Assessment of microplastic contamination in fish from the Sutlej River, India

Aim: To evaluate the occurrence and distribution of microplastics (MPs) in non-edible tissues (gills and digestive tract) and edible tissue (muscle) of Labeo rohita, Cyprinus carpio and Wallago attu. Methodology: Fish specimens were collected bimonthly from October 2024 to March 2025 from the Phillaur and Walipur Kalan stretches of Sutlej River. The collected samples were subsequently processed and analyzed by following the standardized protocol of National Oceanic and Atmospheric Administration (NOAA). Results: Majority of MPs were detected in the intestine (48.0%) and gills (40.4%), whereas lower proportion was found in the muscle tissues (11.6%). The highest level of MP contamination was recorded in W. attu collected from Wallipur Kalan, followed by L. rohita and C. carpio which exhibited moderate levels of contamination. Among different MP shape, fibers were most abundant (58.36%), followed by films (24.21%) and fragments (13.2%). Regarding size distribution, 0.1-0.5 mm MPs were the most prevalent (30.87%), followed by 0.5-1 mm size category (25.18%). In terms of colour, blue MPs were the most abundant (35.48%), followed by transparent (26.33%) and red particles (15.01%). Surface morphological analysis of MPs using field emission scanning electron microscopy (FE-SEM) revealed characteristic weathering features including pits, grooves and cracks. Interpretation: Present findings confirm that widespread occurrence of MPs in commercially important freshwater fish species from the Sutlej River, indicating contamination arising due to anthropogenic activities include direct discharge of plastic waste from industries and domestic source. This highlights the need for improved plastic waste management practices and reduced plastic utilization to mitigate MP pollution in fresh water ecosystems.