June 10, 2011
NEW ORLEANS — While scientists have been battling to keep a ravenous, invasive fish species out of the Great Lakes, some worry that spring floods along the Mississippi River may be spreading the Asian carp downstream.
Duane Chapman, a U.S. Geological Survey biologist and Asian carp expert, says the fish are likely to show up in places where Mississippi floodwaters intruded. They can weigh up to 100 pounds, grow 4 feet long and live for 25 years.
They could be crowding out food sources of native species for decades.
“I think there is a very serious issue here,” said Chapman. “We may now be finding them in lakes, ponds, bayous, anywhere the river water went. Those things will be full of carp now.”
Asian carp is a term applied to several related species of carp that were brought to the United States in the 1970s to control algae in catfish farms in the South. Floods washed them into the Mississippi River in the 1980s.
Since their escape into the wild, the carp have established themselves in the Mississippi and Missouri river basins. They endanger native fish by greedily eating aquatic vegetation and robbing local species of their food supply.
The battle to keep them out of the Great Lakes includes the use of underwater cameras and sonar to monitor the effectiveness of the Army Corps of Engineers’ electronic barriers.
The Mississippi’s spring floods inundated an estimated 6.5 million acres along a 1,000-mile stretch of winding river from Cape Girardeau, Mo., to the Mississippi’s mouth in Louisiana, said corps spokesman Bob Anderson.
In Missouri, the corps blew up a levee to send some of the river water into a floodway at Birds Point-New Madrid; it also opened the Morganza and Bonnet Carrie spillways in Louisiana.
“That entire area could see carp spreading to formerly virgin areas,” Chapman said.
In Mississippi, ponds holding farmed catfish have taken a heavy toll from backwater flooding. The industry says it may take a year to scrub out the ponds and remove much that was left behind, including Asian carp. They also will have to restock because their crop either swam away in the flood or died because of muck and foul water entering the ponds.
The carp thrive in fast-moving water, said Ruben Keller, a lecturer in environment studies at the University of Chicago who has worked extensively on Asian carp with the National Invasive Species Council.
“They spawn in high water events like the flood,” Keller said. “This will produce many more carp.”
Greg Lutz, professor of aquaculture at the Louisiana State University Agriculture Center, said that means big pressure on the food supply for fish. “There’s a rule of thumb for fish size and food consumption. You can say a 1-pound carp has eaten at least 10 pounds of plankton to get that size. So if you have hundreds of thousands of pounds of carp they are eating millions of pounds of plankton.”
The Yazoo River in Mississippi and the Atchafalaya River in Louisiana could be especially susceptible. Flooding has been extensive along the Yazoo as the Mississippi backed up into farmland and catfish farms.
Mike Kaller, an LSU biologist, said Asian carp have been found for several years in the southern end of the Atchafalaya basin, but not on its middle and northern segments.
But that may change now because the opening of the Morganza spillway west of Baton Rouge could bring fresh carp stocks into the wetlands that make up the northern part of the basin.
Mississippi water flowing through the Bonnet Carrie spillway near New Orleans is expect to spread the species into Lake Pontchartrain and Lake Maurepas and their tributaries.
The lakes are brackish — a mix of fresh and salt water.
Most freshwater species cannot survive in a salty environment. But the carp can.
“Asian carp unfortunately are the exception that can do fairly well in high-salinity water,” Chapman said.
How far the fish may spread because of the flood won’t be known for some time, he said.
“At this point we have to wait until after the flood dissipates before we can evaluate and see how bad it is.”