Kolkata: the city that eats fish reared on sewage

Editor/Mohamed Shihab

Farmers rear sewage-fed fish to meet the West Bengal city’s growing food demand in the face of competition for wastewater and real estate

It all started as an accident, if you believe the story that the fishermen of the east Kolkata wetlands tell.

Around a century ago, a cultivator named Bidu Sarkar accidentally allowed untreated wastewater from Kolkata’s sewage pipes into his fish pond. Realising what had happened, Sarkar expected disaster.

Instead of killing his fish, however, the water doubled his yields. When fishermen from the surrounding area came to find out more, they discovered that the combination of sewage in the water and sunshine broke down the effluent and allowed plankton, which fish feed on, to grow exponentially.

Soon thousands of fish farmers had set up bheris, or fishponds, across 12,500 hectares on the eastern fringes of the city.

Today, according to Dr Partha Prathim Chakrabarti, principal scientist at the Central Institute of Freshwater Aquaculture, the east Kolkata wetlands provide a living for some 50,000 cultivators and fish traders, most of them small-time private entrepreneurs who earn an income rearing 10,000 tonnes of wastewater-fed fish a year.

Despite occasional media scares about eating sewage-fed fish, Kolkata continues to depend on the practice for its food. “Sewage which is of domestic origin is usually free from hazardous chemicals harmful to human health,” says Dr Chakrabarti. “However, microbial populations contained in sewage need to be checked regularly.”

Kolkata’s municipality, according to government data (pdf), has the capacity to treat only 24% of the city’s 706m litres of wastewater produced each day. The rest comes here, where – unregulated – the city’s fishermen recycle it in their ponds.

“They just dump the water and we just use it,” says Sosi Dalal Ghosh, the owner of Nida Nagar Agro & Fisheries, one of the biggest companies producing fish in the area. “Thanks to private companies, the Kolkata municipal corporation has not had to spend anything to get its water treated, plus the people of Kolkata get to eat cheap fish, much cheaper than in Delhi or Mumbai, as using wastewater reduces our production costs.”

If the mere idea of the city’s fish swimming around in the city’s excrement doesn’t put you off your dinner, the smell at the wetlands will. Some workers cover their faces with cloths, others can be seen scrubbing themselves with sweet-smelling soaps after they finish a day’s shift.

But, though they may inspire disgust, these ponds have fed at least three generations of Kolkata’s citizens and the government has publicly stated that it expects such initiatives to help meet the country’s fish demand for years to come.

Threats to urban aquaculture

India is the world’s second largest farmed fish producing country in the world, after China, with an annual output of more than 10m metric tonnes of fish. Since the 1950s, thanks to a variety of government-backed schemes, the sector has increased 11-fold, and now contributes to 85% of India’s total fish production.

The Kolkata model of rearing sewage-fed fish is used in a number of Indian cities, including Nagpur, Chennai and Bhopal. In fact, Kolkata’s urban fish farming has become so famous as a potential solution for sustainable food production that some farmers, like Ghosh, now even work as consultants for PwC as foreign governments seek advice on how to set up similar aquaculture plants.

“They use this technique now in Bangladesh, Pakistan, Myanmar, Thailand and even Germany and France,” says Ghosh, delightedly.

Some of the fishermen who work at the east Kolkata wetlands are now third- or fourth-generation fish farmers, having inherited bheris from their grandfathers and fathers. Additional migrant workers from the impoverished nearby states of Uttar Pradesh and Bihar have been pulled in to meet the growing city’s burgeoning demand for fish, a staple in Bengali cuisine.

But competition for wastewater for the aquaculture and agriculture sectors, among others, is putting pressure on the industry. Ghosh explains that, with less water to share between the fish farmers, each bheri is getting shallower: “For good [fish] production, you need depth of around 5ft. Now the water is barely 2ft.” Another key challenge for the fish farmers is land availability. Industrialists trying to capitalise on cheap real estate just a few kilometres from the city have started encroaching on the wetlands, forcing fish farmers out. Despite the Ramsar convention, an intergovernmental treaty to conserve and promote the sustainable use of wetlands, a number of illegal constructions have appeared across the area.

With an entire city’s fish supply and sewage system, as well as thousands of jobs at stake, Kolkata’s municipal corporation is under increasing pressure to start regulating. In the meantime, Ghosh and his fellow fish farmers will continue with the day’s tasks. “If we stop working, how will Kolkata get fish?” he asks.

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