Millions of fish died in Toba lake in Indonesia

Fish Kill Alert

Millions of fish in floating cages died suddenly this week in Lake Toba, the biggest lake in Indonesia.

E. Naibaho, a local aquafarmer, noticed the fish in his floating pens moving in an odd manner in the days leading up to the incident. The water had become cloudy as well.

When he and his workers went to feed the fish on the morning of Aug. 24, none of them could be seen rising to the surface. They tried adding oxygen to the water, but it didn’t work. Before the long the fish began floating to the surface, dead.

“My capital is gone,” Naibaho said. “Hundreds of millions of rupiah.”

Another farmer, M. Nadeak, estimated the total losses for all the farmers at 5 billion rupiah ($342,000). “Our economy is disturbed,” he said. “That’s going to create social problems.”

It was the second mass fish kill in as many years in the lake, which is located in North Sumatra. In 2016, millions of fish also turned up dead. Researchers attributed that incident to a sudden depletion of oxygen in the water, the result of a buildup of pollutants in the lake, unfavorable weather conditions and unsustainable practices by local aquafarmers.

Where the 2016 incident was concentrated in Haranggaol Bay of Lake Toba, this one happened in Pintusona, just off the giant island of Samosir in the center of the lake.

Other Indonesian lakes have experienced mass fish kills, too. In 2016, 3,000 tons of fish died suddenly in Lake Maninjau, West Sumatra — twice as many as that year’s incident in Lake Toba.

Both Toba and Maninjau are among the 17 lakes classified by the Indonesian government as being in “critical” condition, meaning they suffer from a host of environmental problems. Last year, government officials and academics from around the country gathered in Jakarta, the capital, to declare that a national body should be created to direct attention and funds to the nation’s more than 800 lakes.

Courtesy of


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