Invasive freshwater fishes often display high trophic plasticity, facilitating their establishment and persistence in novel environments. This study examined the feeding ecology, growth patterns, and trophic role of the invasive black bullhead Ameiurus melas in the eutrophic Gruža Reservoir (Central Serbia), with emphasis on ontogenetic dietary shifts and potential ecological impact. Diet composition was analyzed in 103 individuals representing three age classes using traditional diet indices, Costello graphical analysis, self-organizing maps (SOMs), and the Indicator Value (IndVal). Chironomidae, Protozoa, and fish eggs were the dominant dietary components across age classes, although their relative importance varied ontogenetically. Younger individuals exhibited a more generalized feeding strategy, whereas older fish showed increased specialization on benthic prey. SOM-IndVal analyses revealed prey taxa associated with specific feeding patterns at the individual level, identifying Diptera as an indicator prey not detected by population-level indices. Length–weight relationships indicated negative allometric growth (b < 3) across all age classes, consistent with a diet dominated by low-energy prey. These feeding patterns may contribute to altered benthic processes, reduced native fish recruitment, and reinforcement of eutrophic conditions. Overall, the results highlight the pronounced trophic flexibility and ecological plasticity of A. melas, supporting its invasive success in degraded freshwater ecosystems.
Radenković et al. (Fri,) studied this question.