Physical-chemical and biologicaldiversity of streams are influenced by the land use in their watersheds. Plastics currently make up the most important waste asset, representing an important part of the transported and accumulated material in water courses. This work analyzes the consumption of plastics debris by the fish communities in streams with two contrasting types of land use. We worked with threestreams impacted by urbanization and threeby extensive ranching. The stomach and intestinal contents of 309 individuals of 29 species were analyzed, by a modified alkaline digestion, and observed under a stereo microscope with polarized light. A total of 373 plastic itemswere found, of which the majority corresponded to fibers (318). A significant difference was found between the percentage of individuals that consumed plastic debrisbetween both systems (51.6% in ranchers and 76.6% in urban, p = 0.014 Mood’s Median), but no difference was found in the average ingested per individual. This study establishes the first baseline on plastic debris consumption by fish in Uruguayan streams, showing the extent of the plastic and microplastic pollution problem. Although there are differences between the analyzed sites, we also observed significant contamination in streams far from urbanization.

The widespread use of plastic products in our modern life represents a serious threat to aquatic environments and wild animals that are exposed to plastic waste. Although microplastics (MPs) have been reported in fish from several freshwater environments around the world, mountain environments have been little studied so far. The occurrence of MPs was assessed in the gastrointestinal tracts (GITs) of non-native (rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta) and native (torrent catfish Hatcheria macraei) fish from the Mendoza River in the Central Andes, Argentina. Fibers (85%) were the main MPs type recovered from the fish here analyzed, followed by fragments (15%). Blue fibers were the main type of MPs in analyzed specimens: brown trout (50%), rainbow trout (71%), and torrent catfish (63%). Significant differences in the median total MPs’ abundance and median total fiber abundance were observed among fish species. The highest MPs’ abundance was found in the GITs of brown trout followed by rainbow trout, while the lowest was found in the GITs of torrent catfish. This study represents a baseline for the occurrence and characteristics in terms of shape and color of MPs in freshwater fish collected from a mountain river of the Central Andes.