The trophic niches of fish species from the Neajlov River Basin: dietary diversity assessment

This study analyzes, based on stomach content data, the trophic spectra of eight freshwater fish species collected from the Neajlov River Basin. Prey items, primarily macroinvertebrates, were identified to the taxonomic group level. The food composition was assessed using abundance, frequency of occurrence, Shannon diversity (H), and Pielou’s evenness (J). Chironomidae (Diptera) was the most dominant prey taxa across most species, followed by Coleoptera, Diptera (indeterminate) and Baetidae (Ephemeroptera). Pseudorasbora parva, an invasive species in Romania, exhibited a significantly low trophic diversity (H = 0.23; J = 0.118), dominated almost exclusively by Chironomidae. However, this does not necessarily indicate a specialized feeding behavior, but rather reflects limited prey availability at the sampling site. Conversely, species like Squalius cephalus and Alburnus alburnus showed higher dietary diversity and more balanced prey distribution. The results offer insights into feeding strategies, interspecific trophic overlap, and highlight potential ecological impacts of non-native species in freshwater ecosystems.