The introduced fish, rotan (Perccottus glenii), depresses populations of aquatic animals (macroinvertebrates, amphibians, and a fish)

The fish rotan (Perccottus gleniiDybowski) was accidentally introduced into European Russia from the Amur River basin. Rotan is capable of colonising small waterbodies – favourable breeding sites of native amphibians. To reveal its influence on the native aquatic fauna, monitoring of small waterbodies has been carried out since 1994 in the region of Lake Glubokoe Reserve (Moscow Province, Russia). The fish's diet includes a wide range of animal species of all trophic levels. Rotan considerably decreases the species richness of aquatic macroinvertebrates and larval amphibians. As a rule, most amphibian species (Triturus cristatus, T. vulgaris, Rana temporaria, R. arvalis, R. lessonae) and the fish Carassius carassius failed to breed successfully in ponds inhabited by rotan. In contrast, the toad Bufo bufo bred successfully in such sites because its larvae are distasteful to rotan. Rotan–amphibian interactions are discussed.