Divers kill crown-of-thorns starfish with vinegar

Crown of thorns starfish, COTS

Scientists in Australia have discovered that vinegar kills Crown-of-Thorns Starfish just as effectively as the current drug, which can be expensive and difficult to source.

Outbreaks of the venomous Crown-of-Thorns Starfish (Acanthaster planci) pose one of the most significant threats to the Great Barrier Reef.

Researcher Lisa Boström-Einarsson said vinegar had been tried unsuccessfully before, but James Cook University scientists refined the process which resulted in a 100% kill rate. The animals are breeding at epidemic levels.

Ms Boström-Einarsson said the findings were exciting. “Currently divers use 10 or 12 ml of ox-bile to kill each Crown-of-Thorns Starfish. It’s expensive, requires permits and has to be mixed to the right concentration. We used 20 ml of vinegar, which is half the price and can be bought off the shelf at any local supermarket.”

The starfish all died within 48 hours of being injected.

“It has been estimated there are between 4 and 12 million of the starfish on the Great Barrier Reef alone and each female produce around 65 million eggs in a single breeding season. They managed to kill around 350 000 last year with two full-time boat crews. While it would take an insane effort to cull them all that way, we know that sustained efforts can save individual reefs,” Ms Boström-Einarsson commented.

She said other researchers were working on population-level controls of the animal, but killing the starfish one-by-one was the only method available at the moment.

Sea trials of the vinegar method will begin by the end of the year.

Starfish-Killing Robots might also be Unleashed

At the Queensland University of Technology they are investigating an alternative method for killing the starfish – robots. Called a COTSbot, it is designed to search the reef for up to eight hours at a time, delivering more than 200 lethal shots.

Its creator, Dr Matthew Dunbabin, says the COTSbot is equipped with stereoscopic cameras to give it depth perception, five thrusters to maintain stability, GPS and pitch-and-roll sensors and a unique pneumatic injection arm to deliver a fatal dose of bile salts.

If the robot is unsure that something is actually a crown-of-thorns starfish, it takes a photo of the object to be later verified by a person, and that human feedback is incorporated into the robot’s memory bank.

The COTSbot is planned to be working the reef autonomously in December.