Role of habitat complexity in predator–prey dynamics between an introduced fish and larval Long-toed Salamanders (Ambystoma macrodactylum)

Predation by nonnative fishes has reduced abundance and increased extinction risk for amphibian populations worldwide. Although rare, fish and palatable amphibians have been observed to coexist where aquatic vegetation and structural complexity provide suitable refugia. We examined whether larval Long-toed Salamanders (Ambystoma macrodactylum Baird, 1850) increased use of vegetation cover in lakes with trout and whether adding vegetation structure could reduce predation risk and nonconsumptive effects (NCEs), such as reductions in body size and delayed metamorphosis. We compared use of vegetation cover by larval salamanders in lakes with and without trout and conducted a field experiment to investigate the influence of added vegetation structure on salamander body morphology and life history. The probability of catching salamanders in traps in lakes with trout was positively correlated with the proportion of submerged vegetation and surface cover. Growth rates of salamanders in enclosureswith trout cues decreased asmuch as 85% and the probability ofmetamorphosis decreased by 56%.We did not find evidence that adding vegetation reduced NCEs in experimental enclosures, but salamanders in lakes with trout used more highly vegetated areas, which suggests that adding vegetation structure at the scale of the whole lake may facilitate coexistence between salamanders and introduced trout.