By JOHN FLESHER
AP Environmental Writer
TRAVERSE CITY, Mich. (AP) — Thousands of fish may die when poison is dumped into a canal near Lake Michigan, but it’s necessary to prevent an onslaught of Asian carp that could devastate the $7 billion Great Lakes sport fishery, officials said Monday.
Rotenone, a toxin derived from tropical plant roots, will be applied next month to a nearly 6-mile section of the Chicago Sanitary and Ship Canal when an electronic barrier is taken down for maintenance.
The substance poses no danger to humans, although the U.S. Environmental Protection Agency said people should not eat the fish it kills. Officials said they would use non-lethal electric shock to catch and move as many sport fish as possible before the rotenone is released.
The application “reflects a difficult, but critical team effort to protect the lakes against a destructive fish that could cause catastrophic damage to the Great Lakes ecosystem,” said Cameron Davis, a senior adviser to EPA chief Lisa Jackson.
The carp were imported for use at fish farms in the southern U.S. but escaped into the Mississippi River during floods in the 1990s and have migrated north since.
They can reach 4 feet long and more than 100 pounds. They gobble up to 20 percent of their weight daily in plankton, a crucial link in the Great Lakes food chain. With no natural predators, the carp could overrun native commercial and sport fish and soon become the dominant species, scientists say.
Scientists this year detected DNA of silver carp, an Asian species, within a mile of a barrier in the canal about 30 miles south of Lake Michigan.
The barrier gives fish an electric jolt designed to halt their advance and became fully operational in April. It is the more powerful of two that the U.S. Army Corps of Engineers has placed in the canal in Illinois. A third is scheduled to go online in fall 2010, said Col. Vincent Quarles, commander of the corps’ Chicago district.
The newer barrier must be deactivated for maintenance every four to six months. The canal will be treated with rotenone to deter Asian carp from slipping past when it is taken down for several days beginning Dec. 2.
Most of the fish killed will probably be non-sport varieties such as common carp, goldfish and gizzard shad, officials said. They will be retrieved and taken to a landfill.
An antidote will be applied following the treatment to neutralize the rotenone and limit its spread.
Great Lakes advocates reluctantly endorsed the action.
“Nobody wants to see a fish kill, but in this case, the agencies have no choice,” said Andy Buchsbaum, regional executive director for the National Wildlife Federation. “The stakes are so high because it only takes one Asian carp — even one Asian carp egg — to get a foothold in Lake Michigan and then it’s all over.”
But environmentalists described the electronic barriers and rotenone applications as stopgap measures.
“We’re buying an insurance policy that expires again in six months,” said Joel Brammeier, acting president of the Chicago-based Alliance for the Great Lakes.
The only long-term solution is to close or reroute the canal, an artificial link between the Great Lakes and Mississippi basins created by engineers more than a century ago, he said.
Physical barriers also are needed to prevent carp from swimming from the nearby Des Plaines River into the canal during flooding, Brammeier said.
The Army Corps is studying both possibilities, Quarles said. But he said the newer barrier’s design was tested in a lab before deployment and proved effective in repelling Asian carp.
“From what we know today, the barriers seem to be effective for what they were designed to do,” Quarles said. “We continue to learn and make them better.”