Image copyright Daniela Sala

Fifty years ago, the river Tiber in Rome was home to dozens of eel catchers, but now there is just one - Cesare Bergamini is the last professional eel fisherman on the river.

From his battered red dinghy, Cesare Bergamini waves and points at his wrist. It's 07:00 - time to go out and check on his 250 eel nets - and I've kept him waiting.

I follow the dirt road down to the river bank, leaving behind the soundtrack of Rome's busy ring road, and cross the wooden passage that links his mooring to dry land. It is cluttered with old pictures, stacks of nets and metal scales - Cesare's life at a glance.

Once I'm on board, the speedy red boat cuts through the green waters. "I know every inch of the river," Cesare says. "If someone analyses my blood, they'll find river water inside. It's true.

"I've swept up and down the Tiber, and by exploring it I found the place with more fish. Here it comes up from the sea and I catch it. Then, when it comes down to return to the sea, I fish the second round."

After a few kilometres, Cesare stops the boat and starts pulling in the conical nets one by one, in a long and rhythmic process. The 74-year-old is tireless, and his gestures follow a precise routine.

Image copyright Daniela Sala

The river has been his passion since 1947, when he was seven. Cesare and his older brother Alfredo would stay with their grandparents after school, and their grandfather, also an eel fisherman, would take them out on his boat. "I became fond of fishing and I fell in love with the river. Nobody can take it away from me, not even if they pay me," Cesare says.

In post-war Italy, eels were plentiful and sold for 600 lire per kilo - accounting for inflation that's the equivalent of about 8 euros (£6, $10) today. Cesare still earns between 7 euros and 9 euros per kilo, but the difference is in the quantity of fish he catches - there are far fewer eels in the river these days. "Nobody today wants to do this job," he says. "It's too hard and not profitable."

He steers the boat to show me some pipes dumping wastewater from the local sewage treatment plant into the river. "Mankind destroys things. Laws exist and are right, but man acts the opposite way, destroying nature."

About 75% of the water samples taken in the Lazio region in 2014 contained concentrations of bacteria above the legally prescribed level, according to a survey by the environmental association, Legambiente. Despite the pollution, there has never been a ban on fishing in the Tiber delta.

The European eel

Image copyright Thinkstock

Eels come to Europe from the Sargasso Sea, in the North Atlantic ocean, where they return at the end of their life to spawn

Depending on their maturity, eels are known as glass, elvers, yellow and silver eels.

The European eel is now classed as a critically endangered species

"Years ago they started using hydrochloric acid and chlorine to clean the water, killing the microorganisms eaten by the fish. The colour now is good, but the eels can't find anything to eat," says Cesare.

He has a solution to that problem though: he swiftly pulls up a net to reveal clusters of beige marbles lining the ropes. "Snails," he says, looking at my surprised face. "Eels love them. I buy sacks of snails from the farmers nearby."

While most people have turned their backs on the profession, Cesare continues eel fishing as before, partly to survive and partly to maintain his family's and the region's traditions. When his brother Alfredo quit recently because of poor health, a new sidekick joined Cesare - his stepson from Ukraine, a young man in his twenties. He's a useful helper, even though he speaks no Italian.

Image copyright Alessia Cerantola

Sometimes cars from the ring road overhead end up in the river and Cesare is called on to help the police. "Oh, yes, it happens. Some people die or are in trouble," he says. "I love to rescue people. I feel human and I want to help everybody, without reward. Whenever someone asks my help, I do my best."

The road, called the Gran Raccordo Anulare, or Gra, is notorious for its gridlocks. Those who live along this 70km circular traffic jam were recently the subject of a documentary film, Sacro Gra (a pun on the Holy Grail) which scooped the Golden Lion at the Venice Film Festival in 2013 - the first documentary ever to win it.

Cesare was one of the stars of the film. People said it would change him, but he only cares about the river. "They told me: 'You're going to change, you're becoming an actor.' I said: 'No, I'm staying on the water. For me the river is life.'"

As the dinghy docks, Alfredo, now 77, runs over to help his brother bring in the catch. A cat begs for its share of the small fish trapped in the nets.

Image copyright Daniela Sala

The fish are weighed then sold to a transporter who delivers them to restaurants and eel farms in northern Italy every Saturday.

The morning has yielded a few hundred kilos of eels. "It was good, yes, good," says Cesare - but he knows that making a living from fishing alone is hard, and that the younger generation couldn't manage it. He doubts he will pass on his trade to anyone else.

The fishermen from the boathouse across the river gave up when they became too old to continue. They were lucky to find a Bangladeshi immigrant willing to take on the business - he catches other kinds of fish.

Image copyright Daniela Sala

The river system is fairly unregulated, a freedom that benefits the remaining fishermen - however the resulting pollution affects them badly. For the past 10 years, the Bergamini brothers have shared their knowledge of the river and its fauna with the University of Tor Vergata in Rome.

"They've always been aware of the fish resources, especially the eels," says Eleonora Ciccotti, senior researcher at the university and head of a project that monitors the region. "They have witnessed all kinds of things over the years. They are the last fishermen so intimately connected to the Tiber."

Cesare is determined to go on. "As long as I am able to move, I'll stay on the water. And if I can't move, I'll ask somebody to carry me here," he says. "If I'm not here, I'll die. Sunday is a holiday. But I prefer to come to work."

Eel on the menu

Image copyright Getty Images

Yellow eels are called "ciriole" in the Roman dialect. Ciriole is also the name of a bread, whose shape resembles the fish. In Rome eels are traditionally prepared with peas and tomato sauce, and often eaten at Christmas or New Year. Hot-smoked eel is popular in Northern Europe, while jellied eels are a typical treat in the East End of London.

However, there are serious concerns surrounding the sustainability of eels. The Marine Conservation Society advises people to avoid eating eels as no sustainable source is yet available.

Image copyright Daniela Sala

Cesare Bergamini spoke to Outlook on the BBC World Service. Listen again on iPlayer or get the Outlook podcast.

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