This book covers various aspects of fish health, disease identification and laboratory procedures. Each section of the book is detailed and includes practical information, step-by-step procedures and relevant illustrations and diagrams. The recent updates on fish disease diagnosis have been incorporated to address new techniques and technologies in the field. Fish disease diagnosis is primarily based on the color and characteristics in the image to target the infected area. It is an indispensable part of modern aquaculture, and rapid and real-time diagnosis is an essential part of the early and precise treatment of the diseases. As farmed fishes are affected by viruses, bacteria, parasites, metal pollution, and fishing damage, accurate disease diagnosis is crucial for effective management interventions. It often requires a combination of clinical expertise, advanced technology, and collaboration among healthcare professionals. This book is a comprehensive guide for students, researchers and professionals involved in fish disease diagnosis.