Salmon juveniles are vulnerable to predation by invasive African clawed frogs in Washington state

The Pacific Northwest, U.S.A. hosts multiple threatened salmonid species. Predation by introduced species are among the threats salmon face. African clawed frogs (ACF; Xenopus laevis,(Daudin, 1802) ) are a generalist, non-native invasive species recently found in waterways in Washington State, USA. Our goal was to identify if ACF posed a threat to early life stages of Chinook (Oncorhynchus tshawytscha, (Walbaum in Artedi, 1792)), coho (Oncorhynchus kisutch,(Walbaum, 1792)), and chum (Oncorhynchus keta,(Walbaum in Artedi, 1792)) salmon. We conducted feeding trials to discover the foraging propensity of ACF on salmon in three development phases, eyed eggs, alevin, and fry. We predicted that ACF would most readily consume less mobile life stages, based on foraging in other amphibians. Our results showed that ACF consumed all species at all juvenile life stages. The life stage experiencing the highest rates of consumption was salmon fry (72% consumption) and the lowest was eyed eggs (24% consumption). Gravel shelter minimally buffered ACF consumption. Given the growing presence of ACF in proximity to salmon spawning waterways, ACF may pose an additional threat to salmonid recruitment, and require further study to investigate potential interactions.