A Prickly Situation

What marine creature can have up to 21 arms, hundreds of venomous spines, a taste for coral, and the ability to appear in plague-like numbers?
If you guessed the Crown-of-thorns starfish, you’d be right!
Often referred to as COTS, Crown-of-thorns starfish are native to the Great Barrier Reef and are not an introduced species.
According to the Australian Institute of Marine Science, genetic studies have shown that there are at least four species of COTS. The species found on the Great Barrier Reef is currently referred to as Acanthaster cf. Solaris.
These large marine invertebrates feed on coral as adults, playing a significant role in the reef ecosystem. However, when their numbers surge, they can cause widespread damage.
COTS outbreaks are a major cause of reef-building coral loss on the Great Barrier Reef, with each starfish capable of consuming up to 10m² of hard coral per year. In addition, they have an incredibly fast reproductive rate, with a single female able to release millions of eggs annually.
Master Reef Guides in the Whitsundays often assist in controlling excess numbers at local tourism sites, while the COTS Control Program works throughout the Great Barrier Reef World Heritage Area to monitor and manage outbreaks.
The COTS Control Program uses a combination of data and modelling to prioritise reefs based on their ecological and economic value to the wider reef. So far, in the 2023–2024 period, the program has targeted 192 priority reefs, protected 11,640 hectares of reef habitat through targeted culling, and removed 50,227 Crown-of-thorns starfish.
The Crown-of-thorns starfish isn’t just a thorn in the reef’s side, it’s a royal pain for the coral. For updates on the work being done to manage them, head to the Great Barrier Reef Marine Park Authority website:
Www2.gbrmpa.gov.au
Fast Fact: COTS have eyes in their arms.