Condiment kills crown-of-thorns starfish

A new weapon in the battle against the coral-eating, crown-of-thorns starfish is about to be unleashed — and it’s a condiment.

Field trials by the Great Barrier Reef Marine Park Authority and James Cook University at Arlington Reef, off Cairns, confirmed a dash of household vinegar is lethal to the voracious starfish, when administered via injection.

The findings are welcome news for more than 30 individuals and business operators — mainly working in the tourism industry — who are authorised to cull starfish under the Authority’s control program, in order to safeguard the Reef and their livelihoods.

“The relentless predator has been responsible for a large percentage of coral deaths over the past 50 years – but it has an Achilles’ heel,” Marine Park Authority Crown-of-thorns starfish Project Manager Dr Mary Bonin said.

“Starfish are simple animals that can’t regulate their own internal pH levels.

“If they’re injected with white vinegar, which contains acetic acid, they die within 48 hours and begin to disintegrate.”

The vinegar-laced starfish pose no threat to other marine species, according to a rigorous environmental impact assessment of the trial sites.

In fact, fish species known to dine on dying crown-of-thorns starfish were found to equally relish “pickled” starfish.

“We have videos showing these species actively feeding on dying crown-of-thorns starfish that have been injected with vinegar,” Dr Bonin said.

“And surveys undertaken before and after the field trial indicates there has been no impact on fish numbers.”

Readily available on supermarket shelves for around $0.60 per litre, vinegar is both less expensive and more accessible than bile salts, the most commonly used compound to cull the starfish at present.

A single, deadly 20 ml-dose of household vinegar, injected at the base of a starfish arm with a modified drench gun, costs around one cent.

“Access to bile salts can be difficult in developing countries and also challenging for business operators and the general public in other countries, due to quarantine restrictions and specialised import permit requirements,” Dr Bonin said.

“The chemical can be expensive as well and has a limited five-day shelf life once mixed in solution, which can further increase costs for small-scale control programs, because unused solution may have to be discarded.”

Association of Marine Park Tourism Operators Crown-of-thorns starfish Project Manager Steve Moon said vinegar promised to be a valuable and cost-effective tool in Australia and overseas.

“Any new innovation in the fight to suppress crown-of-thorns populations is always welcome,” he said.

“Vinegar as an alternate means of control will greatly enhance the ability for tourism operators, isolated communities and developing island nations to contribute more effectively to crown-of-thorns control.”

The Marine Park Authority recently issued new guidelines for control permit holders, detailing how to use the vinegar solution.

“It’s a recipe that hopefully signals a new stage in the battle to turn the tide on COTS infestations threatening the Reef,” Dr Bonin said.

For information on how to obtain a permit to conduct crown-of-thorns starfish control is available on our website.

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