Inter- and intra-annual apple snail egg mass dynamics in a large southeastern US reservoir

The introduction and spread of non-native species represents a significant threat to freshwaters. Non-native Pomacea are a recent and detrimental gastropod invader, altering habitats, biodiversity, and ecological function. Despite large size, adult Pomacea spp. may be cryptic but their egg masses, which are species specific in color and size, appear useful in determining presence and spatial distribution within invaded areas. We used a combination of annual (2013-2016) and monthly (April 2016-March 2017) shoreline transect surveys to determine the distribution of Pomacea spp. egg masses, along with habitat and water quality data, in Lake Seminole, GA, USA. Surveys identified invasive P. maculata and native P. paludosa, and provided evidence for rapid dispersal of P. maculata. Egg masses of both species occupied a wide range of emergent surfaces across the lake. Physicochemical measures suggest elevated specific conductivity corresponds with Pomacea presence. Temperature correlated with monthly variation of egg mass; however, egg masses were observed at water temperatures of 11.3 A degrees C, below reported limits. Pomacea maculata dispersal throughout Lake Seminole is rapid, and shoreline classification and physicochemical conditions are influencing the on-going dispersal. Continued expansion of this invasive herbivore could have ecosystem-level consequences in Lake Seminole and other invaded waters across the southeast US.