Wildlife experts are looking for evidence of carp DNA in the Mississippi River this week. While earlier tests turned up negative along the Mississippi, some are concerned that the invasive silver carp are on their way up the river.
Byron Karns, a biologist with the National Park Service, fishes along the river taking water samples that will be tested for silver carp DNA. The DNA is best found in fat cells that float above the water. Crews from the park service, the Department of Natural Resources and the U.S. Fish and Wildlife Service are joining in the effort.
"The DNA is typically contained in cells — obviously contained in cells of the animal — and cells are made up of a good amount of fats or lipids," Karns said. "They tend to float above the water, so it's important for us to grab surface samples for this testing."
The water samples are in half gallon jugs, taken out of the Mississippi below Lock and Dam No. 1. Crews in boats pack them in coolers, then take them to shore for processing and shipment to Indiana. There, technicians will look for the biological fingerprints of silver, black and bighead carp.
"This is such a new technology, there just isn't a lot folks out there that do this work," Karns said.
Similar testing found the telltale carp DNA in the St. Croix River in August, suggesting the silver carp have already made their way to Minnesota.
John Anfinson is with the National Park Service and helped organize a local task force to try and deal with the fish. He says their presence is all too apparent downriver. He saw for himself when the Army Corps of Engineers lowered a river pool near St. Louis.
"When the river dropped there in the backwaters, the beaches were lined with a 10-foot-wide window of dead Asian carp," Anfinson said.
Scientists think those fish may have made it as far as 50 miles up the St. Croix River. Tests from this same stretch of the Mississippi in June turned up negative. But river watchers want to check again.
"These carp prefer waters that aren't as clean. And you know the water clarity of the St. Croix is so much better than the Mississippi, that you'd think that they would have kept going up the Mississippi and not up the St. Croix. So it's puzzling," Anfinson said. "And the fact that the tests were negative here doesn't mean that the fish aren't here."
High water may have helped hide them over the summer. Floods in April and May and the river flow through the end of July were as much as three-times the seasonal average. This stretch of river may be the key to preventing the fish from moving further upstream.
Of more than two dozen dams built on the Mississippi, three are different. The dams at Keokuk, Iowa, in St. Paul and in downtown Minneapolis all have fixed spillways. Others have gates that lift to let the river through.
Fish can't get over the fixed spillway dams — except through the locks that let barge and boat traffic through.
So far, river traffic has kept locks open in Illinois, which some conservationists argue need to be closed to keep the fish out of the Great Lakes.
A draft action plan unveiled at a "Carp Summit" by Gov. Mark Dayton on Monday suggested a temporary move to close the lock, and dams here might be considered.
In the meantime, crews will continue taking water samples from the Minnesota River. Next week, they will head upstream from St. Anthony falls to Coon Rapids to collect more samples.
The DNA results are expected next month.