CHICAGO (CBS) — When engineers reversed the flow of the Chicago River more than 100 years ago, they connected the Mississippi River basin to Lake Michigan. Now, charter boat captains from around the Great Lakes have asked Congress to put up a permanent barrier to keep Asian carp out of the lakes.

Guy Lopez has seen Asian carp first-hand on the Illinois River, as they jumped out of the water.

“Water erupted like a volcano, almost. There were silver missiles flying everywhere,” he said. “They jumped in our boat and struck my partner.”

Lopez runs Wild Dog Tackle & Good Guyde Service, a charter fishing boat that operates on the Illinois River and Lake Michigan.

He and other charter captains want a permanent physical barrier built near the existing electric barrier in the Chicago Sanitary and Ship Canal to keep Asian carp from swimming into Lake Michigan.

“The electrical barrier is a stopgap measure. How effective it is is not clear. The only way to truly prevent these things from getting in the Great Lakes is to separate the two basins, as they were originally,” he said.

Doing so would have a major impact on shipping, but the captains argue the cost to the Great Lakes could be devastating if Asian carp end up there.

“You have a multi-billion dollar salmon fishery on Lake Michigan right now, and we continue to add new invasive species,” he said.

The U.S. Army Corps of Engineers has estimated physical separation of the two waterways could take 25 years and cost $15 billion to $18 billion. Much of that cost would be required to build new runoff tunnels to reduce the increased risks of flooding.