Coastal Aquaculture and Mariculture

Unit 1 - Fishery Zones and Fishery resources

1.1. Introduction
Almost all natural bodies of water bear fish life, the exceptions being very hot thermal ponds and extremely salt-alkaline lakes such as the Dead Sea and Great Salt Lake. The fishes belong to the most numerous and diversified group among vertebrates. They dominate the water bodies of the world through a variety of morphological, physiological and behavioral adaptations. They have been in existence for more than 450 million years. A total of 24618 species of fishes belonging to 482 families and 4258 genera have so far been described. About 58% of the fish species are marine while 41% are freshwater inhabitants and 1% migrants. In our Indian region alone, there are 2,500 species of which 930 are inhabitants of freshwater and the rest live in the seas. In other words, India harbours 11.5% of the fish fauna so far known in the world. There are over 800 living species of sharks and rays, 30 species of chimaeras and ratfishes, 6 species of lung fishes, 1 species of coelacanths, 36 species of long ray finned bichirs, sturgeons and paddlefishes. The Neopterygii are the rest of the known species of modem fishes. All these fishes inhabit various niches in the aquatic environment. The diversified habitats of fishes include open oceans, deep oceanic trenches, nearshore waters, saline coastal embayments, brackishwaters, estuaries, intermittent streams, tiny desert springs, vernal pools, cold mountain streams, lakes, ponds, etc.