Scientists watching spread of invasive marine life

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Published: November 29,2011

Tags: environment, invasive species, marine life

MISSISSIPPI GULF COAST — Three invasive aquatic species — the silver carp, Asian tiger shrimp and lionfish — have been closely watched this year as they were sighted across the northern Gulf of Mexico.

“Recently, we were worried about the Mississippi River flooding that would introduce freshwater species,” Mike Pursley, aquatic invasive species coordinator for the Mississippi Department of Marine Resource, told members of the state Commission on Marine Resources.

However, there’s no evidence the diversion of Mississippi River floodwaters into the Mississippi Sound introduced invasive species, he said.

“The fish we were worried about most was the silver carp,” he said. “They are from Asia and they are highly prolific.”

The carp grow to 60 pounds and are a threat to boaters because they leap out of the water and have injured people, he said.

They also pose a threat to the ecology because they tear up water bottoms while feeding.

“The sightings so far have been mainly through the Mississippi River Valley, but with the flooding that we’ve seen recently they have been as far south as Lake Pontchartrain,” Pursley said. “The fear was they would come around the freshwater bridge that was created and get up into the Pearl, Wolf or even the Back Bay.”

Another fish sharing the trait of having a voracious appetite and spreading toward Mississippi waters is the lionfish, he said.

Lionfish are in Mobile Bay, 40 miles south of Dauphin Island, off the coast of Louisiana and up the East Coast, he said.

The lionfish live on reefs, reproduce rapidly and have no natural predators, Pursley said.

“Probably the most interesting thing we’ve got going on right now are the Asian tiger shrimp,” he said.

“They are the world’s most aqua-cultured shrimp because of their large size and very fast growth rate,” he said.

Their release into the wild is traced to an aquaculture operation in South Carolina in 1988 and recently it is believed they may be coming from aquaculture operations in the Caribbean, he said.

“As recently as a couple of years ago, it was thought that they would not survive in the northern Gulf of Mexico because of their lack of cold tolerance,” he said.

Pursley said selective breeding may have helped the tiger shrimp survive in colder waters.

“The worry is they would compete with our native shrimp for habitat and food and they could possibly bring disease,” Pusley said.

The shrimp have been sighted off Bellefontaine Point, Biloxi Channel, Round Island and Horn Island, he said.

The number of tiger shrimp reports “exploded” in 2011, he said.

The Asian tiger shrimp are more tolerant of freshwater, but it is not known if the influx of Mississippi River floodwater into the Mississippi Sound increased the sightings, he said.

There have been no reports of juvenile or any Asian tiger shrimp smaller than six inches, Pursley said. And, there is no indications they breed with native shrimp, he said.

Giant salvinia also has been troublesome, but it has been limited to one spot on the Pascagoula River, he said. The aquatic plant can choke out other vegetation.

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