An assessment of the introduced mosquitofish (Gambusia affinis holbrooki) as a predator of eggs, hatchlings and tadpoles of native and non-native anurans

Abstract

The introduced mosquitofish (Gambusia affinis holbrooki) is a pest species in Australia and has been implicated in the decline of populations of native fishes and anurans. However, few quantitative data exist regarding interactions between Gambusia and native aquatic fauna. We used replicated laboratory experiments to investigate predation by G. a. holbrooki on eggs, hatchlings and tadpoles of native (Limnodynastes ornatus) and non-native (Bufo marinus) anurans. Our aims were to determine (1) whether the susceptibility of anurans to predation by G. a. holbrooki changes during larval development, and (2) the potential for G. a. holbrooki as a predator of the introduced toad B. marinus. Gambusia were significant predators of all aquatic life-history stages of L. ornatus, but were significant predators of B. marinus only at the hatchling stage. When offered both species simultaneously, Gambusia consumed tadpoles of L. ornatus but avoided those of B. marinus. The differences between the responses of Gambusia to L. ornatus and B. marinus are probably due to differences in palatability and toxicity of eggs, hatchlings and tadpoles of these species. The results indicate that G. a. holbrooki is unlikely to significantly affect larval populations of B. marinus via predation. However, Gambusia has the potential to significantly affect larval populations of L. ornatus in natural water bodies where these species co-occur.