This edited book is focused on SDG 14: life below water. This book covers all aspects of fish biotechnology and health management. A detailed description is provided of CRISPR Cas9 technology application in the development of superior variety of fish with better growth, disease resistance, etc., accompanied by numerous helpful photographs and schematic diagrams. In addition, recent developments in nanotechnology and its application in fisheries production enhancement have been discussed. Further, topics includes, probiotics, immunostimulants, fish genetic markers, bioremediation, metagenomics, transgenerational immune priming, application of cell culture in fisheries and nano-biosensor application on fish disease diagnosis, pollution monitoring, etc. are provided in details. . The book is helpful for researchers, teachers, students, farmers, and entrepreneurs in utilizing the knowledge on recent advancements in different aspects of fish genetics and biotechnology for future researchand aquaculture production enhancement.