Differential effects of Bluegill Sunfish (Lepomis macrochirus) on two fish-tolerant species of tadpoles (Anaxyrus americanus and Lithobates catesbeianus)

Abstract

Amphibians can be partitioned among ponds based on their ability to tolerate fish predation. However, even among fish-tolerant species susceptibility to fish predators varies, with consequences for both prey and predator. We examined the effects of Bluegill (Lepomis macrochirus) and tadpole density on two fish-tolerant species of tadpoles (American Toad, Anaxyrus americanus; American Bullfrog, Lithobates catesbeianus). For A. americanus, Bluegill presence decreased survivorship, whereas in L. catesbeianus, survivorship was higher with Bluegill. Growth of neither species was affected by Bluegill. In A. americanus, development increased with initial tadpole density with Bluegill, but decreased with initial tadpole density in the absence of Bluegill. Anaxyrus americanus were less active with Bluegill. Bluegill grew faster with initial A. americanus tadpole density, but showed no change in growth with initial L. catesbeianus tadpole density. There was more periphyton present at the end of both experiments in mesocosms with Bluegill, and periphyton decreased with increasing tadpole density at a faster rate in the presence of A. americanus tadpoles compared to L. catesbeianus tadpoles. Our results show that not all fish-tolerant species of anurans are affected in the same way by fish predators, with potential consequences for the anurans, fish predator, and the broader aquatic community.