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Indonesia investigates mass shark deaths at captive-breeding facility

  • An investigation is underway after 127 sharks died at a captive-breeding facility in a marine national park in Indonesia.
  • Experts suspect poor water quality may have triggered the die-off.
  • The breeding facility, operating since 1960 and a key attraction inside Karimunjawa National Park, was shut in June 2018 after a visitor swimming in one of the floating cages was bitten by a shark.

JAKARTA — Authorities in Indonesia have launched an investigation into the mass die-off of captive-bred sharks earlier this month at a facility in a marine national park off Java.

In all, 127 sharks were found dead March 7 in two floating net cages located off Menjangan Island in Karimunjawa National Park, as reported by Minarno, the owner of the Hiu Kencana captive-breeding facility. The sharks were identified as blacktip reef (Carcharhinus melanopterus) and whitetip reef sharks (Triaenodon obesus). Neither is considered a protected species under Indonesian law; both are categorized as “near threatened” on the IUCN Red List.

“I was dumbfounded by the mass death,” Minarno, who goes by one name, was quoted as saying by local media. “Some of the dead sharks had been bred for years.”

Minarno reported the shark deaths to local police and submitted four of the fish carcasses and water taken from the floating cages. He also sent samples for testing at the local aquaculture agency. Minarno said he incinerated the rest of the dead sharks.

Karimunjawa’s clear waters and scenic coral reefs make it popular among local and foreign divers and snorkelers. Image by Batara via Flickr (CC BY-NC-ND 2.0).

The facility had been closed since June 2018 by the agency that manages the national park, after a visitor was bitten by one of the sharks while swimming in the floating cage.

Experts have suggested this as a factor for the mass die-off, pointing to overpopulation and water pollution in the floating cages. Dharmadi, an expert at a government-run fisheries research agency, said waste from nearby factories might have polluted the water in the national park, raising concentrations of chemicals such as hydronium and cadmium, which can be lethal for marine life.

“The cause of death is most likely poor water quality, but this needs to be proven in the lab,” he told Mongabay-Indonesia.

The mass die-off was the first at the shark-breeding facility, which has been in operation since 1960, Minarno said. Some of the fish were brood stock, while the rest were captive-born individuals, he added. “These sharks were priceless to me,” he told news site Kompas.com.

Minarno said his shark captive-breeding program was a key attraction for tourists visiting the national park. “There are still baby sharks in a separate floating cage,” he said.

A blacktip reef shark. Image by Jan Derk via Wikimedia Commons (CC BY-SA 3.0).

Karimunjawa is one of seven marine national parks in Indonesia, and is renowned for its coral reefs, which include two protected types of coral: black coral (Antiphates sp.) and organ pipe coral (Tubipora musica). Nearly 500 species of reef fish thrive in the waters around Karimunjawa, and the park is a popular tourist attraction for divers and snorkelers from Indonesia and abroad.

Declared in 2001 as a marine reserve, the park spans 1,100 square kilometers (425 square miles) and encompasses 22 islands that are part of the Karimunjawa Archipelago. A patchwork of zoning policies allows artisanal fishing in certain areas, as well as tourism and research activities.

This story was first reported by Mongabay’s Indonesia team and published on our Indonesian site on March 21, 2019.

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