Sent to live on a remote island in the Tanzanian half of Lake Victoria, Mark Weston finds a community grappling with one of the world’s great unknown environmental crises.

You used to be able to stand on the beach and fish. In my father’s time you could catch them with your bare hands.

Lake Victoria was once one of the most biodiverse places on Earth, but a predator released into its waters by East Africa’s British colonisers has left a trail of destruction in its wake. The lives of millions of people have been upended, as a fateful confluence of overfishing, pollution and deforestation has triggered one of history’s greatest mass extinctions.

On remote Ukerewe Island, Mark Weston finds out how local communities are responding to the crisis. He lives for two years alongside the families and fishermen hardest hit by the upheaval and gets to know the aid workers, sorcerers and holy men whose businesses are booming.

A captivating blend of travel writing and environmental reportage, The Saviour Fish paints an intimate picture of rural Tanzanian life, and of the human cost of biodiversity loss.