More than 60,000 penguins in colonies off the coast of South Africa have starved to death as a result of disappearing sardines, a new paper has found.

More than 95% of the African penguins in two of the most important breeding colonies, on Dassen Island and Robben Island, died between 2004 and 2012. The breeding penguins probably starved to death during the moulting period, according to the paper, which said the climate crisis and overfishing were driving declines.

The losses that researchers recorded in those colonies were not isolated, said the paper, which was published in Ostrich: Journal of African Ornithology. “These declines are mirrored elsewhere,” said Dr Richard Sherley, from the Centre for Ecology and Conservation at the University of Exeter. The African penguin species has undergone a population decline of nearly 80% in 30 years.

African penguins shed and replace their worn-out feathers every year to protect their insulation and waterproofing. However, during the moulting period, which takes about 21 days, they have to stay on land. To survive this fasting period, they need to fatten up beforehand. “If food is too hard to find before they moult or immediately afterwards, they will have insufficient reserves to survive the fast,” said Sherley. “We don’t find large rafts of carcasses – our sense is that they probably die at sea,” he said.

For every year except three since 2004, the biomass of the sardine species Sardinops sagax had fallen to 25% of its maximum abundance off the coast of western South Africa, the study found. The fish are a key food for African penguins. Changes in the temperature and salinity off the west coast of Africa have made the fishes’ spawning less successful. Levels of fishing, however, have remained high in the region.

In 2024, African penguins were classified as critically endangered, with fewer than 10,000 breeding pairs left.

More sustainable fisheries management could improve the penguins’ chances of survival. Conservationists are taking action on the ground, by building artificial nests to shelter chicks, managing predators and hand-rearing adults and chicks who need rescuing. Commercial purse-seine fishing, which involves encircling a school of fish with a large net and then trapping them by closing the bottom, has been banned around the six largest penguin-breeding colonies in South Africa.

It is hoped this will “increase access to prey for penguins at critical parts of their life cycle”, said the study co-author Dr Azwianewi Makhado, from the Department of Forestry, Fisheries and the Environment in South Africa.

Lorien Pichegru, a professor of marine biology at Nelson Mandela University in South Africa, who was not involved in the study, said the results were “extremely concerning” and highlighted decades-long mismanagement of small fish populations in South Africa. “The results of the study are only based on penguins’ survival until 2011, but the situation has not improved over time,” she said.

Pichegru said addressing extremely low levels of small fish stocks required urgent action, “not only for African penguins but also for other endemic species depending on these stocks”.

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