This textbook, entitled "Principles of Biochemistry: With Special Reference to Fishes", covers major aspects of biochemistry as per the UGC and ICAR prescribed syllabus. This book is written with an aim that it will act as a ready-reckoner in some important topics of Biochemistry. Of course there are many more topics in this subject, which could not be included in this volume. Those topics will be incorporated in future editions of this book. There are some variations in the biochemistry of fish from that of other vertebrates, which have been reported in a scattered manner. Such variations are mostly in fish muscles and hormones. I have tried to collect the most relevant informations and presented in this book for the benefit of students who study Fishery. This is the first textbook on Biochemistry in which emphasis has been given to Fishery Biochemistry along with the general aspects of Biochemistry. Thus this book will be useful for Fisheries as well as other branches of science students.