Ichthyology is a branch of zoology which is concerned with the study of fishes, their biology, structure, organs and discovering their species. It includes species like chondrichthyes the cartilaginous fish, jawless fish i.e. agnatha, and bony fish i.e osteichthyes. There are approximately 33,400 species of fishes being studied under ichthyology. The book aims to shed light on some of the unexplored aspects of this field. Such selected concepts that redefine ichthyology have been presented in this text. It unfolds the innovative aspects of this area which will be crucial for the holistic understanding of the subject matter. Those in search of information to further their knowledge will be greatly assisted by this textbook.