Diversity and utilization of freshwater prawns (Macrobrachium) in river Cauvery in Tamil Nadu

River Cauvery, one of the perennial rivers of southern India, originates in Talakaveri, Brahmagiri Hills (12°25'N & 75°34'E) of the Western Ghats, in Coorg District of Karnataka and flows eastwards through Tamil Nadu into Bay of Bengal Sea.It runs a distance of 1171km with many contributories and tributaries.The major reservoir of river Cauvery in Tamil Nadu is Mettur Dam, where from water is usually released for irrigation from July to January.Due to minimum water flow from March to June the river bed between the river Anicut to the tail end zone gradually dries up leading to mass mortality of Macrobrachium species (Mariappan & Balasundaram, 1999).In this study, the freshwater prawn distribution in river Cauvery was studied from Mettur, Jedarpalayam, Grand Anicut and Lower Anicut, and Muthupettai in river Koraiyaru, a tributary of Cauvery.Among these, Lower Anicut is the main collection center for juveniles of Macrobrachium malcolmsonii, where the Tamil Nadu State Fisheries Department has the sole authority for the collection and sale of prawn seeds during monsoon.Farmers from the entire state come here to purchase juveniles for prawn farming from October to January.