Two species of invasive Asian carp may be able to spawn in more Great Lakes tributaries than previously thought, according to a U.S. Geological Survey report released last week.
Researchers said they hope the new data will help predict where the fish could spawn if they make it from Chicago-area waterways into the Great Lakes, giving authorities a leg up in their fight to combat the hungry fish.
"If Asian carp spread into the Great Lakes, knowing where to expect them to spawn is a critical step in controlling these invasive species," scientist Elizabeth Murphy said in a statement.
The voracious eaters can reach 100 pounds, and experts worry they'd be able to out-compete native fish for food, threatening the lakes' $7 billion fishing industry.
Tuesday's report shows that fertilized Asian carp eggs can incubate in waterways that are only 26 km (16 miles) long. That's far shorter than the 100 km (62 miles) of undammed water that researchers previously thought the drifting eggs needed before they could hatch.
The USGS says the floating eggs are slightly heavier than water, which means they will sink — and, generally, die — if they get trapped in a slow-moving river, lake or stream. But the stretches of uninterrupted, moving water give the eggs a better chance of survival.
Several varieties of carp imported from Asia have migrated steadily northward in the Mississippi River and its tributaries since escaping from Southern fish farms and sewage treatment ponds in the 1970s.
The fish have since been spotted in more than two dozen states and have advanced to within 55 miles of Lake Michigan in the Illinois River, which connects with a shipping canal and other waters that reach Lake Michigan.
None of the carp are known to have reached the lakes, although their DNA has been found in Lake Erie. The Great Lakes region has been sharply divided over how to deal with the threat.