Small fish (Leucaspius delineatus) that are often released into garden ponds and amphibian breeding sites prey on eggs and tadpoles of the common frog (Rana temporaria)

Abstract

Abstract Non-native fish often negatively affect amphibian populations. The sunbleak (Leucaspius delineatus), a small cyprinid fish, is often released into ponds that support amphibian populations because it is thought not to consume amphibian larvae; the argument was based on diet analyses. Here, we present results from a laboratory experiment that demonstrates that sunbleak consume amphibian eggs and larvae. Mortality of eggs and small tadpoles was 100%. Thus, sunbleak at least potentially could be harmful to amphibian populations despite their preference for small prey items reported in the literature. Although diet analyses are valuable, the assessment of whether a species is a predator of another should not be based solely on diet analyses. Experimental predation trials are necessary to assess predation risk.