Global Warming

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

Clmiate change may have been the key cause of the decline of fisheries in east Africa's Lake Tanganyika rather than just overfishing, a new study has found.

The lake's fish are a critical part of the diet of neighbouring countries, Burundi, the Democratic Republic of Congo, Tanzania and Zambia, providing up to 60 percent of the animal protein consumed in the region and it also is an important biodiversity hotspot.

There have been growing concerns about the impact of overfishing, land use changes and changes in climate on this key ecosystem.

But the study by the US's National Academy of Sciences shows that the abundance of fish began declining in the 1800s when the lake's temperature began increasing.

Large-scale commercial fishing in the area did not start until the 1950s, so that is why the rising surface temperature is more likely to blame for the decline in fish productivity.

What we're seeing on the lake now, the fishermen are starting to catch juveniles and, once you start to catch juveniles, the fish population will start to decrease very dramatically and so in a relatively short time period, we could end up with fish stocks that, through a combination of overfishing and this climate change impact, could become very small.

The stratification of the lake has something to do with oxygen concentration that the fish need and so as the stratification moves up and down in the lake, the size of the lake obviously changes as well and so does the amount of oxygen-rich water for the fish."

As a result, fewer nutrients from the bottom reach the top, making less algae, which serve as food for the fishes.