The "Locusts of the Sea" Crown-of-Thorns Starfish Sweep Through Dongsha — Experts Warn: All Hard Coral Could Be Devoured Within Two and a Half Years

Full reprint from the Environmental Information Center: "The 'Locusts of the Sea' Crown-of-Thorns Starfish Sweep Through Dongsha — Experts Warn: All Hard Coral Could Be Devoured Within Two and a Half Years"

Dongsha Atoll National Park is facing a crown-of-thorns starfish (COTS) outbreak. Last year (2024), the Taiwan Coral Reef Society and the Marine National Park Section of the National Park Service assembled a team that removed nearly 14,000 crown-of-thorns starfish. This year (2025), the team has set out again, removing close to 34,000 individuals within a single month. Honorary Chairperson Cheng Ming-shiou of the Society warned that wherever the starfish pass it is like a wildfire sweeping through an underwater forest — healthy hard coral is devoured, disrupting the habitat of reef fish and other organisms and causing an ecological catastrophe. Without significantly intensified management, he estimates the coral reefs of the area could be stripped bare by these "locusts of the sea" within two years. He has called on the Executive Yuan to convene an inter-agency task force, and to commit more resources to scientific research and removal operations.

This Year's COTS "Army" Is Lining Up Directly on the Hard Coral Reef

Crown-of-thorns starfish have almost no natural predators and can only be removed by injecting diluted acetic acid. At a press conference held on the 8th, the Taiwan Coral Reef Society's Honorary Chairperson Cheng Ming-shiou stated that in 2024, a roughly 62.5-hectare area spanning the Blue Cave and the eastern section around the southwestern corner of Dongsha Atoll was estimated to harbour some 110,000 crown-of-thorns starfish. Between June and October, the team removed approximately 14,000. Photographs show that hard coral in the southwestern corner has been nearly completely killed, with algae now growing in the shallows.

From March to May this year, the team returned to Dongsha for another survey and found that crown-of-thorns starfish had massed in a roughly 1.6-hectare area extending 1.6 kilometres east of Blue Cave No. 2, with nearly 34,000 individuals removed within one month. Cheng Ming-shiou noted that during last year's removal operations, divers sometimes had to search carefully for starfish hiding out of sight — but this year, the crown-of-thorns starfish were essentially "lining up" to receive injections of acetic acid: "Their entire 'army' is right down there." The large aggregations consist predominantly of individuals over 40 cm across, described as being "in peak condition." Although more than 30,000 starfish have been removed in recent months, a population boom is expected as summer approaches — each female starfish can release up to 300 million eggs — making it critical to intensify removal efforts in May and June.

However, the method of injecting diluted acetic acid has its limitations. Divers cannot descend beyond 30 m, and the bottom time available at 20–30 m is very limited. Conducting research surveys on crown-of-thorns starfish at greater depths would require a substantially larger commitment of resources and personnel.

Dongsha Atoll's Hard Coral Could Be Completely Devoured Within Two and a Half Years

Coral reef ecosystems hold enormous economic value: abundant fish populations generate a spillover effect that boosts fishery yields in surrounding waters. Cheng Ming-shiou explained that if healthy hard coral is stripped bare and bleached, the marine ecosystem will be thrown severely out of balance, leading to significant economic losses as well. The countdown has already begun for Dongsha Atoll's coral ecosystem — he warned that without accelerated action, at the crown-of-thorns starfish's pace of "one kilometre per month," all hard coral in Dongsha Atoll could be devoured within two and a half years. Based on international precedents for coral reef damage compensation, the loss would amount to at least NT$33.5 billion.

Taiwan currently faces a shortage of personnel, vessels, and scientific research capacity when it comes to managing the crown-of-thorns starfish problem. Cheng Ming-shiou urged the government to adopt more proactive management measures, drawing on Australia's approach to COTS management, and called for the Executive Yuan's Policy Minister to convene and establish an inter-agency task force, with additional funding allocated for survey and removal operations.

In response, the Ocean Conservation Administration (OCA) told the Environmental Information Center that it cooperated with the National Park Service last year to remove crown-of-thorns starfish from Dongsha Atoll, sharing costs such as vessel services. It also mobilised the Dive Warriors, the Coral Special Dive Alliance, and its own staff to support removal operations, and is currently in discussions with the National Park Service about collaboration this year.

Beyond Dongsha, the OCA noted that in 2021 it cooperated with Academia Sinica to address a COTS outbreak in the waters surrounding Taiping Island in the South China Sea, removing a total of 941 crown-of-thorns starfish. Between 2022 and 2024, the island was visited four times, and 986 individuals were removed across 82 survey plots. The OCA encouraged members of the public who spot crown-of-thorns starfish around the main island or outlying islands to report sightings through the coral health reporting platform on the "iOcean Marine Conservation Network," enabling authorities to monitor COTS invasion status across different locations. Where large-scale outbreaks are confirmed, further investigation and removal will be carried out.

Further Reading

• Original article: The "Locusts of the Sea" Crown-of-Thorns Starfish Sweep Through Dongsha — Experts Warn: All Hard Coral Could Be Devoured Within Two and a Half Years
• Crown-of-Thorns Starfish Outbreak Kills Ninety Percent of Coral Reefs Around Taiping Island — Researcher: "I've Never Seen Anything This Devastating"
• A Spiny Visitor in Penghu Waters — Crown-of-Thorns Starfish Pack a Dangerous Punch
• 25 Years of Academic Research — Cheng Ming-shiou: Dongsha's Ecosystem Has Held On and Can Serve as a Marine Germplasm Repository