Arguably, Hilsa is not just a tasty and healthy fish species that migrates from the sea up the river to spawn. It is a cultural icon that binds Bengalis, whether from West Bengal or Bangladesh, together in their shared love for Ilish Machch. Pohela Baishakh or the new year day’s meal is not complete without Ilish. Though Hilsa is celebrated fervently by the Bengalis, it is prized in all estuaries of South Asia, from Narmada, Mahanadi, Godavari, Cauvery to Indus and Irrawaddy and takes the name of Chaski, Palva, Ilishii, Palla, Pulasa, etc. It is also found at confluence of Tigris and Euprates in Iran, where it is as prized and known as Sbour. The fish flavours several poems, folklore, songs and phraseologies of the entire South Asia. In cultural terms, the significance of Hilsa is comparable only to Salmon and Mahseer.
Tenualosa ilisha, Hilsa or Indian Shad belongs to the sub family Alosinae of Family Clupeidae. Commercially, it is the most important fisheries in the estuaries, especially in the Ganga-Hooghly region.It occurs in marine, estuarine and riverine environments and is found in Indus of Pakistan, Irrawaddy of Myanmar and Indian rivers like Ganga, Bhagirathi, Hooghly, Rupanarayan, Brahmaputra, Godavari, Narmada, Cauvery, Tapti, coastal rivers like Padma, Jamuna, Meghana, Karnafuly and others in Bangladesh. It is seen to migrate up smaller estuaries like Pennar too.
Hilsa, by habitat, is a marine fish but migrates in estuaries and rivers for spawning, normally inhabiting the lower region of the estuaries and the foreshore areas of the sea. Hilsa ascends the rivers for spawning and the spent fish and their progeny migrate down the river towards lower estuaries and coastal areas, moving in shoals. The peak upstream migration of Hilsa in most of the rivers of the country is generally in the monsoons months of July and August and continues upto October or November. The spring spawners that enter the river for spawning in January-March return to the sea during July-August when these are caught in good numbers. The monsoon spawners that enter the river during September- October return to the sea after spawning and these spent fishes are caught in good numbers during January- March. Similarly, the off springs of spring-spawners make journey for the sea from the river during November- January, whereas the off springs of monsoon spawners return to the sea from the river during July- September. (Bhaumik et al, CIFRI, 2012)
Obstruction to undertaking this spawning migration by dams and barrages has been singled out as the primary reasons for the fall of Hilsa fisheries in India as well as Bangladesh. The trade of this commercially important fish species constitutes upto 1.5% of Bangaldesh’s National Gross Domestic Product and about 2 million fishers are estimated to depend on Hilsa fisheries in Gangetic estuaries. Till August 2014, Bangladesh has stopped Hilsa exports to India to contain astronomic price rises in Bangladesh as the costs of the fish are becoming uncontainable due to its cultural importance on one hand and dwindling supply on the other. India has requested Bangladesh to lift the ban of Hilsa export, but it is yet to relent, due to a number of socio-political reasons.