Opening spillways may move Asian carp

Randy LaBauve, Rutherford, Allen

News Release Distributed 06/07/11

Opening the Morganza and Bonnet Carre spillways to divert Mississippi River waters has caused concern that Asian carp could move from the Mississippi River into other Louisiana waters.

Although they may not cause additional problems in the Atchafalaya Basin, they could in Lake Pontchartrain and surrounding water bodies, according to LSU AgCenter experts.

Originally introduced into private U. S. ponds in the 1970s, Asian carp eventually escaped into the wild and rapidly multiplied. An invasive species, they began taking over water systems throughout the Mississippi and Missouri river basins by voraciously eating aquatic vegetation and robbing native fish of their food supply.

The fish were already well established in the Atchafalaya Basin before the spillway was opened, according to Allen Rutherford, director of the LSU AgCenter School of Renewable Resources and a fisheries expert

“I don’t think fishes passing through the Morganza Spillway are going to substantially increase numbers in the basin,” Rutherford said. “You’d have to increase the resources for that to happen.

“Temporarily they’ll be more widely distributed. But in the long term, as the basin river stages drop, it will not likely increase the abundance.”

Opening up the Bonnet Carre Spillway, however, may lead to increased abundance of Asian carp in Lake Pontchartrain and surrounding watersheds, he said.

Lake Pontchartrain has a mixture of different salinities. The southern part of the lake is typically more saline while the north shore has fresher water.

The Asian carp -- comprising both the “silver” and “bighead” species – is a freshwater fish and does not survive well in higher salinity waters.

Everything below the Rigolets Pass is saltwater, and that restricts Asian carp from spreading into more saline water south of that point, Rutherford said.

The north shore of the lake has more freshwater because Lake Maurepas and the Tangipahoa and Tchefuncte rivers flow into it. For that reason, higher numbers of Asian carp could invade the north shore portion of Lake Pontchartrain and freshwater rivers and lakes feeding into it.

In the past fish kills have occurred in Lake Pontchartrain after opening the Bonnet Carre Spillway, Rutherford said. “That’s because increased amounts of incoming nutrients create algal blooms that rob oxygen from the water. So that likely will kill Asian carp as well.

“But Asian carp are filter feeders that feed on algae and aquatic invertebrates. So some of them, in the intermediate term, may do ok. Whether they’re going to be a problem in Lake Pontchartrain, long term, is still up in the air,” he added.

Asian carp often jump into boats, causing injury to people and damage to property. Hence, they have been nicknamed “flying fish.”

The only known way to modestly curtail Asian carp populations is to harvest them.

Often confused with common carp, which has a reputation as a trash fish, Asian carp are a completely different species of fish.

They taste excellent and can be successfully cooked numerous ways. They’re also nutritious, low in fat and a good source of omega-3 fatty acids.

In many states, there’s no catch limit on Asian carp, but the “flying fish” are herbivores, so they can’t be caught with traditional bait. They can be caught by bow fishing, using hoop nets, or just waiting for them to jump into the boat.

“What we really need to do is eat more of them by establishing markets that can use these fishes,” Rutherford said.

The LSU AgCenter produced a video “Flying Fish, Great Dish!” demonstrating how to properly clean and prepare Asian carp. The program was made to encourage more consumption of the invasive fish.

DVDs are available free-of-charge from the Louisiana Sea Grant Communications Office in the Sea Grant Building on the LSU campus. They also can be ordered by contacting Jessica Schexnayder at at a cost of $6 to cover postage and handling.

Segments of the video program can be found on You Tube by putting “LSU AgCenter Asian Carp” in the search box.

Randy LaBauve

6/8/2011 12:13:43 AM
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