Effectiveness of a Hand Removal Program for Management of Nonindigenous Apple Snails in an Urban Pond

Abstract

Introduced applesnails (Ampullariidae: Pomacea) have been responsible for crop and habitat damage in freshwater systems around the world. Two Pomacea species known to damage aquatic vegetation, P. maculata (Island Apple Snail) and P. canaliculata (Channeled Apple Snail), have been introduced into Florida. This investigation was conducted to evaluate efficacy of a hand-removal program for the management of nonindigenous Pomacea in a small (1.62 ha), relatively isolated urban pond. We removed snails and egg masses from the pond by hand at pre-determined time intervals during May 2008—June 2011. We made a total of 107 collections; 21,343 snails and 20,244 egg masses were removed during the study period with >90% of both removed during the first year (20,961 and 18,934, respectively). Snail densities were reduced in the wadeable near-shore habitat from 1–3/m2 to <0.001/m2. The total cost of the project (salary, supplies, travel) was $10,475. At the time of the final collection in year 3, we observed no snails and removed only two egg masses. Four followup assessments September 2011—May 2012 indicated that the hand-removal program was successful and snails had been nearly eradicated from the site. Occasional connections with a population occupying an adjacent drainage ditch could result in a future re-colonization of the pond. Compared with chemical methods, control was achieved with lower monetary cost and less ecological risk. Further evaluations of this method will be necessary to apply it or use it in larger connected ecosystems.