Coastal ecosystems are not simply geographic locations proximate to the World’s Oceans. But, they are the arrangement of complex, diverse and fragile ecosystems unique in nature. Coastal ecosystems such as mangroves, coral reefs, backwaters, estuaries, lagoons and sea grass beds, besides performing crucial coastal protection functions, provide rich breeding and spawning grounds for fishes. 24618 species of known fishes belonging to 4258 genera in 482 families under 57 orders have been listed by Nelson (1994) from world waters. Of this, 131 species of Elasmobranches belonging to 67 genera in 28 families under 10 orders and 2415 species of Teleosts belonging to 902 genera in 226 families under 30 orders have been listed by Alfred et al (1998) from Indian waters. This book describes the taxonomic features of 256 species of fin fishes belonging to 141 genera, 84 families and 19 orders with colour photographs collected from the coastal water of Great Nicobar Biosphere Reserve, East coast of India. The taxonomic key presented in this book make the user to identify the specimen very easiy. Many new distributional records of fishes in Indian Ocean also documented here.