Scientists had some disappointing news this week for Illinois residents: Asian carp are still thriving in the Illinois River and are not dying from a virus.
There had been speculation a virus was responsible for a large fish kill near Peoria in late May, the Springfield (Ill.) State Journal Register reported Thursday. But microbiologists this week said tests indicate the fish died when they were stressed. That caused their immune systems to fail and they were then susceptible to bacteria.
"The densities (of Asian carp) are getting very high, and that can be a source of stress," Larry Willis, a microbiologist with the fish pathology lab at the Jake Wolf Fish Hatchery near Manito, Ill., told the newspaper.
The Asian carp were brought to the United States from China more than 10 years ago to help keep fish-rearing ponds clean, but subsequently escaped during flooding in the southern United States, the State Journal Register said.
Carp are filter feeders, consuming up to 40 percent of their body weight daily in plankton, microscopic plants and animals. Some scientists speculate increasing competition for food might be causing stress in the carp population.
Copyright 2006 by United Press International
Explore further: Diabetes drug found in freshwater is a potential cause of intersex fish