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Has global warming killed off the fish in Africa's deepest lake?

Andrew McConnell | robertharding | Getty Images

Global warming has hit fish numbers in Lake Tanganyika, one of the world's largest and deepest lakes, according to a new study.

The study, published online in the Proceedings of the National Academy of Sciences, found that the lake began warming in the 1800s, around the same time that the numbers of fish began to decrease. Commercial fishing on a large scale began at Lake Tanganyika in the 1950s.

"Some people say the problem for the Lake Tanganyika fishery is 'too many fishing boats,' but our work shows the decline in fish has been going on since the 19th century," Andrew S. Cohen, a distinguished professor of geosciences at the University of Arizona (UA), said in a news release.

According to the Lake Tanganyika Authority (LTA) around 1,500 species live in the lake, which holds nearly 17 percent of the planet's available surface freshwater supply. The lake is crucial in terms of supplying sustenance to people living in the region.

Overfishing was also acknowledged as being a factor in less fish being caught, UA said, but this needed to be considered alongside the issue of algae – which is a food source for fish in the lake – reducing as temperatures warm.

"We're showing the rising temperatures and declines in fish food are resulting in a decrease in fish production–less fish for someone to eat. It's a food security finding," Cohen said.

"We know this warming is going on in other lakes," he said. "It has important implications for food and for ecosystems changing rapidly. We think that Lake Tanganyika is a bellwether for this process."