W

ater pollution in Lake Maninjau in West Sumatra has worsened as the local administration continues to allow poor fish-breeding practices in the area.

More than 17,000 fish farm floating cages, locally known as keramba, operate on the lake despite a study by the Agam regency administration claiming that it can only support 6,000 cages.

The lake’s condition began to deteriorate after 600 tons of fish died throughout August and September last year. The breeders did not treat fish carcasses properly, consequently fostering green algae, which has heavily affected its waters ever since.

A fishery expert from Padang-based Bung Hatta University, Hafrijal Syandri, said he was worried that drought would occur this year and would lead to the algae further blooming.

“A similar massive algae bloom occurred in 2000, where the whole of the lake’s surface was covered with phytoplankton, 5 to 10 centimeters deep,” he told The Jakarta Post on Thursday.

Mass fish deaths in the lake have been a regular occurrence in the last 15 years, with over-farming generally blamed. In January last year, storms led to the deaths of two tons of fish and destroyed many cages, releasing a further 100 tons. Last year, three separate incidents saw between 5 and 80 tons of fish dying.

Thousands of cages, nonetheless, still continue to be found on the lake.

A 5-by-5-meter cage can house up to 4,000 small fish and can produce 750 kilograms per harvest. One cage of fish requires a ton of food per month.

Overpopulation threatens the lake’s ecosystem, including eight types of endemic fish species.

The lake’s issues also could potentially disrupt electricity in the region as it also hosts a hydropower plant.

Environment and Forestry Minister Siti Nurbaya Bakar visited the lake in January and later ordered the Agam regent to ban fish breeding in its waters.

If the algae clogs the lake, the only way to save it is to connect the lake with a flowing water source such as a rainfall or open stream from nearby rivers.

Agam Environmental Agency head Yulnasri said the local administration was working to restore the lake’s condition.

“We are trying to find alternatives for residents, so that everyone doesn’t need to rely on fish breeding activities for their livelihoods,” he said.

Most of the fish cages do not belong to the residents.

The owners, predominantly from North Sumatra, Riau and Bukittinggi in West Sumatra, hire local workers to man their keramba.

However, as none of them hold business permits, the regency administration earns nothing from the business.

The local authority’s attempts to curb the industry, however, have been met with resistance from local residents.

Another step that the administration is preparing is to clear away fish food that has already contaminated the bottom of the lake.

“Rp 1.2 trillion will be needed to do the cleaning. The central government should help us,” said Yulnasri.