* Asian carp DNA found beyond barriers meant to block fish
* Great Lakes ecosystem at risk from invasive carp
* U.S. authorities weighing options, look for carp
By Andrew Stern
CHICAGO, Nov 20 There are signs Asian carp may have breached barriers designed to keep the prolific fish out of the Great Lakes, which could spell ecological disaster for the vital source of fresh water, authorities said on Friday.
Concentrations of DNA discovered by Notre Dame University researchers may indicate the presence of bighead and silver carp upstream from two electrical barriers designed to bottle up the invasive fish.
Environmentalists say that if the fish reach the Great Lakes, about 20 miles (32 km) from the barriers, they would quickly destroy the lakes' $4.5 billion fishery by consuming other fish and their food sources. Only Lake Superior among the five lakes may be too cold for the carp, which can reproduce rapidly and reach 100 pounds (45 kg).
The Great Lakes are the world's largest body of surface fresh water and are relied on by 30 million people in the United States and Canada for drinking water and recreation.
"This is devastating news," Andy Buchsbaum of the National Wildlife Federation said of the discovery of carp DNA in the Cal-Sag channel 8 miles (13 km) from Lake Michigan.
"We have to hope that there aren't enough population of fish to reproduce and create an epidemic of Asian carp in the lakes," he said.
The barriers are on the Chicago Sanitary Ship Canal, which is fed by several waterways that flow away from Lake Michigan. The canal is connected by various rivers to the Mississippi River.
Two electrical barriers constructed in recent years in the canal near Chicago were designed to shock the carp and keep them out of the lake.
The DNA could be from carp feces or eggs carried by ship and barge traffic, but it could indicate the carp have breached the barriers, Buchsbaum said.
Environmentalists called for the immediate closing of several locks separating the lakes from the inland waterways, and pressed for a permanent solution that would separate the Great Lakes from the Mississippi River watershed.
"Right now we have a last shot at keeping these carp out of Lake Michigan, and that's to close the locks," said Joel Brammeier of Alliance for the Great Lakes, an environmental group.
The U.S. Army Corps of Engineers said it and other agencies had met since Wednesday to consider the best course of action. Authorities will be sampling the channel to try to locate any loose carp.
"We're not discounting any options," which could include shutting the locks, a spokesman for the Corps of Engineers said.
The waterways are used by barges serving steel plants and other industry in the area. The lock separating the Chicago River from Lake Michigan would also be affected, although tour and pleasure boat traffic is down because of the season.
The invasive bighead and silver carp have come to dominate the Mississippi River watershed that is linked to Lake Michigan by a network of canals.
The carp were introduced into the Southern United States in the 1970s to help clean man-made fish farms. They escaped into the Mississippi River during flooding two decades later.
The omnivorous fish -- which are known to injure boaters because they often leap out of the water at the sound of a passing motor -- make up 95 percent of the biomass in sections of the Illinois River.
The Corps of Engineers said it would go ahead with planned maintenance on one of the two barriers beginning on Dec. 2. As part of the maintenance project, authorities will bar ship traffic and introduce a fish poison, rotenone, into several miles (km) of the Chicago Sanitary Ship Canal downstream from the barriers to kill all fish, including the carp. (Editing by Peter Cooney)