Aquatic Invasive Species
Learn about the basic biology of the Amazonian apple snail (Pomacea maculate), how to identify it, how it was likely introduced, and the impacts of this aquatic nuisance. Also provided are instructions on what to do if this species is found.
Scientific Name: Pomacea maculata
Common Names: Amazonian apple snail, island apple snail
Native Region: South America
Date of U.S. Introduction: 1978
First Observed in Alabama: 2008
Known U.S. Range: Florida, Texas, Georgia, Mississippi, Louisiana, South Carolina, and Alabama
Presumed Means of Introduction: Aquarium trade
Recognized Impacts: Agricultural pest, especially in rice-growing areas; consumption of native wetland vegetation; potential human disease vector (nematodes and trematodes)
The Amazonian apple snail can grow quite large (up to 4 inches across) and has very round shells with 4 to 5 whorls. The shells are often yellow-brown, and the snail has an operculum, which it uses to seal up the shell opening. The Amazonian apple snail can be difficult to distinguish from the Florida apple snail, although this snail has rarely been found in Alabama. One of the most distinctive aspects of the Amazonian apple snail is the bright pink egg casings that they deposit near the waterline, usually in the springtime.
How Did They Get Here?
The Amazonian apple snail is one of several large apple snails that are popular with aquarists. Unfortunately, when the snails become too large, too abundant, or the aquarium owner no longer wishes to care for the aquarium, the snails, plants, and other animals in the aquarium are sometimes dumped in local waterways. This practice has led to the spread of several invasive, exotic species such as the aquarium plants hydrilla (Hydrilla verticillata) and Eurasian watermilfoil (Myriophyllum spicatum) that have cost many millions of dollars in control and management. The Amazonian apple snail was first found in Mobile County in 2008 and later at one site in Baldwin County. While it is not possible to know for certain, it is likely that the introduction of this invasive snail was from an aquarium source. Instead of using this method of disposal, aquarium owners should allow unwanted aquarium plants to dry thoroughly and then dispose of or compost them. Aquarium animals should never be released alive in Alabama’s waters, and it is illegal to intentionally stock or release aquatic organisms into the public waters of Alabama.
Why Are They a Problem?
Apple snails cause several problems. First, they can devastate rice crops, causing economic losses to farmers in neighboring states and reducing food supply in the southeastern United States. Second, they voraciously consume wetland plants. The damage the snails do by eating the plants can negatively affect all the important functions of our marshes and wetlands. Fish and wildlife (especially waterfowl) habitat can be severely damaged by these aggressive grazers, and they can directly compete with native wildlife for food and essential habitat. Damage to plants reduces the ability of marshes to absorb nutrients and stabilize sediments, leading to poor water quality in critical areas such as Mobile Bay and other coastal waters. A loss of these critical wetland plants can also reduce the ability of marshes to buffer the effects of large storms such as floods and hurricanes. Apple snails also serve as hosts of disease-causing trematodes and nematodes, including the rat ringworm (Angiostongylus cantonensis), intestinal fluke (Echinostoma ilocanum), and the human endoparasite rat lungworm (Eosinophilic meningoencephalitis).
Invasive apple snails mature quickly, reaching sexual maturity with 60 to 80 days. They can lay more than 2,000 eggs per mass and can lay new clutches of eggs nearly every 2 weeks. Eggs are laid on hard vertical surfaces near but above water surfaces and incubate for 1 to 2 weeks, at which point the newly hatched young snails fall into the water. In newly invaded regions, apple snails can spread by natural migration upstream and downstream, as well as through transport by people.
Apple snails can be extremely difficult to control and virtually impossible to eliminate once they have become established and are reproducing. Chemical control methods using copper-based compounds have been used to treat large areas. Unfortunately, the chemicals do not just kill the apple snails—copper can be toxic to algae, fish, and other snails and clams. Physical traps are often used to collect adult apple snails. These traps help monitor the snails to determine if they continue to spread. Removing or killing the eggs also reduces the reproduction of the snails. While the public can be vital in reporting the presence of this snail and not moving them to new areas, actual control is best done by trained professionals.
What to Do if You Find an Apple Snail or Egg Mass
Do not transport or move them. It is illegal to transport nuisance, invasive species in the state of Alabama.
Record the location and date you find the snail. Take a picture of the animal, and use a geo-tag if possible. Ideally, include something in the photograph for scale (a coin, for example).
Report the finding immediately to the Alabama Department of Conservation and Natural Resources, Division of Wildlife and Freshwater Fisheries. You can find your local fisheries biologist at http://www.outdooralabama.com/fishing/freshwater/staff/staff.pdf.
Note: If you are interested in doing more, state agencies periodically may have opportunities for volunteers to assist with control programs. Ask about these opportunities to learn more.
Any person, company, government agency, or other entity desiring to stock or release any fish, mussel, snail, crayfish, or their embryos into Alabama’s public freshwaters must obtain approval to do so by the Division of Wildlife and Freshwater Fisheries at 334-242-3471 or by email by contacting Nick Nichols, Fisheries Section, at firstname.lastname@example.org or by mail at the following address:
Alabama Wildlife and Freshwater Fisheries Division
64 North Union Street, Montgomery, AL 36104.