The native Florida apple snail, Pomacea paludosa, a favorite food of the endangered snail kite and limpkin, now must compete for food and habitat with an apple snail from South America, the channeled apple snail (Pomacea canaliculata).The voracious channeled apple snail readily consumes almost any aquatic plant, and is particularly attracted to less coarse plants such as southern naiad (Najas guadalupensis), eelgrass (Vallisneria americana), and fanwort (Cabomba caroliniana). Their heavy feeding on aquatic plants could impact populations of invertebrates that are consumed by small fish, which are in turn eaten by larger fish like largemouth bass and crappie. Alligators, large turtles, and a few large birds may eat the channeled apple snails but probobly not enough to seriously impact the populations.

The channeled apple snail has been introduced into many areas around the world where it has become a serious agricultural pest (mainly of rice and taro). It threatens many natural lakes and wetlands due to habitat modification and competition with native species. Populations are established throughout Florida and breeding populations also exist in Texas, California and Hawaii. Individuals have been collected as far north as North Carolina and Ohio. Channeled apple snails frequently are marketed in the aquarium trade and may have been introduced by hobbyists, or possibly as eggs attached to aquatic plants planted in the lake, or as eggs attached to boat hulls. It is possible that populations will decline as the food supply is exhausted, which has occurred with other species of apple snails.

IDENTIFICATION
The shells of the channeled apple snails, Pomacea caniculata, vary from 1.5 - 2.3 inches (40 to 60 mm) wide and 1-3/4 - 3 inches (45 to 75 mm) high. The color in the wild is yellowish to brown with or without dark spiral bands. 5 to 6 whorls are separated by a deep, indented suture, hence the species name 'canaliculata' or 'channeled'. Reddish-pink eggs are loosely attached to each other with the mass being laid above the waterline on docks, seawalls, trees, and plant stems. An average clutch contains 200 to 600 eggs, with each egg measuring 2.20 to 3.5 mm (.86 to .138 inch) in diameter. Compared to the eggs of native apple snails, those of the channeled apple snail are smaller, pinker, and more numerous. Eggs hatch in one to two weeks, releasing hundreds of juveniles into the waterbody.

Comparison of Channeled Apple Snail & Florida Apple Snail

The shells of native apple snails, Pomacea paludosa, are 1.5 - 2 inches (40-55 mm) wide by 1-3/4 - 2.5 inches (45-65 mm) high, and are yellowish to greenish brown with red streaks and dark spiral bands. P. paludosa eggs are white to slightly pinkish and are laid on emergent stems of vegetation and trees. The clutches of 10 to 80 eggs are loosely packed together in a gelatinous mass. Compared with P. canaliculata, the eggs of Pomacea paludosa are relatively large, about 0.1" - 0.236" (3 to 6 mm) in diameter, but far fewer in number.

Florida LAKEWATCH volunteer Dave Scharr on Lake Wanautta earned kudos for his detective work four years ago when applesnails were devouring the eelgrass (Vallisneria americana) in his lake. Dave called the LAKEWATCH office with concerns about the voracious snails, triggering an investigation that eventually alerted the FWC and USGS biologists about the presence of the invasive species. Dave says he knew something was up when piles of dead eelgrass were washing up on his lake shoreline every morning. To solve the mystery, he installed a small wire enclosure around a patch of eelgrass to keep out turtles and/or grass carp - the initial suspects. The next morning, the grass was chewed off at the base and dozens of applesnails were found in the enclosure. At first, biologists were skeptical of his observations; according to them, the native applesnail is an algae grazer, not a grass grazer. However, after further study, it was determined that the ravenous snails were an exotic species. (i.e., the channeled applesnail) that closely resembles Florida's native applesnail. Fortunately, this story has a happy ending: the exotic snail population "crashed" soon after and the eelgrass has returned. - A. Richard, UF/CAIP