Creatures who use gills to breathe faced a new enemy when the Illinois Department of Natural Resources began dumping the odorless chemical rotenone into a 5-mile stretch of the Little Calumet River in an attempt to combat the growing threat of Asian carp in a five-mile stretch of the Little Calumet River. This is the second time rotenone has been deployed to kill the carp in the river in the past five months according to the U.S. Fish and Wildlife Service.

The decision to poison the river was made after Asian carp DNA was again found near the T.J. O’Brien Lock and Dam in Burnham, Ill. According to Chris McCloud, director of the Asian Carp Regional Coordinating Committee, more than 2,000 pounds of rotenone was introduced into the river on May 20. However, before the process began several prominent species of fish were removed from the river to preserve them by shocking them and relocating them.

After the initial dumping of rotenone, officials from the U.S. Fish and Wildlife Service and the Illinois Department of Natural Resources did not find any Asian carp corpses, which caused some doubt as to whether or not the carp are a direct threat to the Great Lakes at this point. However, more than 100,000 pounds of fish representing about 40 different other species of fish were found floating on the surface, said McCloud, who noted that the poison took 48 hours to dissipate in the water. The bodies of the fish were removed through the use of nets, said Ryan Aylesworth, a spokesperson for the U.S. Fish and Wildlife Service.

Aylesworth said the U.S. Fish and Wildlife Service and the Illinois Department of Natural Resources are currently reviewing the results of the Little Calumet River poisoning to determine if any Asian carp were missed and to plan the next step, although nothing is concrete at this time. Aylesworth said the agencies are keeping open the option of using rotenone again if more evidence of Asian carp is found in the area.

Current methods of DNA testing for Asian carp are under scrutiny by officials and shipping industries because the origin of the DNA is still not known. Yet McCloud said that because there are biotraces of the fish, there are most likely small communities of the invasive species in the river. According to federal officials, the DNA of the Asian carp could have been produced by the scales or waste products from the carp.

As previously reported by The Chronicle on Jan. 25, numerous water-shipping industries oppose closing the locks that act as gateways to Lake Michigan because such action has the potential to cause heavy damage these commercial interests. However, to complete the poisoning on May 20, the T.J. O’Brien Lock and Dam, which sits along one of the main shipping routes, was closed for several days.

“Rotenone is a very effective way to combat intrusive fish that don’t belong in the ecosystem,” said Ashley Spratt a representative of the U.S. Fish and Wildlife Service. “The poison isn’t threatening to humans or non-gilled animals when it is used properly.”

The Illinois Department of Natural Resources reported that the cost of the poisoning was close to $1.5 million, which according to Spratt, is nothing compared to the devastation the ecosystem could face if the Asian carp manage to get into Lake Michigan and the surrounding Great Lakes.

“These fish would consume all the food in the lake and basically starve the other species to death,” Spratt said. “The electric barriers already in place aren’t doing the job so we have to come up with new ways to prevent the carps spread.”

Currently, only two species of Asian carp have been identified; the silver cap and bighead, yet these two species can grow to more than 100 pounds. According to the Associated Press, the state of Michigan filed a lawsuit to close the Sanitary and Ship canal to prevent the carp’s entry into the Great Lakes. As of yet, the U.S. Supreme Court has not agreed to hear the case.