The textbook contains the basics of general parasitology, the order and description of all the main stages of the general parasitological study of fish, methods of studying the causative agents of protozoal diseases of fish, helminthiasis, crustaceoses, etc. Diseases of Fish. Methods of fixation and coloring of parasites are included , device and rules for working with a light microscope , List of necessary equipment, Rules for the selection of sick fish , pathological material , Blood , Feeds and Shipments for Laboratory Research, forms opened, form of the protocol of complete parasitological opening of fish , as well as recipes for fixers and dyes. The training manual is intended for full-time students in direction 35. 03. 08 “Water bioresources and aquaculture” .