The Florida apple snail (Pomacea paludosa) is a critical component of central- and south-Florida wetland food webs and its population dynamics are directly and indirectly influenced by environmental changes. Little is known about fish effects on apple snails. Our objective was to quantify and compare the effects of select native and non-native predator fishes on apple snail growth and survival. We tested the native predator Lepomis microlophus and the non-native predators Hemichromis letourneuxi and Cichlasoma urophthalmus. Heterandria formosa, a very small non-predatory native fish, was used as control. We set up 16 mesocosm tanks (with 306 L of water) that were stocked with hatchling, juvenile and adult apple snails. Adult and juvenile snails were individually marked so we could follow their growth through time. Tanks were spatially blocked and then assigned to treatments with either one predator fish (Lepomis, Hemichromis or Cichlasoma) or ten control fish (Heterandria) added to each tank. After three months in mesocosm tanks, we evaluated survival of snails, snail reproduction (number of eggs), snail and predator growth (through length and weight measurements), and damage to snails’ antenna.
Results/Conclusions
Survival of hatchling apple snails was lowest in the presence of the native predator L. microlophus and the non-native C. urophthalmus treatments, while antenna damage of adult and juvenile snails was greatest in the L. microlophus and H. letourneuxi treatments. Growth of juvenile snails was lowest in the L. microlophus treatment. Our results show that apple snails are negatively affected by both native and non-native fish predators. Negative impacts of these fishes on hatchling, juvenile, and adult apple snails demonstrate how broad the damage caused by fish can be. The results suggest that the addition of introduced predators to Florida wetland habitats compound the effects of native fishes by creating additional predation pressure and harassment.