Microplastics in different tissues of some commercially important fish species from Anzali Wetland in the Southwest Caspian Sea, Northern Iran

Abstract The aim of this study was to investigate the occurrence of microplastics (MPs) in the gastrointestinal (GI) tract, muscle and gonads of 193 individuals of nine commercially-important fish species from Anzali Wetland between May and July 2018. Tissues were removed, digested by 10% KOH for 24 h at 60 °C, filtered on cellulose nitrate filter and then dried. MPs were found in all tissues. There were significant differences between the numbers of isolated particles from GI tract and control groups (procedural blank containing Milli Q water without tissue), while their abundance in the muscle and gonads did not display significant differences with control groups. Higher abundances of MPs were recorded in omnivorous fish (2.26 ± 2.93 items/individual) than carnivorous species (1.10 ± 1.10 items/individual) (P