Feeding ecology of invasive Perccottus glenii (Perciformes, Odontobutidae) in Slovakia

Abstract

Stomach contents of 331 specimens of <I>Perccottus glenii (Perciformes: Odontobutidae</I>) were analysed. Chironomids and ephemeropterans dominated the diet of all size classes of fish; however, the frequency of crustaceans was also high. Micro-crustaceans (ostracods, copepods and cladocerans) dominated in lower size classes (20–39 mm); macro-crustaceans <I>(Isopoda, Amphipoda</I>) dominated in higher size classes (up to 79 mm). The proportion of crustaceans decreased from the size class 80–89 mm. With the increasing size of fish the frequency of molluscs (<I>Gastropoda</I>) increased, the maximum was in size class 70–79 mm. Cannibalism occurred from 60 mm, and it was significant from 80 mm. The highly mobile invertebrates (<I>Coleoptera, Heteroptera</I>) were found in the largest size classes. In middle size classes (40–59 mm), the widest spectrum of prey units was documented; the food variability of small (90 mm) individuals was poor. Differences in the diet composition of small individuals were negligible; the diet of the largest ones differed significantly. According to diet, two feeding size class groups were recognised: the first