Apple snails continue invasion of Houma-Thibodaux

These are a few of the apple-snail shells that were found near the Chacahoula swamp in 2008.

Published: Sunday, August 21, 2011 at 6:01 a.m.
Last Modified: Sunday, August 21, 2011 at 10:46 a.m.

During warm months, their alien, bubblegum-pink eggs dot the waterline in Bayou Black, Chacahoula and now, Bayou Terrebonne. Invasive apple snails gained a foothold in Terrebonne Parish in 2008, and scientists say they're steadily spreading.

“There's really very little you can do but sit back and watch the invasion,” said Michael Massimi, invasive species director with the Barataria-Terrebonne National Estuary Program in Thibodaux.

Massimi said two cold winters in 2009 and 2010 helped to knock back the snails' population in Terrebonne.

But the warm, wet weather has brought them back, and they're spreading again.

Jade Leboeuf of Houma said he and others have spotted lots of the snails in Bayou Black near his house in Gibson.

The first sign that apple snails have established themselves in a waterway is their eggs, Massimi said. The snails crawl out of the water during warm months and lay bright pink eggs a few feet above the waterline.

The aquatic snails can lay between 200-600 tiny eggs in one bunch. They'll continue to lay eggs as long as the weather is warm and could be reproducing through fall. They do have some local predators, including raccoons, minks, otters, wading birds, turtles and alligators. When they're very small, even crawfish may eat them.

But they reproduce so rapidly that predators can't keep up, Massimi said. It would take another long, cold winter or a strong drought to battle back the snails.

Apple snails have been documented in Florida, Texas and California, but it's only recently that they've began popping up in Louisiana, much to the concern of scientists.

The snails were first sighted in the Donner and Chacahoula areas in 2008. A separate population was also found in Bayou Black. Apple snails have been sighted in other parts of Louisiana, including Gretna, Lafitte and in the Barataria Basin.

The snails are common in the pet trade, Massimi said, and that's likely how they reached Terrebonne, probably dumped into local waterways by a disenchanted aquarium owner.

With multiple, growing populations in Terrebonne, Massimi said he's worried the snails could spread even further hitching a ride on boats or carried by curious children.

They may also spread through Terrebonne's intricately connected system of drainage canals, he said.

In the lush swamps of south Louisiana, tropical invasive plants and animals can cause problems in the environment, thriving to the point where they outgrow native species.

Apple snails are new to the system, and scientists can only speculate on the impact they'll have. They've invaded environments in Florida and Texas and are also an invasive species to southeast Asia, where they've been a major source of rice-crop damage.

“It's a mixed bag,” Massimi said. “The impacts may not be that severe. They could have an impact on the submerged aquatic vegetation.”

If the snails decimate the underwater vegetation, the water can become muddy and filled with algae, ruining the habitat for the rest of the critters

The snails are extremely hard to get rid of once they do populate an area. There are some effective pesticides, but they also kill all other species in the process, Massimi said.

Enola Elliot, a Houma resident, said her sister spotted the eggs near her house in Schriever. When she called to report them, wildlife officials told her to knock the egg clusters into the water.

Massimi said that's the best thing you can do to combat the snails. You can also collect and kill the individual snails.

Staff Writer Nikki Buskey can be reached at 857-2205 or


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