Posts Tagged 'traps'

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)

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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

The Copper Question

copper-question

If one word could characterize Drew Leslie’s long, exemplary, and largely unheralded career in biology with the State of Florida, it would be “objectivity.” He is a precise, well-documented, unemotional thinker. That’s why, when he has a scientific opinion, it’s best to listen carefully. Drew doesn’t like the use of copper in the aquatic environment.

I remember the day in 1988, when he started down that path of reasoning. As Department of Natural Resources’ research biologists, Drew and I were conducting a herbicide study in the Basin of the St. Marks River, using various rates of chelated copper  (4-10 gal Komeen/acre) in test plots on exotic Brazilian Elodea (Egeria densa), when up came hundreds of native apple snails (Pomacea paludosa) and other native snails, as well.  In Florida, non-target damage to native plants related to a herbicide treatment was, and is, considered a mistake, but killing non-target animals is more like a serious blunder.

Drew was alarmed considering that copper was one of the most commonly used aquatic herbicides in the U.S. He began an extensive literature search on the impact of copper on aquatic organisms, leading to two watershed documents, “Aquatic Use of Copper-Based Herbicides in Florida” (Leslie, 1990) and “Copper Herbicide Use-Patterns in Florida Waters” (Leslie, 1992). In his reports, Drew made persuasive arguments that “copper is the most toxic herbicide to non-target organisms labeled for use in Florida waters” and that copper “treatments performed repeatedly . . .  can potentially add significant quantities of copper to the sediments.” Subsequently, the annual use of copper in the State funded program has dropped 99.6% from 31,612 lbs (A.I.)/ year (1985-1987) to 138 lbs/ year (2007).

 

Of course, the wisdom of restricting the aquatic use of copper is much less clear now that invasive snails threaten the ecology of Florida’s waterways. The good news is that copper can kill Pomacea insularum, is relatively inexpensive, safe to humans, and labeled for aquatic use by the EPA (though only one product by Chem One is labeled specifically for snails). The bad news is that repeated use of copper will change an aquatic ecosystem to something more akin to a swimming pool in terms of zooplankton and benthic organisms. Is there some rational, middle ground where copper is used to initially knock down the invasive, snail population to the point that the remainder can be effectively trapped?

Bruce Jaggers (FWCC) and the folks at St. Johns River Water Management District have been heroically battling the Island Apple Snail in Newnans Lake (7427 acres), south of Gainesville, Florida. This FWCC Fish Management Area is part of the Orange Creek Basin, which includes Paynes Praire State Park, Orange and Lochloosa lakes, the Lower Ocklawaha River, and the Lower St. Johns River. Under the guidance of Dr. Bill Haller (IFAS), multiple, copper sulfate treatments reduced egg production from 100-200 clusters/month in the small, infested area to “a dozen or so” per month last year. That’s not eradication, though. 

In a recent email, Bruce writes, “FWCC has informed me that we will not be participating in copper treatments anymore, citing a previous agreement with DEP to not use copper for aquatic plant control.  We used 2 tons of copper in our last treatment at Newnans Lake, and I think that made Tallahassee feel quite uncomfortable, particularly with no guarantees.” That position is certainly understandable, but Pomacea insularum still threatens the entire Orange Creek Basin.

In response to Bruce’s email, I offered to give him some of our apple snail traps and bait to try in Newnans Lake, writing, “I would love it if you would try a few of our traps where you last observed egg masses. You may have a very small population that is vulnerable to trapping after aestivation but prior to egg laying.” In return, I asked for a thorough, scientific evaluation of the traps with recommendations for improvements. I hope he accepts! Posted by Jess Van Dyke

Aquatic Use of Copper-Based Herbicides in Florida (Leslie, 1990): http://www.myfwc.com/nonnatives/InvasivePlants/docs/copper.pdf

Copper Herbicide Use-Patterns in Florida Waters (Leslie, 1992):

http://dep.state.fl.us/lands/invaspec/2ndlevpgs/pdfs/cuconfnc.pdf

 


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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