Crown-of-Thorns starfish in the Whitsundays

The crown-of-thorns starfish is a native species to the Great Barrier Reef Marine Park. It is a predatory species that eats fast growing coral such as staghorn or plate, which are in abundance on the reef. In recent years, the Marine Park Authority have recorded a population increase in the crown-of-thorns, which is resulting in a potentially problematic imbalance on the reef.

The regular outbreak of crown-of-thorns starfish on the Great Barrier Reef has been ongoing as far as records can show. Core samples from the Great Barrier Reef show that the crown-of-thorns have always a part of the ecosystem. However, the recent population boost is resulting in mass losses of coral population that it feeds on, which is worrying scientists and researchers. 

When they do happen, outbreaks generally begin in northern waters and spread south with the prevailing currents, meaning they often hit the Whitsundays much later than the rest of the Great Barrier Reef.

With one female crown-of-thorns starfish producing up to 60 million eggs per year, and the starfish's ability to regenerate itself from just one severed limb and part of the central disc, the crown-of-thorns starfish is a diverse and effective species that can survive in a large variety of conditions. Growing to 80cm across in adulthood with 20 arms in total the crown-of-thorns is unmistakeable in appearance. It can reproduce in the millions upon a single reef, where they feed on the coral on an astronomical scale. They do this by turning their stomach inside out and digesting the living coral off its skeleton, leaving a bleached shell behind. When the crown-of-thorns occurs in such large numbers, like it currently is, it can lead to devastation and destruction of the reef.

While the Whitsunday Islands themselves remain largely unaffected, there have been recent outbreaks close by on several nearby sections of the Outer Reef, where large numbers of crown-of-thorns starfish are being monitored and culled to ensure they do not become overpopulated.

Although the crown-of-thorns starfish are sighted in the Whitsundays, currently they have little negative impact on the health and diversity of the reef. They are a vital member of the health of the reef when they maintain a good balance with the rest of the reef's residents, and so are a normal thing to see when snorkelling or scuba diving. And, while the danger of an outbreak is present, the crown-of-thorns starfish, like all species, still remains part of the delicate balance that gives us the spectacular environment of the Whitsundays.