volt to two volts and is studying the impact of that on boats and people.

Scientists have no proof that the barriers will even work against the invaders.