Protocols of Fish Biology is a comprehensive book specifically designed to meet the Model Curricular requirements of students studying at the UG and PG levels, as well as aspirants preparing for UGC-NET, various certificate, diploma, and degree vocational courses, CSIR-NET, and similar examinations. The book is divided into six units and 47 chapters that cover all aspects of ichthyology, including distribution, evolution, and adaptation, characteristics, classification, physiology, and economic importance of fish. The book provides current information and advancements on the scheme of classification given by Nelson (2016), genomics, and the effects of climate change on fish. Each chapter is labeled with appropriate headings and subheadings in bold.From the majestic migrations of ocean wanderers to the intricate social structures of freshwater communities, this book delves into the fascinating tapestry of fish biology. The book demonstrates the authors extensive knowledge, innovative ideas, and lucid style of explaining text clearly and systematically. This book may pique readers interest by transforming the ordinary into the extraordinary and mirroring the depths of knowledge with the ocean.