Archive Page 2

False Hope of the Boom-and-Bust Model

It has been a long time since my last post. The problem has not been “writer’s block” but the lack of an interesting topic. It has been very quiet in the southern U.S. regarding exotic Pomacea. Though the USFWS in Alabama continues to struggle against Pomacea insularum at two locations, officials in the rest of the South seem complacent regarding exotic Pomacea. In Florida, the official dogma is that “they tend to boom-and-bust without causing much harm. Besides, they have already spread everywhere.” I am less sanguine.

Regarding the boom-and-bust rationale for official inaction, Dr. Daniel Simberloff and Leah Gibbons (2004) said it best: “Substantial populations of invasive non-indigenous species occasionally collapse dramatically. Although disease is often invoked, the causes are rarely studied experimentally and/or quantitatively, and some collapses remain quite mysterious. Except for the few species in which spontaneous collapse has been repeatedly observed, the possibility of such an event is unwarranted as a potential rationale for a do-nothing approach to management.”

In an exhaustive study of the impact of alien species in the Mediterranean Sea, Dr. Charles Boudouresque et al. (2005) concluded, “The boom-and-bust model predicts the eventual decline of the invasive species and the recovery of the native ecosystem. In fact, species introductions are irreversible, even at a geological scale, and the natural decline of introduced species is quite uncommon. Data have been misinterpreted, leading to the generalization of the probably rare boom-and-bust model.” The graph below depicts the typical population volatility of an introduced species which is not to be confused with a permanent “bust.”

Often, the interaction between a species’ population size and its habitat is subtle. Populations fluctuate due to density-dependent factors, such as disease,
parasitism, predation, and competition, and due to density independent factors, like the weather. As I was driving my tractor through the smoky haze blanketing my farm while disking fire lanes, I pondered, “What is the primary factor causing the perceived bust in the exotic snail populations? What if it is not subtle in this case but so obvious that it is hidden in plain sight?” Then, it hit me – – the exceptional drought plaguing the Southern U.S. has temporarily stemmed the proliferation of exotic Pomacea and spawned official complacency. It makes sense because current “exceptional drought” map of the U.S. generously overlaps the range of P. insularum.

While flooding is documented to assist the range expansion of exotic Pomacea, if not the eggs, one can logically conclude that extreme drought should be detrimental. To test my hypothesis, I took a walk around Wellman Pond, the test site for our apple snail traps and my favorite place to observe Pomacea insularum. I had not visited the site for months, and while I expected some impact of the recent drought, I was amazed to see the lowest water level ever. As I walked on the dry lake bottom within the periphery of emersed vegetation, I saw numerous dead snails, stranded egg clusters, and an army of foraging fire ants (See “Rematch: Pomacea versus the Red Fire Ant”). Clearly, the exotic Pomacea have had a difficult spring season in 2011 at Wellman Pond . . . and likely elsewhere in the South.

The image above is typical of the entire shoreline of Wellman Pond. Fire Ants are devouring most of the snail eggs, while the adult snails have lost access to the refuge from predation and egg laying substrate provided by the emersed vegetation. These hard times for exotic apple snails will surely end on Wellman Pond and elsewhere in the southern United States. The current rainfall deficit will inevitably swing the other way. In some future wet period, the expansion of the exotic Pomacea will likely resume with a vengeance. The snails are more vulnerable to control efforts now than ever. This is no time for official complacency based on the false hope of the boom-and-bust model. Posted by Jess Van Dyke

Pomacea’s Incredible, Indigestible Eggs

I have often wondered why the eggs of Pomacea canaliculata and P. insularum are not quickly devoured by any number of predators. The pink clusters draped on emergent plant stems around lakes could not be more obvious. However, these numerous clumps of protein and carbohydrates go largely untouched aside from occasional attacks by red fire ants, Solenopsis invicta (see post entitled, “Rematch: Pomacea versus Red Fire Ant”). Finally, a fascinating answer to this mystery has been provided by the outstanding team of Professors Dreon, Ituarte, and Heras of the National University of La Plata in Argentina.

Throughout the natural world, undefended eggs provide easy, nutritious meals. It is common for half of them to be lost to predation. Most animals rely on either hiding their vulnerable ova, guarding them, or producing so many eggs that a future generation is assured. No doubt Pomacea are prodigious breeders, but they also employ “aposematism,” a common characteristic of dangerous prey. Using warning signals, such as color, sound, or odors, certain prey clearly advertize that it is unwise to attack them. Such warnings are beneficial to both predator and prey. Certainly, the blatant display of bright-pink eggs by exotic Pomacea is the form of aposematism, called “warning coloration,” but what could possibly be danger in eating them?

Endowing eggs with chemical defenses in not uncommon in invertebrates, and Dreon, Heras, et al., (2008) already established that Pomacea canaliculata eggs contained such a predator repellant. The authors found that a rare protein neurotoxin was produced by albumen secretory cells in developing Pomacea canaliculata eggs. Further, they demonstrated that injections of this neurotoxin, called Perivitellin-2 or PV2, had lethal effects on rodents (LD50, 96 h @ 2.3 mg/kg) primarily because of damage to their spinal cords. However, this neurotoxin was fragile (heat sensitive), however, and there was evidence of antibody response to sublethal doses. The presence of PV2 did not seem enough to dissuade almost all predators from consuming Pomacea eggs suggesting some complementary defensive mechanism.

The rest of the story is provided in a publication this month by the same team (see Dreon, Ituarte, and Heras (2010) in Recent Publications). It is hard to imagine eggs that are not highly nutritious, and developing apple snail ova are “filled with large amounts of polysaccharides and proteins,” as the authors put it. However, there is another surprise for predators in the perivitellin fluid that surrounds the fertilized Pomacea oocyte, besides PV2. The same brightly-colored, caratenoid  protein, called ovorubin, that warns away predators and blocks damaging solar radiation is also a proteinase inhibitor. Feeding trials revealed that rats fed ovorubin lost weight because it binds to trypsin, a common digestive enzyme that breaks down proteins.

In an elegant defense of her young, the female snail not only adds a neurotoxin to the perivitellin fluid, but for good measure, colors it bright-pink with a compound that impedes digestion of protein. “This [protease inhibitor] role has not been reported in the animal kingdom, but it is similar to plant defenses against herbivory,” state the authors. Only red fire ants are determined enough to ignore the apple snail’s clear warning. A common TV advertisement trumpets that chicken ova are “incredible, edible eggs.” Well, the apple snail’s brightly-colored advertisement to predators is: “These are my incredible, indigestible eggs!” Posted by Jess Van Dyke

[Note: I started this weblog two years ago. Subsequently, there have been 24,000 hits from all over the world. I am grateful to all my old and new friends. Thanks for your help and encouragement!]

Bioaccumulation of Cyanotoxins in Apple Snails

Snail Kite (Rostrhamus sociabilis) on Lake Catemaco, Mexico (http://dematac.org/quejas.html)

               Bioaccumulation is the sequence of processes in an ecosystem by which certain chemicals can accumulate in organisms up the food chain, generally through a series of prey-predator relationships. If the chemical is highly toxic, the results can be devastating in an aquatic ecosystem. Since 1999, 54 bald eagles (Haliaeetus leucocephalus) have died on Lake Thurmond (71,000 acres), the largest such mortality in U.S. history. Dr. Susan Wilde, an assistant professor at University of Georgia’s Warnell School of Forestry, is part of the team that believes they have solved this mystery. She and her associates have concluded that the cause is bioaccumulation of a new neurotoxin produced by a newly described cyanobacterial species in the order Stigonematales.

               Produced by filamentous blue-green algae (cyanobacteria) growing on submerged plants, especially hydrilla verticillata, this neurotoxin is bioaccumulated from the vegetarian American coots (Fulica americana) to their magnificent predators, bald eagles. Consumption of vegetation containing the neurotoxin by coots and the consumption of sickened coots by eagles resulted in the discovery of an emerging neurological disease, called Avian Vacuolar Myelinopathy (AVM). This often fatal disease results from lesions in the brain stem and spinal cord. Coots affected with AVM lose vision and muscle coordination, have difficulty flying and swimming, and become easy prey for the opportunistic bald eagles, who themsleves become victims. The disease agent, a neurotoxin produced by an epiphytic bluegreen alga in the order Stigonematales (Wilde et al., 2005), has recently been extracted from the plant samples from problem lakes (Wiley et al., 2009). Test animals exposed to this extract contracted AVM. The evidence seems clear.

               Unfortunately, this emerging neurotoxin is not the only cyanotoxin in aquatic ecosystems with the potential for bioaccumulation. Microcystin is one that affects the liver long term. Another is Cylindrospermopsin which is rapidly becoming is one of the most important toxins produced by freshwater blue-green algae. The rapid distribution of cyanotoxin producers into temperate zones has heightening concerns that these toxins will create serious environmental and human health risks on a global scale. Importantly, a recent study in Mexico documented the bioaccumulation of cyanotoxins by native apple snails. In eutrophic Lake Catemaco (18,000 acres), Cylindrospermopsin was biomagnified 157 times by endemic Tegogolo snails (Pomacea patula catemacensis) (Berry, J.P., and Owen Lind, 2010, in press). That is not comforting.

               These findings raise serious questions regarding an additional environmental impact of the range expansion of exotic apple snails. It appears that the key ingredients for bioaccumulation of cyanotoxins are nutrient-rich aquatic systems, especially reservoirs, with abundant submersed vegetation covered with filamentous, blue-green algae. Because of nutrient pollution and the introduction of exotic plants, such systems are all too common in the expanding range of Pomacea canaliculata and P. insularum in the United States. Will exotic apple snails play the same role as the American coot and lethally transfer cyanotoxins to their avian predators, such as the Limpkin (Aramus guarauna) and Snail Kites (Rostrhamus sociabilis)? I asked Dr. Wilde:

               “Hydrilla mats provide an enormous substrate for epiphytic cyanobacteria, and many of these species are capable of producing toxins. Because they are voracious consumers of hydrilla, the invasive apple snails may facilitate the transfer of those toxins through the food chain. We have ongoing research funded by the Florida Fish and Wildlife Conservation Commission to determine the levels of toxins in tissues of exotic apple snails and the potential of transferring of those toxins to birds of prey. Our initial feeding trials indicate that concern may be warranted, but it is too early to make any definitive conclusions.”  She will keep us posted on her new, excellent website (below). Thank you, Dr. Wilde! Posted by Jess Van Dyke

For more information on AVM contact:

 Dr. Susan B. Wilde

Warnell School of Forestry and Natural Resources,

University of Georgia

Athens, Georgia 30602

706-542-3346

swilde@warnell.uga.edu

Avian Vacuolar Myelinopathy (AVM) Website:

http://www.forestry.uga.edu/swilde/

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

scott.hardin@myfwc.com

FWC’s Non-Native Species:

http://myfwc.com/WILDLIFEHABITATS/Nonnative_index.htm

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.

http://reptilechannel.com/reptile-news/2012/06/28/scott-hardin-joins-pijac-staff-as-consultant.aspx

Trapping Tons of Exotic Snails from Wellman Pond

Newly Planted Wellman Pond (9/2007)

 Officially opened on June 1, 2009, Martha Wellman Park provides a lighted, paved loop around a beautiful pond and a perfect place for us to study the Island Apple Snail (Pomacea insularum). Aside from easy access, the gradual slope of the bathymetry, and relatively firm substrate, the burgeoning exotic snail population made this 15-acre (6.1 ha) pond ideal for our work. We also had a great incentive to learn how to control the exotic snails there. As part of the construction of this stormwater treatment pond, a large number of native, emergent plants were placed along the entire shoreline at a cost of $565,000 – – Soft-stem Rush (142,124), Duck Potato (51,227), Arrowhead (22,673) and Pickerelweed (27,468).  After one growing season, 75% of the emergent plants were gone, including all of the Arrowhead and Pickerelweed.

Dense population of Pomacea insularum (2007)

In the fall of 2007, we began hand-collecting snail eggs and adults in Wellman Pond to save the extensive littoral planting effort funded by the FWCC from the voracious Island Apple Snail. Manually controlling the snails and eggs helped, but clearly something more efficient was needed. In the spring of 2008, we began testing various baiting and trapping methods. We had observed that the exotic snails had excellent chemoreception and could be easily attracted to certain foods. We also noted their proclivity to hide in black plastic (HDPE) flower pots, especially under any broad lip. Finally, we could see that the snail’s mobility was impeded by thin, vertical planes not touching the bottom. Putting this all together, we devised a trapping system that is highly effective on exotic apple snails.

Apple Snail Trap in Wellman Pond 

With funding from Blueprint 2000 and Leon County, we deployed 30 Snail Busters’ Apple Snail Traps (patent pending) in Wellman Pond in 2008 and 2009. As we cleaned and baited the traps, we also collected any eggs and adults we observed.  By the end of 2008, we had removed 4.16 tons of snails and 2,135,200 individual eggs! In 2009, the numbers dropped to 0.89 tons of snails and 1,106,400 individual eggs, in response to a much smaller population. This snail control program has stabilized the aquatic plants and the remaining plants were saved. Since these efforts were instituted there has been no subsequent loss of plants in the pond. The surviving plants are growing and reproducing. We are seeing a lot of new growth in the pond for the first time in the past two years. This is the best barometer of success. Posted by Jess Van Dyke

Wellman Pond (9/2009)

The Pomacea Project – – A New Website on Florida Apple Snails

Pomacea paludosa laying eggs

Sometimes, it takes the population decline of a beautiful animal like the Snail Kite (Rostrhamus sociabilis) to draw attention to the importance of, as The Pomacea Project puts it, “less charismatic” species like the native Florida apple snail (Pomacea paludosa). Clearly, the fate of the endangered Snail Kite hinges on the density of its apple snail prey. Patty Valentine-Darby and her husband Dr. Phillip C. Darby, Associate Professor at University of West Florida, were early in understanding that the density of the native apple snail could be used to determine the health of Florida’s aquatic habitats, in general: “Given their relative immobility and sensitivity to changes in water level and plant community structure, apple snails are an excellent indicator of local habitat conditions.”  In the late 90’s, while Phil was conducting his PhD research on P. paludosa, Patty was publishing kite-related papers, such as “Seasonal Patterns of Habitat Use by Snail Kites in Florida.” Since then, Patty and Dr. Phil Darby have made quite a team when it comes to wetlands ecology, specifically concerning the role of the Florida apple snail as a proverbial canary in Florida’s wetland “coal mine.”  

In 2005, Patty and Phil conceived the idea of creating a website to support other biologists who share the view that Florida apple snails act “a barometer of Florida wetland ecosystem health.” Incorporated in 2008, the Pomacea Project gained its official not-for-profit status this year. Subsequently, The Pomacea Project received funding the National Park Service to “to summarize available information on apple snails, snail kites, and other snail predators, including management recommendations to improve habitat conditions for these species.” Though this document will not be completed until 2012, a website is now available “to provide conservation and management information pertinent to the immediate needs of natural resource managers and the general public.”     

The Pomacea Project website became available this week and already contains a wealth of information on native apple snails, including basic biology, sampling methods, and management issues. The impacts of dry downs, exotic snails, and predators are discussed. There is an online brochure cleverly entitled “The 60-Second Snail – – a primer on apple snails when you only have a minute.” To me, the page with the greatest potential is the “Status and Trends” page, where observations on apple snail densities from eight of the most important apple snail habitats are recorded and updated. They hope to expand this effort to many other wetlands and lakes in the future. All in all, Patty & Phil have done a great job on this new site. They currently do not have funding to support updating and expanding their website. Check it out and, if you can, help them out by making a tax-deductible donation! Posted by Jess Van Dyke  

The Pomacea Project:  

http://www.pomaceaproject.org

Alabama Fights to Protect the Mobile-Tensaw River Delta

Kill the SnailsI recently spoke with Ben Ricks, District Fisheries Biologist with the Alabama Department of Conservation and Natural Resources (ADCNR), Wildlife and Freshwater Fisheries Division (WFF) about the recent team effort to eradicate exotic apple snails (Pomacea insularum) in Langan Municipal Park Lake and Threemile Creek, Mobile, Alabama (see Recent News). Ben had a positive attitude, “Everything went as well as could be expected given the short period to prepare. We got rid of a bunch of snails!”

While Langan Lake and Threemile Creek are important aquatic assets for Mobile, the urgency of this battle comes from the fact that they are connected to a true ecological gem, the Mobile-Tensaw Delta. Within this National Natural Landmark, more than 300 square miles of marshes, swamps, and bottomlands are now in danger of invasion by the exotic apple snails. This summer, the exotic apple snails were sighted only one mile upstream from one of the most biologically diverse and second largest river deltas in the U.S.

WFF sought assistance and council from a number of experts, volunteer organizations, and public agencies: The City of Mobile, Alabama Department of Environmental Management, Alabama Department of Public Health, Alabama Marine Resources Division, U.S. Fish &Wildlife Service, Environmental Protection Agency, Mobile Baykeeper and the Mobile Bay National Estuary Program. Even Snail Busters contributed to the effort by providing thirty, deeply-discounted apple snail traps.

The control project had a three-pronged approach: trapping adults, scraping the eggs, and treating the adults with copper. Three days before the copper treatments, Snail Busters’ traps were used to assess the initial population. “The traps worked great,” Ben said. “They really did the job!” During the treatment, the minnow traps were used as “sentinel traps” to obtain an estimate of the efficacy of the copper treatment. “Sixty to seventy percent of the snails inside the traps were dead after treatment.”

Two tons of copper sulfate was applied to Langan Pond and Threemile Creek using a blower to achieve the target of 2 ppm copper sulfate (0.5 ppm elemental copper). “Four ppm killed them every time in the lab, but 2 ppm also worked well” Ben said. In deference to preventing non-target mortality, they used the lower concentration. “Not a single fish died,” Ben happily reported. “Some Asiatic Clams (Corbicula fluminea) were killed, but that’s just a bonus, because they are another invasive, exotic species.”

Volunteers, especially hardy souls associated with Mobile Baykeeper, worked diligently to scrape apple snail eggs from the shoreline. “It’s a very time-consuming job,” Ben groaned.  “We’re going to try a pressure washer next year!” He also discussed tentative plans to reduce the dense stands of emersed vegetation that provide excellent reproductive habitat for the exotic snails.

Summing it up, Ben said, “We got a lot of apple snails and made a really good dent in the population, but we going to continue trapping and compare numbers. “So far, pre-treatment rate was 222 snails and post was 32 snails.  A seven-fold decrease isn’t that bad. The bottom line is that we need adequate funding for next year.” Thanks for the update and all the hard work, Ben. The Mobile-Tensaw Delta is certainly worth the fight! Posted by Jess Van Dyke

For additional information, contact WFF Biologist Ben Ricks by phone at (251)-626-5153, or by email, ben.ricks@dcnr.alabama.gov

Video of Lagan Pond from WPMI Ch 15 Mobile:

http://www.mefeedia.com/news/24108642

Image of trap from Press-Register, Bill Starling photographer


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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