ichthyofauna, species richness, life strategies, trophic groups, aquatic ecosystem, small rivers
Abstract
This study conducted a comprehensive analysis of fish biodiversity in three tributaries of the middle reaches of the Horyn River (Ustia, Zamchysko, Stubelka) to assess the ecological state of small river ecosystems. During 2022–2024, 16 fish species belonging to 9 families and 5 orders were detected during controlled fishing, with the most diverse group (11 species) being Cypriniformes. The Zamchysko River showed the greatest species richness (15 species), while the Ustia River had only 8 species. Biodiversity indices (Shannon, Berger – Parker, Pielou) revealed significant differences between the studied rivers. The Zamchysko River demonstrated the highest diversity indicators (H'=2.49), indicating a balanced ecosystem with diverse habitats. The Stubelka River showed similar levels of diversity (H'=2.44), but with a noticeable dominance of Rutilus rutilus. The lowest values in the Estuary (H'=1.92) and high Berger – Parker index (d=0.29) indicate the dominance of Scardinius erythrophthalmus and a simplified structure of the ichthyocenosis.
Analysis of fish life strategies revealed the predominance of coastal species (48% in Ustia) and pelagic taxa (33% in Stubelka). The trophic structure was characterised by a high proportion of planktivorous (49–56%) and omnivorous species (20%), which indicates mesoeutrophic conditions. The limited number of benthic animals, in particular in the Ustia River (17%), indicates the degradation of benthic biotopes. The presence of predators (7–22%) confirms the stability of trophic chains in the Zamchysko and Stubelka rivers.
The results emphasise significant anthropogenic impacts (urbanisation, land reclamation, agriculture) on fish communities. The decline in biodiversity in the Ustia River correlates with hydrological changes and pollution. These findings provide valuable data for developing strategies for the conservation and restoration of small river ecosystems in the Horyn River Basin.
Author Biographies
О. О. Biedunkova, National University of Water and Environmental Engineering, Rivne
Doctor of Biological Science, Professor
I. I. Statnyk , National University of Water and Environmental Engineering, Rivne
Candidate of Agricultural Sciences (Ph.D.), Associate Professor
R. V. Levkivskyi, National University of Water and Environmental Engineering, Rivne
Post-graduate Student
V. V. Vechorka, Sumy National Agrarian University, Sumy
Doctor of Agricultural Sciences, Professor
O. H. Mykhalko, Sumy National Agrarian University, Sumy
