Acanthaster: what is the status of the vinegar fight on the Great Barrier Reef?

Nearly 1.4 million crown-of-thorns starfish removed from the Great Barrier Reef since 2012. The figure comes from the Australian Marine Park Authority (GBRMPA), on a page updated March 26, 2026. And the basic tool fits in a syringe.

A single injection of household vinegar or bovine bile salts is enough to kill the starfish. The previous version of this article, published in 2023, still presented the method as a curiosity and described the animal as an invasive species. Each figure has been reviewed.

Here is the current status of the program, what the studies from James Cook University (JCU) really say, and what you can do if you dive on an affected reef.

Where does the crown-of-thorns control program stand in 2026?

The crown-of-thorns control program (COTS Control Program) has been running since 2012 on the Great Barrier Reef. As of March 26, 2026, GBRMPA reports nearly 1.4 million starfish removed from 451 reefs, over 830,000 hectares of habitat protected, and more than 160,000 hours of diving. Six boats each carry six to ten divers.

Funding follows. About 20 million Australian dollars per year are planned from 2022 to 2030, for roughly 140 employees including 14% Indigenous people, according to the same page. The program dashboard, updated July 17, 2026, provides details by season. In 2024-2025, teams killed 73,881 crown-of-thorns starfish over 11,710 hectares and 232 reefs. For 2025-2026, the counter shows 64,879 starfish over 13,210 hectares and 220 reefs. Fewer starfish over more area, the trend is encouraging, but one season alone proves nothing.

However, the northern front remains active.

The most active hotspot is located between Cairns and Lizard Island, and GBRMPA speaks of the fifth recorded epidemic cycle on the reef. One of its scientists, Dr. Williamson, expects this northern surge to intensify in the coming years. We will follow up.

Why does the crown-of-thorns weigh so heavily on the Great Barrier Reef?

Because it eats living coral and reproduces massively. According to GBRMPA, an adult consumes the equivalent of its size in coral every day or every two days, and a mature female releases at least 200 million eggs per year. It can approach one meter in size.

Thus, the agency ranks crown-of-thorns outbreaks among the three main causes of coral decline, alongside tropical cyclones and bleaching. Only the starfish can be managed locally. One point deserves correction in passing: the crown-of-thorns is a native species of the reef, as GBRMPA reminds us, and the problem comes from its population outbreaks. The giant triton, one of its predators, is the subject of a hope for natural regulation on the Great Barrier, with no published result figures to date.

A word about the name. You will often read Acanthaster planci, including in the old version of this article. In 2017, Gerhard Haszprunar and two colleagues advocated the name Acanthaster solaris for the Pacific population, genetically distinct from that of the northern Indian Ocean. The authors themselves acknowledge that a reference specimen still needs to be designated to fix this name. For you, it changes nothing while diving.

Reference	Value	Source and date
Maximum size	Nearly one meter in diameter	GBRMPA, 2026
Eggs per mature female	At least 200 million per year	GBRMPA, 2026
Coral consumed	Its size in coral every one to two days	GBRMPA, 2026
Dose of bile salts	10 ml, one injection at the base of an arm	Rivera-Posada et al., 2014
Dose of vinegar	25 ml, death in less than 48 hours	Boström-Einarsson and Rivera-Posada, 2016
Starfish removed since 2012	Nearly 1.4 million from 451 reefs	GBRMPA, March 2026

Vinegar or bovine bile: what do JCU studies say?

Both kill the starfish with a single injection. In 2014, a JCU team led by Jairo Rivera-Posada set the dose of bile salts at 10 ml, injected at the base of an arm with a 16-gauge needle. In 2016, Lisa Boström-Einarsson and the same researcher showed that 25 ml of household vinegar kills the animal in less than 48 hours.

The 2014 study, published in Ocean & Coastal Management, tested the bile solution in the laboratory and then at sea, on starfish measuring up to 42 cm. The authors noted no immediate effect on fish, corals, or other benthic invertebrates. This is the foundation of the current program.

But vinegar has its own advantages. In its September 2015 press release, JCU explained that it costs about half as much as bile extract and can be purchased without a permit at supermarkets. One detail is off though (and we prefer to point it out). The press release mentioned 20 ml, whereas the article published in Coral Reefs in 2016 uses 25 ml, with functional death in less than 24 hours. We rely on the publication. It was peer-reviewed.

On the Great Barrier Reef, divers in the program now use either solution, according to GBRMPA.

Is vinegar enough to stop an outbreak?

No, and no one in the program claims otherwise. Each starfish must be located and then injected by a diver, one by one. With six boats, teams focus their efforts on about 500 of the more than 3,000 reefs in the park, according to a Newsport article dated January 28, 2026.

However, the method remains inexpensive where applied. GBRMPA estimates the cost at about 175 Australian dollars per hectare protected, on a page from January 2026.

The agency mainly advocates early intervention. “The earlier we act, the more reef we protect,” summarizes its operations manager in March 2026. Teams therefore also monitor reefs that are still little affected. The goal is to act before starfish density rises. And the old version of this article described drones, DNA sensors, and citizen networks as routine tools. We found no dated source confirming this at the program scale. So we removed them.

In short, vinegar buys time on selected reefs, and that is already a lot when you know that an adult starfish can consume its size in coral in one or two days, on a reef that will take years to recover.

You encounter a crown-of-thorns while diving: what to do?

Do not touch it and do not inject it yourself. Its spines carry toxins. On the Great Barrier Reef, removal is handled by trained teams from the program, and your role stops at reporting to your guide or the dive center that takes you to the site.

But reporting is valuable if it is precise.

If the boat briefing mentions crown-of-thorns on the site, ask who to report what you see to. Note the location, approximate depth, time, and number of starfish. A photo taken from a distance, without contact, helps confirm the species. Maintain your buoyancy above the reef, as with any basic rule to never touch marine life. And if you want to distinguish the crown-of-thorns from another species before your dive, our fact sheet on starfish and their relatives provides visual cues. Also consider the rest. A poorly chosen sunscreen affects marine environments in another way.

The cost for you is just a minute during ascent, time to note four pieces of information underwater or on the deck. For the program, it is an additional data point on a reef that six boats cannot visit every week.

FAQ

Does vinegar kill other reef animals?

For bile salts, the 2014 JCU study found no immediate effect on nearby fish, corals, and invertebrates. For vinegar, no published long-term impact measurements on neighboring fauna have been found. Impossible to decide for now.

How many crown-of-thorns have been removed from the Great Barrier Reef?

Nearly 1.4 million from 451 reefs since 2012, according to GBRMPA as of March 26, 2026. In the 2025-2026 season, the program dashboard counts 64,879 starfish killed over 13,210 hectares.

Is the crown-of-thorns an invasive species in Australia?

No. GBRMPA describes it as a native species of the Great Barrier Reef. The problem comes from its population outbreaks, with the current surge being the fifth recorded on the reef.

Can a recreational diver inject a crown-of-thorns?

The rule depends on the country and area. On the Great Barrier Reef, removal is conducted by program teams. Without a clear local framework, you refrain and report what you see to your guide.

Sources

• Crown-of-thorns starfish (COTS) Control Program (Great Barrier Reef Marine Park Authority, 2026)
• Controlling outbreaks of the coral-eating crown-of-thorns starfish using a single injection of common household vinegar (James Cook University, Coral Reefs, 2016)