Posts Tagged 'copper'

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

Captain Copper

Captain TrialSince 1994, SePRO Corporation has been an innovative leader in aquatic plant management. After turning the tide against highly-invasive hydrilla (Hydrilla verticillata), SePRO’s flagship product, “Sonar” (fluridone), became the world’s leading brand of aquatic herbicides. David Tarver was a big part of that success. For over 30 years, I have known David and found him to be an excellent source of information on aquatic resource management. That is why, when he asked me to test four of SePRO’s chelated copper products (“K-Tea,” “Nautique,” “Komeen,” and “Captain”) on Pomacea insularum, I was flattered and excited. I promised speedy, conclusive results. How hard could it be? And so, the adventure began.

Bench tests are inexpensive, repeatable, and fairly reliable, though efficacy is always better in a container than in the environment. One simply places the test organisms in identical containers with identical volumes of water, varies the rate of the test chemical, waits 48 or 96 hours, and determines mortality. If, say, a fish rolls over, flairs its opercula, and no longer moves with eyes bulging, it is safe to say that the concentration of test chemical is lethal. Simultaneously, if fish are thriving in the “control” container with no test chemical added and in containers with lower concentrations, the lethal rate can be determined. No problem. Bring on the snails!

Of course, life is full of surprises. Unlike fish and other aquatic organisms, apple snails can present a number of unique challenges to the researcher. First, like fish, Pomacea also have an operculum, but it is not a bony flap protecting the gills; it is a well-sealed “trap door” that chemicals cannot penetrate. Secondly, Pomacea are amphibious, not aquatic. If an apple snail detects a toxic chemical, it can simply crawl out of the test solution. Thirdly, Pomacea are strong enough to push the tops off of containers and crawl away. Finally, a dead apple snail with its operculum closed looks exactly like a live one for many days. As I told David, those are the reasons (excuses?) a simple experiment took me 9 months and 14 trials!

From the first four trials in the fall, it became clear that “Captain” had an edge on the other products that couldn’t be explained by the concentrations of the active ingredient, as metallic copper: Captain (9.1%), Nautique (9.1%), Komeen (8.0%), and K-Tea (8.0%). So, as winter approached, all I had to do was focus on one product, determine the lethal rate, repeat the trial a few times, and report the results. It seemed simple, until I realized that water temperature played a key role in efficacy. At 20o C, all test animals survived, but all died (except control animals) when an identical test was repeated at 28o C. Obviously, the lethal effects of copper to Pomacea are directly related to metabolic rate, but in a greenhouse with only partial control of temperature, precisely repeating bench tests proved impossible.

I did come away with some tentative, experimental results that are worth reporting, however. First, as mentioned above, I suggest using “Captain” to control exotic apple snails. Perhaps, it is the “double chelation” that makes it more lethal by keeping it in solution longer, but it stands above the rest. Secondly, treat when water temperatures are warm (>270 C or 800 F). Of course, that will require more caution regarding non-target damage, i.e. “fish kills.” Third, because Pomacea can completely “clam up” for at least 24 hours, split treatments make sense. Fourth, coordinate physical removal with treatments, if practical. The snails should become vulnerable to hand-picking, as they move to areas shallow enough to extend their snorkels or to even leave the water.

What about the rate? The maximum label for “Captain” is 1.0 ppm (A.I.) or 3 gallons/ac-ft. (see below), but Pomacea insularum were vulnerable at much lower rates. In fact, higher rates may be counter-productive in that snails tended to close their opercula. At 230 C, the snails produced mucus at 0.2 ppm and, at 0.4 ppm, they lay on the sides with opercula open. After 96 hours, 0.4 ppm was lethal at that cooler temperature. At 270 C, 0.2 ppm was lethal after 48 hours. As mentioned earlier, bench test tend to over-estimate toxicity compared to the natural environment. Therefore, if you want to play hard-ball with exotic apple snails, treat with “Captain” at 0.3 to 0.5 ppm A.I. twice, 24 to 48 hours apart.

I am concerned about presenting these tentative results. Someone needs to fund Dr. Linda Nelson at USACOE/WES to conduct more detailed and controlled time/concentration research on chelated copper and exotic apple snails (Hint: SePRO). In any case, “Captain” appears to be your best bet, but carefully read the label. I hope to be able to try this product in the field soon and will report back on the results. My last suggestion is to read my earlier post about copper, entitled “The Copper Question.” It is dangerous to fish, if not used carefully, and is rather non-selective in terms of invertebrates. The environmentally sound way to use copper is seldom. Posted by Jess Van Dyke 

P.S. I have no relationship with SePRO, financial or otherwise. My thoughts are my own. You are responsible for the careful use of any pesticide.

Label for “Captain”: http://www.sepro.com/documents/Captain_Label.pdf

SePRO Corporation: www.sepro.com

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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