These are invasive Asian carp, going ballistic above the Illinois River, near Havana, Illinois, on a recent hot summer day. Asian carp leap out of the water at the sound of outboard motors. Nobody knows exactly why.

The carp, which first escaped an aquaculture facility in Mississippi in 1972, when the Mississippi River flooded, have been working their way north. They have become a watery epidemic, reproducing at a rabbit-like pace that shocks most aquatic biologists.