Abstract
In the present study, the aim was the quantitative and qualitative analysis of macroinvertebrates from the stomach content of the Squalius cephalus population living in the Oituz River basin. The stomach contents were investigated using a binocular stereomicroscope and the macroinvertebrates were identified to the smallest possible taxon. In the stomach of 60 specimens of Squalius cephalus, 10 macroinvertebrate groups were identified with 184 specimens. Among the macroinvertebrate groups identified, Coleoptera and Nematoda were the most common, with 75% and 36.6%, respectively. The highest dominance index was calculated for the Coleoptera group with 60.68% followed by Nematoda with 28.8%. In 14 of these 60 stomachs, we found fish remains, represented by: scales, vertebrae, radii, heads, and even larger pieces of undigested or digested fish. In addition to these, we also identified: feathers, plant fibers, pebbles, fat drops, and microplastics. In the stomachs of the 60 specimens of chub, we identified 124 microplastics in the form of microfibers of different colors and sizes: 42 purple, 38 blue, 19 red, 13 black, and 12 brown. This material's widespread occurrence and ingestion indicate that future research is needed for an ample range of species and habitats to fully establish the potential effects of microplastics in the aquatic environment.