The Hilsa Fish: Bengal's Beloved Ilish and the Ecology Behind India's Overfishing Crisis

The hilsa, Tenualosa ilisha, is an anadromous species: it spends most of its adult life in the Bay of Bengal and the coastal sea, then swims hundreds of kilometres upstream into freshwater rivers to spawn. This is the same biological strategy used by salmon, and it makes the hilsa acutely sensitive to everything that happens along the entire length of a river, not just the stretch where it's caught. A dam, a sand bar, a sewage discharge point, an industrial effluent pipe: any of these can interrupt the migration before the fish reaches its breeding ground. The hilsa doesn't get a second chance. If it can't reach the spawning site, it doesn't breed that season.

The Ganga, the Padma, the Brahmaputra, and the Hooghly are all traditional hilsa rivers. The Padma, now mostly in Bangladesh, remains the most productive, which is why Bangladeshi ilish commands a premium even in Kolkata's markets. On the Indian side, hilsa catches in the Hooghly have dropped sharply over the past three decades, according to data from the ICAR-Central Inland Fisheries Research Institute (CIFRI), which has tracked population trends in Indian freshwater systems since the 1970s. The fish didn't vanish because of one bad season. It vanished incrementally, catch by catch, as the river changed around it.

Hilsa migration in Indian rivers is tightly seasonal. The fish move upstream primarily during the monsoon months, between June and September, when river flow increases and water temperature drops slightly. This is also when they are at their fattiest, most flavourful, and most commercially valuable, which means the peak fishing season and the peak breeding migration happen at exactly the same time.

Fisheries researchers at CIFRI have documented that a significant proportion of hilsa caught during the monsoon run are pre-spawning females carrying eggs. Catching them before they spawn removes not just one fish but an entire cohort of the next generation. West Bengal's fisheries department has implemented seasonal bans on hilsa fishing during parts of the monsoon, and Bangladesh has done the same on the Padma with measurable results, Bangladesh's hilsa production rose substantially after the introduction of its 22-day annual ban on hilsa fishing during the peak spawning period. India's enforcement of equivalent protections has been inconsistent, particularly in the Hooghly basin where artisanal fishing communities depend on the monsoon catch for the bulk of their annual income.

The Bengali attachment to ilish is genuine and old. Rabindranath Tagore wrote about it. Wedding menus in Kolkata treat it as a near-mandatory item. The first hilsa of the monsoon season is bought at auction prices that make headlines. This cultural weight is real, but it has created a strange blind spot: the fish is loved as food and almost never discussed as a migratory species with specific ecological requirements.

Most consumers who will pay five hundred rupees for a single Padma ilish cannot say where the fish breeds, what river system it depends on, or why the Hooghly population collapsed. The love is for the fish on the plate. The river it came from is invisible. This isn't unique to Bengal, most food cultures have the same gap between the animal and its ecology, but the gap matters more for a species whose survival depends on human decisions about river management, dam construction, and fishing regulation.

The hilsa also has a size problem that goes largely unnoticed at the retail level. The fish reaches sexual maturity at around 23 centimetres. A large proportion of hilsa sold in Indian markets are juveniles caught before they have ever bred. The minimum legal size for hilsa sale in West Bengal is 23 centimetres, but enforcement at fish markets is irregular, and smaller fish are routinely sold without penalty.

Bangladesh's hilsa recovery is the clearest proof that the fish responds to protection when protection is real. The government there designated six hilsa sanctuaries along the Padma and Meghna river systems, banned fishing during spawning periods, and compensated artisanal fishers with alternative income support during the closed season. Between 2003 and 2019, Bangladesh's hilsa production more than doubled, from roughly 200,000 metric tonnes to over 500,000 metric tonnes annually, according to the Bangladesh Department of Fisheries.

India has the same fish in the same river system with a fraction of that recovery. The difference is not the ecology, it's the policy consistency and the willingness to compensate fishers for the income they lose during closed seasons. Without compensation, a seasonal ban is a ban that only the poorest fishing communities bear the cost of. Compliance collapses. The fish keeps disappearing.

There are smaller-scale successes on the Indian side. The Chilika Development Authority in Odisha has worked to protect hilsa in Chilika Lake, where the fish enters from the sea to breed in the brackish water. Catch data from Chilika shows population stabilisation in areas where fishing pressure was reduced. The model exists. The question is whether it gets applied at the scale the Hooghly and Ganga systems actually need.

The synthesis the conservation data keeps pointing to is this: the hilsa is not running out because Bengal loves it too much. It is running out because the love stops at the kitchen and never reaches the river. A fish that crosses three states and two countries in a single breeding cycle cannot be protected by sentiment. It needs the river kept open, the breeding window respected, and the juvenile fish left in the water long enough to matter.