In the decade that fisherman Edward Njeleza has been trawling the deep, clear waters of Lake Malawi in Africa’s Great Rift Valley, he has seen his once abundant catch shrink by 90 percent.

Now he spends most days on the shore searching for pods and a special type of grass he uses to make necklaces, key rings and bracelets to supplement his income.

In the past, he and his nine fishing mates would on average catch roughly 300 kilograms of fish a day, but that haul has dropped to no more than 25 kilograms, he told AFP.

“We go fishing but never come back with much,” said Njeleza, waiting by the lake with a bag full of homemade jewellery slung over his shoulder.

“And we don’t catch big fish.”

Lake Malawi, one of the deepest in the world, is estimated to have the largest concentration of freshwater fish species — up to 1,000, according to the UN Scientific and Cultural Organization (UNESCO).

And a local favorite, the Oreochromis lidole or “chambo” as it is known in this landlocked southeast Africa state where it is a vital source of protein for millions of poor, is among the hardest hit.

In its last study on chambo, the International Union for the Conservation of Nature estimated in 2004 that the population had declined 70 percent over the previous 10 years, William Darwall, head of the IUCN’s freshwater biodiversity unit, told AFP.

Overfishing is the main cause, and scientists blame both a lack of government muscle to enforce seasonal fishing bans as well as environmental degradation.

“The primary reasons why the fish stocks, specifically chambo, are going down is overfishing, and degradation issues because of factors related to the effects of climate change,” said William Chadza, director of the Center for Environmental Policy and Advocacy in Blantyre, the country’s finance and commerce hub.

Climate change is said to have affected rainfall patterns and caused a drop in the lake’s water levels, also hit by the effects of deforestation on tributaries feeding the lake.