The historical answers to the question of how to control the crown-of-thorns starfish are varied, both in method and degree of success.

The first control measures using chemicals were undertaken in 1936.

In 1957, physical removal and burial ashore managed to clear an impressive 220,000 crown-of-thorns starfish at the Miyako Islands in Japan in one go.

More recently, in 2018 on the Swains Reef on the southern Great Barrier Reef, large numbers of crown-of-thorns starfish were lethally injected after "catastrophic losses" of coral.

The Japanese territory of the Miyako Islands, shown off the east coast of Taiwan. Image credit: Getty Images/KeithBinns

Other culling programs have involved extracting the starfish from the water and injecting them with various compounds, or injecting them with air and collecting them when they floated to the surface.

These methods are extremely laborious with varying rates of removal, and some of the compounds used for injecting were found to have a detrimental impact on the environment.

“Many millions of dollars have been spent over many years on a variety of ways to capture crown-of-thorns starfish."

All in all there have been more than 120 crown-of-thorns mitigation programs, which have removed close to 20 million starfish.

This effort has helped to protect some specific reefs, yet the regional-scale problem has not diminished.

The Great Barrier Reef extends for 2300km along Australia's north-east coastline. Image credit: Getty Images/Rainer Lesniewski

“For an already struggling Great Barrier Reef and, indeed, any reefs across the Indo-Pacific region, crown-of-thorns starfish pose an enormous threat due to their reproductive ability,” Bernard Degnan says.

“They feast on the coral with mouths 10 times larger than other starfish and leave it bleached white and vulnerable to destruction from a range of forces including heavy storms.

“Many millions of dollars have been spent over many years on a variety of ways to capture crown-of-thorns starfish, whether it be via diver collection, injections or robotics.”