Microplastic contamination in wild freshwater fish: Global trends, challenges and perspectives

Abstract

Microplastics (MPs) are emerging contaminants of global concern with potential risks to wildlife and human health. This study reviewed the literature on MP contamination in wild freshwater fish, analyzing 144 articles published since 2016. Studies were conducted in 45 countries, mainly by China (8.97 %), Bangladesh and India (8.28 % each), and Indonesia (6.90 %). Cypriniformes were the most studied order (52.08 %), with rivers being the predominant sampling sites (57.64 %). Omnivorous fish (80.55 %) were the most studied, and MPs were found in the gastrointestinal tract (51.10 %), gills (19.38 %), and muscle (10.57 %). A total of 450 fish species were found to be contaminated by MPs, including 35 listed on the IUCN Red List: 2 critically endangered, 8 endangered, 12 vulnerable, and 13 near threatened. Although the representativeness of the data may be compromised by selective sampling, polymers such as PE and PP predominated, typically in the form of blue fibers ranging from 0.1 to 0.5 mm, indicating recurring contamination patterns in freshwater environments. Significant research gaps remain, including the need for standardized methods, broader inclusion of Neotropical fish species, investigation of biological responses, and studies on trophic transfer and biomagnification.