Pilot testing and protocol development of giant applesnail suppression at Mandalay National Wildlife Refuge, Louisiana—July–October 2017

This report provides an overview of the pilot study and description of the techniques developed for a future mitigation study of Pomacea maculata (giant applesnail) at the U.S. Fish and Wildlife Service Mandalay National Wildlife Refuge, Louisiana (MNWR). Egg mass suppression is a potential strategy for the mitigation of the invasive giant applesnail. In previous studies at Langan Municipal Park in Mobile, Alabama (LMP), and National Park Service Jean Lafitte National Park-Barataria Unit, Louisiana (JLNP), we determined that spraying food-grade oil (coconut oil or Pam™ spray) on egg masses significantly reduced egg hatching. At JLNP we also developed methods to estimate snail population size. The purpose of this pilot study was to adapt techniques developed for previous studies to the circumstances of MNWR in preparation for a larger experiment whereby we will test the effectiveness of egg mass suppression as an applesnail mitigation tool. We selected four canals that will be used as treatment and control sites for the experiment (two each). We established that an efficient way to destroy egg masses is to knock them down with a high-velocity stream of water pumped directly from the canal. The traps used at JLNP had to be modified to accommodate the greater range of water-level fluctuation at MNWR. One of the three marking methods used at JLNP was selected for use at MNWR.