ABSTRACT: T he ingestion of plastic fragments by 3 species of Gerreidae (Eugerres brasilianus, Eucinostomus melanopterus and Diapterus rhombeus) in a tropical estuary in Northeast Brazil was assessed for 3 different size classes corresponding to juveniles, sub-adults and adults. In all, 425 individuals were analysed. The gut contents of 13.4% of these individuals contained plastic debris. The only type of debris found was blue nylon fragments originating from ropes used in fishing. Artisanal fishing is the main local activity and was considered to represent the principal source of this marine debris. Significant differences in the number and weight of nylon fragments ingested were found between species and size classes. Moreover, a decrease in the weight of the gut contents was observed in the individuals that had ingested nylon fragments. In addition to the hypothesis that Gerreidae mistakenly identify nylon fragments as prey items, we propose 3 further possible pathways: (1) from fragments that the fishes’ prey have already ingested; (2) through ingestion of fragments along with sediment that is sucked in during feeding; and (3) through ingestion of organisms that have aggregated on fragments. KEY WORDS: Polyamide thread · Ontogenetic phase · Marine conservation · Plastic marine debris · Mojarra |