Chordata:Pisces

Introduction: Fishes are cold-blooded aquatic vertebrates that breathe through pharyngeal gills, propelling and balancing themselves using fins.Fishes, in simple definition, are aquatic vertebrates that have gills throughout life and limbs, if any, in the shape of fins.Among vertebrates, "fishes" constitute an amazing group that exhibits remarkable morphological diversity, inhabiting habitats and biology.Fishes have existed for more than 450 million years, during which time they have evolved repeatedly to fit into almost every conceivable type of aquatic habitat.Some fish, like lungfish, are of zoological importance because of their discontinuous distribution and anatomical features.They also play an essential role in the aquatic ecosystem.Many fish species are of immense aquaculture importance.Fishes constitute over one-half of the world's living vertebrates.The freshwater habitat comprises only a tiny proportion of the earth's surface water but contains an inappropriately large number of the world's fish species (Nelson et al., 2016).India is blessed with a rich fish biodiversity in its inland and marine waters, with a high percentage of endemic species (Gopi et al., 2017).It is blessed with rich biodiversity because of its tri-junctional position with the biogeographic realms, viz., Palaearctic, Afro-Tropical and Oriental.India is endowed with diverse habitats of aquatic systems: rivers, canals, estuaries, natural and man-made lakes, backwaters, brackish-water impoundments, marshes and mangrove wetlands.As regards the marine environment, India has over 11,098.8km long coastline and 2.3 million sq.km of Exclusive Economic Zone (EEZ) with four major coral reef island groups, viz., Andaman and Nicobar, Gulf of Mannar, Gulf of Kutch and Lakshadweep.The Indian Peninsula is also flanked by two large marine ecosystems, the Arabian Sea and the Bay of Bengal, which merge with the Indian Ocean around the southernmost extremity of India (Talwar & Jhingran, 1991;Mishra et al., 2013). Global diversity:A total of 37,102 fish species belonging to 5285 genera are distributed globally.Of these, 18,962 are found in freshwater (Fricke et al., 2025). Diversity in India:India is home to 3,919 fish species, which belong to 1,207 genera, 286 families and 57 orders.Of these species, 1,075 are found in freshwater.Below is a systematic checklist of the fish species of India, following the classification of Van der Laan et al. (2025). Diversity in StatesSl. No. State / Union Territory No. of Species No. of Endemic Species Andhra Pradesh 956Arunachal Pradesh