Clinostomum sp. is a digenea Trematode can cause Clinostomiasis in fish (yellow grubs), with protrusions of yellowish metacercariae found in the fish body, gills, and visceral organs. This research was conducted in March to August 2024 at the Laboratory of Fish Parasites and Diseases, Faculty of Fisheries and Marine, Riau University.The aim of the study was to analyze the structure of liver and…