Mali – which means “hippopotamus” in Bambara, one of a dozen local languages – is the largest country in West Africa, five times the size of Great Britain. Naturally wealthy in gold, its empire in its 14th-century heyday stretched across most of West Africa and boasted two great cultural, intellectual and financial centres: Timbuktu and Djenne. In the late 19th century it became a French colony, regaining its independence in 1960. Mali today is one of the poorest countries in the world, heavily reliant upon international aid and vulnerable to changes in the price of cotton, its main export.

Lake Antogo is near Bamba, about 120 miles from Timbuktu. The Dogon families who live in the 33 villages in the area are materially poor, though not entirely cut off from the outside world – many have access to a TV. They survive on an unchanging diet based on millet; only the rich can afford rice. The miracle of the fish is not just a cultural event, it is a rare feast. “It is an essential part of their year,” says Alain Buu, a French photojournalist who went to Mali to witness the “miracle” for himself. He drove 500 miles along dirt roads from Bamako, the capital, to see the event, and slept on the roofs of houses. The heat, which reached 50C in the daytime, was still stifling after dark. “There was no electricity, no air conditioning, no ice.”

Most of the country is desert; the Niger river is its lifeblood. After the rains have come, between June and September, the small tributaries of the river Niger join to form larger rivers. In the dry season, this evaporates into unconnected lakes and ponds, in which the catfish that were spawned in the river emerge. The other lakes are fished the year round, but Antogo has a particular significance. Legend has it that the lake was discovered in ancient times by a young girl from Bamba village. She told her sister in the neighbouring village of Yanda about the profusion of fish, and her brother-in-law claimed the lake for Yanda. But her father staked a claim on it too, and tribal war broke out. Eventually her father and his fellow tribesmen won the battle, and even today only Bamba men can take part in the great fishing ceremony; the men of Yanda are forbidden.

Buu has travelled in Senegal, Sudan and Ethiopia, but says this trip was particularly memorable. “It was amazing to see a thousand people barely clothed,” he says. He was struck by the intensity of the men’s determination. “This is not something put on for tourists. The men won’t move an inch to help you get a better picture if it interferes with what they’re doing.” It was a once-in-a-lifetime opportunity, and there were no second takes. “From when they started to go in, to when they were in the centre of the lake, I took four photos. That was it.”