The life cycle of Indian shad resembles to American shad, Alosa sapidissima (Bhuyan & Talbot, 1968). It has also some similarities with European shads, Alosa alosa (Allis shad) and Alosa fallax (Twaite shad). After spawning in freshwater, they return to the sea where they remain until the next breeding season. However, this life cycle pattern is not followed by all stocks/races of the species; some do not migrate from the sea to the river or vice versa (Blaber, et al., 2003). Hilsa spawn in fresh water and deposit eggs demersal. The eggs hatch after 23-26 hours at an average temperature of 23o C (Jones & Menon, 1951). The size of the hatchlings varies between 2.3 and 3.1 mm (Kulkarni, 1950; Motwani et al., 1957; Karamchandani, 1961). When the larvae can swim, they try to find suitable nursery grounds, normally in the lower region of the rivers or in coastal waters. In Bangladesh, this juvenile hilsa in the nursery ground are called Jatka (Rahman & Haldar, 1998). The Jatka resembles to adult Indian river shad (Gudusia chapra, Hamilton-Buchanan, 1822), which is locally called Chapila, and many fishermen and many consumers generally refer to Jatka as Chapila in the market (Mazid, 1994; Rahman, 1997). Hora & Nair (1940a) described the historical information on Jatka and confirmed that it is the young of hilsa. Using molecular genetic technology, Rahman & Naevdal (1998) confirmed that Jatka is the offspring of hilsa by comparing genotype and genotype distributions with previous analysis of hilsa. The Jatka remain around the nursery grounds for about 5-6 months and attain a maximum size of 15-16 cm (Raja, 1985; Mazid & Islam, 1991), but with a dominant size of 10-12 cm (BFRI/RS, 1994; Rahman & Haldar, 1998). However, Hossain (1975) reported that when Jatka become larger than 7 cm they may migrate to the deeper parts of the river, and finally when they reach about 12 cm they disappear from the river. Gradually the Jatka acquire the ability to tolerate saline water and move downstream to the estuary. There they spend their young life stages in brackish water. Later, the young move offshore for feeding and grow to adult size. After maturation, the adults again migrate upstream for spawning following the same pattern. The life cycle of Indian shad resembles to American shad, Alosa sapidissima. It has also some similarity with European shads, Alosa alosa (Allis shad) and Alosa fallax (Twaite shad) (Aprahamian, 1982; Bristow, 1992). After spawning in fresh water, they return to the sea where they remain until the next breeding season. However, this life cycle pattern is not followed by all stocks/races of the species; some do not migrate from the sea to the river or vice versa (Blaber, et al., 2003). Hilsa spawn in fresh water and deposit eggs demersal. The eggs hatch after 23-26 hours at an average temperature of 23o C (Jones & Menon, 1951). The size of the hatchlings varies between 2.3 and 3.1 mm. When the larvae can swim, they try to find suitable nursery grounds, normally in the lower region of the rivers or in coastal waters. In Bangladesh, this juvenile hilsa in the nursery ground are called Jatka (Rahman & Haldar, 1998). The Jatka resembles to adult Indian river shad (Gudusia chapra, Hamilton-Buchanan, 1822), which is locally called Chapila, and many fishermen and many consumers generally refer to Jatka as Chapila in the market (Mazid, 1994; Rahman, 1997). Hora & Nair (1940a) described the historical information on Jatka and confirmed that it is the young of hilsa. Using molecular genetic technology, Rahman & Naevdal (1998) confirmed that Jatka is the offspring of hilsa by comparing genotype and genotype distributions with previous analysis of hilsa. The Jatka remain around the nursery grounds for about 5-6 months and attain a maximum size of 15-16 cm, but with a dominant size of 10-12 cm (BFRI/RS, 1994; Rahman & Haldar, 1998). However, Hossain (1975) reported that when Jatka become larger than 7 cm they may migrate to the deeper parts of the river, and finally when they reach about 12 cm they disappear from the river. Gradually the Jatka acquire the ability to tolerate saline water and move downstream to the estuary. There they spend their young life stages in brackish water. Later, the young move offshore for feeding and grow to adult size. After maturation, the adults again migrate upstream for spawning following the same pattern. The life cycle of Indian shad resembles to American shad, Alosa sapidissima (Bhuyan & Talbot, 1968). It has also some similarities with European shads, Alosa alosa (Allis shad) and Alosa fallax (Twaite shad) (Aprahamian, 1982; Bristow, 1992). After spawning in freshwater, they return to the sea where they remain until the next breeding season. However, this life cycle pattern is not followed by all stocks/races of the species; some do not migrate from the sea to the river or vice versa (Blaber, et al., 2003). Hilsa spawn in fresh water and deposit eggs demersal. The eggs hatch after 23-26 hours at an average temperature of 23o C. The size of the hatchlings varies between 2.3 and 3.1 mm (Kulkarni, 1950; Motwani et al., 1957; Karamchandani, 1961). When the larvae can swim, they try to find suitable nursery grounds, normally in the lower region of the rivers or in coastal waters. In Bangladesh, this juvenile hilsa in the nursery ground are called Jatka (Rahman & Haldar, 1998). The Jatka resembles to adult Indian river shad, which is locally called Chapila, and many fishermen and many consumers generally refer to Jatka as Chapila in the market (Mazid, 1994; Rahman, 1997). Hora & Nair (1940a) described the historical information on Jatka and confirmed that it is the young of hilsa. Using molecular genetic technology, Rahman & Naevdal (1998) confirmed that Jatka is the offspring of hilsa by comparing genotype and genotype distributions with previous analysis of hilsa. The Jatka remain around the nursery grounds for about 5-6 months and attain a maximum size of 15-16 cm (Raja, 1985; Mazid & Islam, 1991), but with a dominant size of 10-12 cm (BFRI/RS, 1994; Rahman & Haldar, 1998). However, Hossain (1975) reported that when Jatka become larger than 7 cm they may migrate to the deeper parts of the river, and finally when they reach about 12 cm they disappear from the river. Gradually the Jatka acquire the ability to tolerate saline water and move downstream to the estuary. There they spend their young life stages in brackish water. Later, the young move offshore for feeding and grow to adult size. After maturation, the adults again migrate upstream for spawning following the same pattern.Like American shad, the Indian shad is generally termed anadromous, but it is diadromous, as it migrates frequently between fresh water and the sea. The adults migrate upstream to spawn at the start of the south-west monsoon and associated flooding of the rivers. During the peak breeding season the adult fish run in shoals to the estuaries and the rivers and may migrate upstream as much as 1200 km (usually 50-100 km) for spawning (Pillay & Rosa, 1963; Mazid, 1994; Rahman, 1997; FishBase, 2004). However, all races/stocks of hilsa do not migrate following the same pattern (Blaber, et al., 2003). In the northern Indian Ocean there are some purely riverine stocks, anadromous stocks which migrate between the sea and the river (the river-ward migration is for spawning) and purely marine stock (BOBP, 1987). As the most important stocks/races of the species is the anadromous type, most attention has focused on this group. During the last two decades natural migratory patterns of fishes have been heavily interrupted by the construction of dams, barrages, dykes, regulators, fences for flood control and irrigation or fishing purposes, without any provision for the passage of fish (Ghosh, 1987; Kowtal, 1994). Al-Nasiri & Al- Mukhtar (1988) reported that water pollution in Basrah, Iraq affected the hilsa stocks remarkably. The construction of the Farakka Barrage on the Ganga in 1972 has impacted on hilsa migration and hence its abundance further upstream. The Ukai and Kakrapara dams in Gujarat similarly affected migration of hilsa in the Tapti River of India (Pisolkav, 1994; Dubey, 1994). Due to the construction of obstructions and dams in the Kumar, Nabaganga and Feni rivers in Bangladesh, hilsa fishery in these rivers has been lost (Haldar & Rahman, 1998). Although migration of hilsa is restricted by barrages, it still runs far up the Ganges (FishBase, 2004). Many researchers have identified barriers to hilsa migrationas a major factor contributing to the decline of the species.