Against the Tide

October is poised to be a busy month. One puja after another, the sound of dhak booming in the alleys and ear canals, the smell of incense and flowers, feasting, gifting, lighting… Amidst such festivities and heightened activity, a precious population will retreat silently to the vast unknown.

Shoals of silvery hilsa that had swum upstream the last few months will leave the rivers and canals for their other home in the ocean, bidding us goodbye until next year. The hilsa or Tenualosa ilisha migrates twice a year — a majority swims upstream during the monsoons, while a smaller population does so in February-March. The hilsa is anadromous — meaning, it spends most of its life in saltwater but needs freshwater to spawn. Its eggs cannot survive in saline water.

But what if there were no goodbyes, no waiting. What if “next year” could be turned into “all year round”?

That scenario is quite possible, as the work of scientists at the ICAR-Central Inland Fisheries Research Institute in Barrackpore, or Cifri, seems to bear out. They have been rearing hilsa in ponds for the last some years, a project facilitated by Cifri director B.K. Das. “We are close to success,” Srikanta Samanta, principal investigator and head of divisions at Cifri, tells The Telegraph.

Now, hilsa lovers are rather blinkered about their fish. They have their pet theories about what makes the hilsa special. What of the time spent in the ocean? Or the sheer exercise of swimming against the flow? Try telling a hilsa lover that the variety raised in a pond tastes just as distinctive as its riverine counterpart — it would be most difficult to digest.

And therein lies the real catch, as scientists working on this project explain.

The idea of captive breeding of the species has been around in the scientific community for over 100 years. “The fish is capable of thriving well in confined waters and of even attaining full maturity,” writes Sundar Lal Hora in 1938 in Records of the Indian Museum, Vol XL, a zoological journal published by the Indian Museum in Calcutta between 1907 and 1962. Hora had done a detailed investigation of the presence of hilsa in “isolated tanks” of the Palta water treatment facility in Barrackpore in West Bengal. An eminent ichthyologist, he played a crucial role in fisheries research and development in the state.

“At Cifri, we have been researching ways and means for 30-40 years,” says Samanta.

The first major project in this regard was started in 2012; a joint effort of six institutes, including Visva-Bharati. R.K. Manna, who is principal scientist at Cifri, says, “Our aim is to collect hilsa from the river, acclimatise them in the pond, keep them there till they mature and release eggs, let the eggs fertilise and finally see to it that the baby hilsa starts and completes its own lifecycle. Naturally, there are bound to be problems in the proper functioning of this entire chain. Some of the issues were identified and resolved at that time.”

Then the funds dried up.

Asecond opportunity took off in March 2021, a three-year programme funded by the ICAR. It was a joint effort of scientists at Cifri, ICAR-Central Institute of Brackishwater Aquaculture or ICAR-CIBA, ICAR-Central Institute of Freshwater Aquaculture and ICAR-Central Institute of Fisheries Education.

“We collected small-sized hilsas, two to three months old, in winter and kept them in three different kinds of ponds with slightly varying water quality. These ponds are at Kolaghat, Rahara, Kakdwip and Kalyani,” says Samanta. The female fish did well, ate well, but their rate of growth was slow. Normally, a hilsa takes 1.5 to 2 years to mature and release eggs. He adds, “But those in our ponds weren’t maturing even after two years. We tried many things to overcome this.” The male fish, however, matured, releasing milt or fish semen during the breeding season.

The largest female fish netted from the Kakdwip site was 762 grams. This, when a fair-sized hilsa available in the market is anything between 1.5 and 2 kilograms.

To get a clearer picture, the scientists even conducted a sonogram of the ovarian system. This was done at Kolaghat. It revealed that the fish had achieved “gonadal maturity of stage 6”, with well-formed eggs. Stage 7 is when they release the eggs, while the 8th and final stage is termed “spent”, explains Samanta. After an “induced release”, the scientists fertilised the eggs in the laboratory. However, within three or four hours, the development process ceased.

Not many are aware of the last inch covered. “That’s because our aim is not fertilisation, but to have the young ones grow,” says Manna.

Samanta and his team are more than hopeful. “Some issues remain at the final stages, which we are yet to get to the bottom of,” he adds.

So what is keeping them from carrying on? “Lack of funding,” says Manna. There is no staff at the sites. Some fish remain in the ponds, but that’s about it. The scientists tell The Telegraph they are spending their own money to buy fish feed.

Compare and contrast, it took about 40 years for the captive breeding of salmon to be successful, as Manna points out. According to Samanta, “Any breeding-related project would require 10 to 15 years of work.”

All very well, but the moot question on every hilsa lover’s lips would be — how does this version taste?

Manna narrates a story about how at a tank in Kalyani some of the “cultivated hilsa” were dying. The caretakers caught and cooked them. “There is no problem with taste, Sir,” they pronounced with gusto.

Manna says, “You need to first know where the hilsa gets its taste from. That would be the fatty acids. The fish eats zooplankton, which undergoes biochemical processes resulting in fatty acids. The type and quantity of zooplankton may vary in pond water as compared to ocean water, but that can be adjusted. We had set up a unit at Kolaghat for producing this kind of feed.”

The scientists conducted an organoleptic test or a taste test too. “What is the point of this huge effort if the hilsa doesn’t taste like the hilsa?” says Debasis De, who is principal scientist and head of the Kakdwip Research Centre, ICAR-CIBA.

“We used the 9-point hedonic scale to mark the parameters — smell, taste, texture and overall. We invited 50 people — including fish sellers, government officials, small businessmen and students. On the table were shorshe ilish, bhaja and bhapa. The same person cooked the dishes twice — once with pond-bred hilsa or Sample A, and then with river hilsa or Sample B — using the same ingredients. Our test showed there was no significant difference between the two samples,” says De.

Ask Somnath Maji, who was among the 50 people that day, “So how...?” His reply, without waiting for the entire question, “There was no difference. Both tasted the same.”