Not all starfish get a gold star when it comes to reef health. Despite being native to the Great Barrier Reef, large outbreaks of the coral-crunching crown-of-thorns starfish pose a significant threat to its survival.

Australian Institute of Marine Science research shows that over the past 30 years, coral cover on their surveyed reefs declined by about 50 per cent. Crown-of-thorns starfish were responsible for almost half of this decline. In fact, without these predatory starfish devouring reef corals, researchers estimate that there would have actually been a net increase in average coral cover.

But it’s not all bad news – there is a slice of silver lining under that spiky crown.

The Great Barrier Reef Marine Park Authority says the coral-eating starfish plays an important role on healthy coral reefs. Because it tends to feed on the fastest growing corals such as staghorns and plate corals, this allows slower growing coral species to form colonies. This helps increase coral diversity on reef ecosystems.

Taking AIM at the crown-of-thorns starfish – with giant killer snails of course

A new federal government funded project at the Australian Institute of Marine Science (AIMS) is taking aim at the crown-of-thorns starfish with a breeding program of the starfish’s natural predator, the giant triton sea snail.

This project builds on the success of previous AIMS research which found that crown-of-thorns starfish will actively try to avoid an area where triton sea snails are present.

And when you see what happens when this spiky starfish meets its nemesis, it’s not hard to see why they’d want to steer clear!

Not even the starfish’s sharp spines complete with toxic coating can deter these giant snails from making a meal of them.

Find out more about the AIMS giant triton breeding program

Tourism weighs in to help

The tourism industry is also in on the fight to control outbreaks of the deadly crown-of-thorns starfish (COTS).

The Australian Marine Park Tourism Operators Association (AMPTO) run a dedicated COTS eradication program that includes deploying boats to danger spots with the support of the Great Barrier Reef Marine Park Authority.

The program trains and employs teams of COTS killers who are skilled in spotting and destroying outbreaks of the coral munching starfish using an injection of bile salts.

With two boats and a smaller surveillance vessel at the ready through federal government funding, the AMPTO team is continuing the fight to keep this potentially devastating coral predator under control.

AMPTO estimates that their current program, which started in 2012, has removed more than 570,000 – that’s over half a million – crown-of-thorns starfish from the Great Barrier Reef.

And while that number is staggering enough, here are some even bigger numbers.

• 60 million – the number of eggs a small crown-of-thorns starfish can produce in one spawning (breeding) season
• 1 billion – the number of eggs a large crown-of-thorns starfish can produce in one spawning (breeding) season
• 1.3 metres – the diameter of some of the AMPTO team reports catching – that’s about the height of a four drawer filing cabinet, ie massive!

AMPTO also helps train tourism operators who are out on the Reef every day to keep watch for and report sightings of the predators.

Anyone who visits the Reef can help too. Through the Great Barrier Reef Marine Park Authority’s Eye on the Reef program, you can report sightings of the deadly starfish. This assists the marine park managers with monitoring and identifying any trouble spots where further investigation and action may be needed.

For more info about crown-of-thorns starfish, head to the Great Barrier Reef Marine Park Authority website.