Nigeria, Nov. 26 -- As a boy in the 1970s, Mathew Osaronwaji often led groups of children down to Nsisioken, a cool, winding stream that flowed through Agbi Ogale, a community in Nigeria's oil-rich Rivers State.

At 15, he was already skilled with nets and hooks, catching shrimps, catfish, bonga shad, tilapia, and even electric fish.

"The harvest was always bountiful," he recalled. "It was a source of protein and a means of livelihood for our families."

Back then, the waters of Ogale, part of Ogoniland, teemed with life. The community hosted a yearly fishing festival where children from neighbouring villages competed to fill their baskets first. Then, it wasn't unusual for a single family to haul in 100 kilograms of fish in a day. Those...