Assessment on Microplastics Contamination in Freshwater Fish: a Case Study of the Ubolratana Reservoir, Thailand

Microplastic pollution is now a global issue. Reservoirs are an enclosed aquatic environment at risk from accumulation of microplastics. Few studies have used fish species as bio-indicators to monitor microplastic contamination in reservoirs. Freshwater fish were caught by local fishermen from 10 stations around the Ubolratana Reservoir, Thailand in October 2018 and the abundance, size, color and shape of microplastic particles in their stomachs and intestines were investigated. Fourteen fish species were examined. Results showed that 96.4% of the fish had ingested microplastics at mean abundance of 2.921.30 particles per fish, with significant differences of abundance between species. Microplastic abundance was highest in carnivorous fish Parambassis siamensis (4.111.08 particles per fish). The most common size of ingested microplastics was over 0.5 mm (66.4%), with 51.0% as blue color and 98.2% fiber shaped. High levels of microplastics were ingested by fish located in the middle and lower parts of the reservoir. Results revealed that blue fiber microplastics dominantly observed in fish were derived from the breakdown of nets used for fishing activities.