The goal of the book Fish Biology and Fisheries is to help integrate the study of fish biology with the study of fisheries. One might not expect these two subjects to need further integration. However, strong declines in many fish stocks around the world, combined with growing concerns about the impact of fisheries on marine and freshwater biodiversity, are raising new questions about aspects of fish biology that have traditionally dwelt outside mainstream fisheries research. Fisheries form an important sector of the country's economy in terms of food supply, employment, income and foreign exchange earnings. Fishes are one of the important sources of cheap protein food for the people and millions of fishermen and several industries depend on this source. Lack of a comprehensive treatise on the biology of fishes has prompted this humble piece of work leading to Essentials of Fish Biology. A wide coverage of fish biology will make it of interest not only to ichthyologist but to professional fishery biologist as well desiring to learn basic structure and function of fish body in daily life of the fish. This is an ideal textbook of fish biology which will serve as valuable work for undergraduates and graduates looking for a comprehensive source on a wide variety of topics in fish Biology and Fisheries.