This book offers a detailed examination of fish physiology, covering a range of topics including the evolutionary history of fish, the endocrine system, behavior, aquaculture, and future research. Chapters 1-4 cover the scope and definition of fish physiology, the impact of the endocrine system on fish, and various behaviors such as swimming and feeding. Chapter 4 focuses on the significance of fish physiology for successful aquaculture practices. Chapter 5 reviews the future of fish physiology and its emerging trends. This book is a useful resource for students, researchers, and professionals working with fish populations, aquaculture, and aquatic ecosystems.