Posts Tagged 'Range'

Shell Shocked – – Florida’s Response to the Invasion of Exotic Apple Snails

As the renowned ecologist E. O. Wilson put it, “Florida rivals Hawaii in the magnitude of the threat from exotic species and for the same reasons: geographic insularity, widespread habitat disturbance, and bombardment from all sides by nonnative plants and animals.” Florida is the national gateway for foreign plants and animals for the ornamental plant, pet, and aquarium industries. In the face of this onslaught, Florida’s natural areas are losing their identity and function. I spent 35 years in DEP’s exemplary Bureau of Invasive Plants fighting over 1000 foreign plants established in Florida, now constituting 27% of our flora. My focus was on protecting the native aquatic plant communities that are so crucial to Florida’s lakes and wetlands.

As I was about to retire, the Island Apple Snail (Pomacea insularum) began to spread rapidly in Florida, efficiently devouring the very aquatic habitats I dedicated my career to protect. Consequently, I started this website to sound the alarm about exotic apple snails and assist resource managers fighting these invasive and destructive animals. Fortunately, there are many state and federal biologists who share my concern about exotic apple snails. The State of Mississippi has prohibited all members of Family Ampullariidae, calling them “destructive plant-eating apple snails.” Texas, Hawaii, California and Louisiana have identified them as agricultural pests that can negatively impact rice, taro and the production of other aquatic plants. At this time, Alabama is committed to prevent the range expansion of Pomacea insularum (see “Alabama Fights to Protect the Mobile-Tensaw River Delta). In Georgia, the Island Apple Snail has been given its highest priority for time and funding expended on control. What about Florida?

There are five stages of the response to the invasion of an exotic organism: 1. DENIAL – – “We know X is here, but it’s not a serious problem, so we don’t need to worry about it. Perhaps it won’t make it. Besides we have to deal with W, which is of more immediate concern.”2. ALARM – – “Oh, my gosh! Species X is multiplying fast and taking over the community. We must stop it.” 3. BARGAINING – – “Let’s put together rapid response teams. Perhaps, we can limit its expansion to a few areas and keep it out of critical habitat. We’ll have to divert some resources from dealing with species W, but if we have the opportunity to get on top of this we should.” 4. DEPRESSION: “We simply don’t have the resources to deal with X. Why didn’t somebody do something when it was manageable? We need better laws to keep these things out in the first place, but the commercial interests are just too strong.” 5. ACCEPTANCE: “I can’t worry about X right now, I just have discovered Y and we must deal with it now while we can!”

In September of 2005, the official position of the Florida Fish & Wildlife Conservation Commission (FWC) was: “Channeled Apple Snails [meaning P. insularum and canaliculata at that time because of taxonomic confusion] are non-indigenous to Florida and have been present in the state for over 20 years. They are a potential threat to our aquatic ecosystems, although no serious impacts have yet to be documented. Their greatest impact appears to be how they interact and possibly disrupt populations of native Florida Apple Snails, and FWC will be conducting research in this area” (see DENIAL Stage above). Subsequently, annual surveys conducted by FWC biologists of Florida’s 460 public water bodies noted a dramatic increase in the range of exotic apple snails. In 2006, four water bodies (4779 acres) were infested. In 2009, exotic apple snails were found in 75 water bodies comprising over 750,000 acres (60% of Florida’s freshwater areas). FWC will continue to take no action to prevent the spread of P. insularum “since it is widespread beyond reasonable control, and because the preliminary indications are that its impacts will be less than originally anticipated and, in some circumstances, there are beneficial effects” (see ACCEPTANCE stage above). For P. insularum, it was a very short hop from denial to acceptance.

Regarding the smaller, more isolated population of the Channeled Apple Snail (P. canaliculata) southeast of Jacksonville, it was a different story. FWC worked diligently toward eradication. Since May of 2008, the only known site of P. canaliculata, a 4-acre retention pond, has received constant attention. A crew of 5 or 6 people initially handpicked thousands of snails, then snails and eggs were collected there on a weekly basis. Recently, divers could find no snails. It is too early to be certain, but eradication may have actually been achieved . . . at least at that site. Other sites of P. canaliculata are rumored to exist in Duval County.

While FWC’s comparative lack of response to P. insularum might make sense given that it is so wide spread, the lack of concern regarding its ultimate environmental impact does not. There is simply too much taxonomic confusion to be sanguine: “Pomacea insularum and P. canaliculata pose the greatest threat to agriculture native aquatic wetland ecosystems in the U.S. [of all the apple snails]. The potential of P. canaliculata has been clearly demonstrated in Southeast Asia where its introduction . . . into Thailand resulted in dramatic changes in biodiversity and ecosystem functioning and by its devastating effects on agriculture. Some of the . . . impacts associated with P. canaliculata are almost certainly attributable to P. insularum. This species is also widespread in the region but has not been explicitly acknowledged as a serious pest because of confusion in the identification of these two species, with most of the literature referring to P. canaliculata. Pomacea insularum may therefore be likely to have a significant impact on aquatic ecosystems and pose a threat to crops in the southeastern U. S.” (Rawlings, T. A. et al., 2007).

Amazingly, it is still legal to buy, sell, and possess exotic apple snails in Florida, although last winter FWC politely asked Florida aquaculturists to stop selling P. insularum and P. canaliculata. “We work with DACS’s Division of Aquaculture to persuade culturists to stick to [selling only] the Spiketop Apple Snail (P. bridgesii), the only non-native apple snail that USDA will allow for interstate transport and one that has been in Florida for a while without apparent impacts” (Jenny Tinnell, FWC). Why allow the sale of P. canaliculata in Florida, after a heroic effort to eradicate them?

I know that some of you might be scratching your heads at this point. However, consider the plight of FWC’s Exotic Species Coordination Section with only 8 employees and an annual budget of less than $500,000. It has its hands full in this nation’s primary gateway for exotic animals dealing with Burmese Pythons, Nile Monitors, Green Iguanas, Vervet Monkeys, and 500 or so other exotic fish and wildlife species that have made their way to Florida. Against that line-up, exotic apple snails might seem rather mundane! Also keep in mind that the aquarium and pet industries are powerful economic and political interests in Florida who have successfully demanded minimal regulation. In response, “FWC has chosen to encourage responsible pet ownership rather than adopt a prohibitionist approach, which we believe would be ineffective [given] the substantial level of pet ownership [in Florida]and the industry that services this demand” (Scott Hardin, Section Leader).

Because P. insularum is clearly well-established in Florida, I hope FWC is correct in its assumption that these snails are innocuous, or even beneficial, to the aquatic environment. However, I seriously doubt it having personally witnessed P. insularum stripping the vegetation from Lake Munson, plus nearly doing so at Wellman Pond in spite of arduous snail control efforts. I admit to being very alarmed (see ALARM stage above). The next natural area that is in jeopardy near Tallahassee, in my opinion, is beautiful Lake Jackson, officially designated an Outstanding Florida Water and one of only four freshwater Aquatic Preserves in the the entire state. I wonder how this lake’s incredible, aquatic plant diversity will fare versus the on-going explosion of exotic snails. Maybe, if the Island Apple Snail strips Lake Jackson, FWC will finally take notice and put both the Island and Channeled Apple Snails on its list of “Conditional nonnative species,” those considered to be dangerous to the ecology and/or the health and welfare of the people of Florida. Until then, FWC appears “shell shocked” in the face of the rapid range expansion of exotic apple snails in Florida’s lakes, rivers and wetlands. Posted by Jess Van Dyke

For more information on FWC’s Exotic Species Coordination Section, contact:

Scott Hardin, Section Leader

850-410-0656 ext. 17257

FWC’s Non-Native Species:

Update: On July 1, 2012, Scott Hardin, former Leader of the Exotic Species Coordination Section for the Florida Fish and Wildlife Conservation Commission, joined the Pet Industry Joint Advisory Council, a group that lobbies for the interests of the pet industry in Washington, D.C.


Heading North . . .


. . . all the way to the “Red Zone” (7B, USDA Plant Hardiness Map)?

As the great philosopher and baseball “Hall-of-Famer,” Yogi Berra put it, “Making predictions is very difficult, especially about the future.” That is particularly true regarding the ultimate distribution of an invasive, exotic species. For instance, who would have predicted what would happen when three, small bundles aquatic plants from the Indian Subcontinent were placed into a canal near the Tampa airport around 1960? Unfortunately, those bundles contained one of the world’s worst weeds, Hydrilla verticillata. By the early 1970’s, hydrilla was established in almost all major water bodies in the state. At that time, the prevailing wisdom at Florida’s Bureau of Invasive Plants was that hydrilla might expand elsewhere in the Southern Coastal Plain, but none of us predicted that it would eventually reach Washington State and Maine. Certainly, the winter temperatures would stop this tropical plant, we all agreed. Hydrilla didn’t read the memo!

Now, in spite of Yogi’s admonition, scientists are trying to predict the ultimate range of the invasive, exotic apple snails (Pomacea canaliculata and P. insularum) in the Continental U.S. In the abstract of her exhaustive PhD dissertation on Pomacea insularum, Veena Ramakrishnan states that “the [laboratory] research results indicated that the main factor likely to limit the . . . distribution of P. insularum in North America was temperature, based on its incipient tolerated temperature range of 15.2°-36.6°C. Its 15°C lower lethal limit will restrict its distribution to southern and western coastal regions and Florida in the United States” (see Recent Publications, May, 2007)

The distribution predicted by Ramakrishnan would encompass the southern regions of Texas, Alabama, South Carolina, New Mexico and the southern and middle Pacific coastal regions and Sacramento Valley of California. “Particularly at risk to invasion by P. insularum is the state of Florida.” Her predicted range, though impressive, may be optimistically small. Further digging into the dissertation reveals that it took almost 27 straight days of exposure to 15oC to kill 99% of Pomacea insularum. Half of the snails survived for 5 days at 2oC. What will happen in the real world, where the snails aestivate in the bottom sediments during the winter? Worse yet, Pomacea canaliculata appears to more cold tolerant than P. insularum. Mochida (1991) reported that P. canaliculata can survive freezing for 15-20 days.

In its native Argentina, we know that “the southernmost record for [Pomacea] is Paso de las Piedras Reservoir (38o24’S), south of the Buenos Aires Province” (Martín et al., 2001). However, the local scientists have concluded that “hydrological discontinuity has been the barrier impeding the southward spread” into colder latitudes, not temperature (see Recent Publications for Martin & Francesco, 2006). In the Northern Hemisphere, the northernmost boundary of P. canaliculata is Kasumigaura Lake (36°06’N), Ibaraki Prefecture, Japan. In that area, “places of hibernation . . . were characterized by shallowness, high DO, and low pH, not by water temperature variations” (See Resent Publications for Ito, 2002).

In the U.S., an invasion of the exotic apple snails to Lat 36o would encompass most of North Carolina, Tennessee, and Arkansas, including most of that state’s vast rice producing areas. That may not be farfetched. The invasive snails have already been documented in Stoneville, N.C. (36o28’N). Will a broad range expansion to Lat 36o eventually happen? Who knows, but my guess is that that Pomacea insularum and P. canaliculata will ignore all of our speculative range maps and surprise us by heading north.   Posted by Jess Van Dyke 

2008: It was a very good year!

Live Island Apple Snails in the incurrent stream of Wellman Pond

live-snails-070830bYes, 2008 was a VERY good year . . . for exotic snails in Florida, that is. My former supervisor, Rob Kipker (FWCC), just emailed me fresh 2008 data on the presence of Island Apple Snail in the public waters of Florida. Each year, his team of top-notch, aquatic biologists inspects the Sunshine State’s 1.25 million acres of lakes and rivers with public boat ramps. Their primary mission is to survey aquatic plants, but for the past three years, Pomacea insularum has been on their list of species to mark “present” or “absent.” Rob wrote, “This is not a snail survey in the sense that we are documenting range, rather it is an indication of which of the 460 public waters in Florida currently have populations of the Island Apple Snail. Use at your own discretion.” O.K. and thanks, Rob!

The results of the 2008 survey reveal that 50 public waters (11%) are now are infested with the exotic Island Apple Snail. That’s bad enough, but the situation is worse when one takes into consideration the size of the affected waters. Some of Florida’s largest are on the list. The “800 lb. gorilla,” of course, is the Lake Okeechobee (448,000 ac), largest lake in the southern U.S., but Lakes Tsala Apopka (19,000 ac), Toho (31,500 ac), Kissimmee (35,000 ac), and the St. John’s River (96,000 ac) also have the exotic snails. Therefore, in terms of surface area, most of Florida’s public waters (55%) have populations of Pomacea insularum.

What about the future? There is every reason to believe that the Island Apple Snail will also have a very good 2009. There is a growing awareness that tropical cyclones play a major role in the dispersal of exotic species. The classic example occurred in 1992, when Hurricane Andrew destroyed much of the Miami Zoo, releasing parrots, baboons, orangutans, wallabies, capybaras, and more. One reptile dealer lost 10,000 geckoes, and a private research institution, 2000 monkeys. The hurricane facilitated a population explosion of large feral iguanas. South Florida will never be the same.

The dispersal of aquatic snails by tropical cyclones though more subtle is no less dramatic. In July 2000, exotic apple snails were discovered in the American Canal near Alvin, Texas (between Houston & Galveston). In June 2001, severe flooding from Tropical Storm Allison dispersed the snails throughout the entire region. In 2008, Cyclone Nargis hit Myanmar (formerly “Burma”) and spread the Golden Apple Snail (Pomacea canaliculata) into the vast rice production areas. “We have never seen so many. They have destroyed our fields,” said one rice farmer (see News Page).

In August of 2008, Tropical Storm Fay made a record four landfalls in Florida, zigzagging from land to water, and causing major, often record, flooding in 27 counties. Rainfall amounts included 27” in Melbourne, 23” at Cape Canaveral and 21” at Palm Shores. The St. Johns River overflowed in Jacksonville. Where I live east of Tallahassee, we received over 20” in a few hours. I’ve never seen flooding like that here. How can such a weather event not exacerbate the dispersal of the invasive apple snails in Florida? I have to believe that Pomacea insularum will put on quite a show in 2009. Happy New Year!! Posted by Jess Van Dyke

For more information on the survey, contact:

Invasive Plant Management Section (FWCC):


About Snail Busters

The Snail Busters Blog was created to facilitate communication between aquatic resource managers who are fighting the spread of invasive, South American apple snails, specifically Pomacea maculata (formerly P. insularum) and P. canaliculata, in the U.S.

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