Reef-World Launches Green Fins Crown-of-Thorns Sea Star Cleanup Guidelines

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The Reef-World Foundation – the international coordinator of the UN Environment Programme's Green Fins initiative – has launched new guidelines to help dive and snorkel operators assess when to conduct crown-of-thorns sea star (COTS) cleanups and how to do so in an environmentally friendly way.

Crown-of-thorns sea stars (Acanthaster planci) are common to reefs throughout the Asia-Pacific region, Australia and the Red Sea. They are predators of coral but prefer to feed on the polyps of faster-growing corals, thus allowing slower-growing corals to mature and ensure continuing diversity of the reef ecosystem.

The removal of the COTS' natural predators through several factors including overfishing and habitat destruction, plus warmer waters which encourage the rapid growth of COTS larvae, can lead to population outbreaks that are devastating to coral reefs. Removing them is essential to the preservation of the reef, but the sea stars are venomous, and improper handling can make the situation worse.

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The Green Fins guidelines provide some basic ecological information about COTS to help marine tourism operators learn more about the species; the role they play in a balanced ecosystem, why outbreaks occur, what signs indicate a COTS outbreak is happening and what steps need to be taken to protect the reef. The guidelines also include advice on how to organise COTS cleanups for operators who are dealing with a local outbreak.

Samantha Craven, Programmes Manager at Reef-World, said: 'Over the years, we’ve heard from Green Fins members who are facing COTS outbreaks and need support in dealing with the issue without inadvertently having a negative impact on coral reefs. That’s why we’ve created these Green Fins Crown-of-Thorns sea star cleanup guidelines, which summarise existing scientific guidance into one handy resource. The comprehensive resource can be used to ensure you and your team know when to act and are protecting marine habitats by following environmental best practice when dealing with an outbreak situation. We hope they’re useful to our network of Green Fins members and non-members alike.'

Gabriel Grimsditch, marine ecosystems expert at the UN Environment Programme, said: 'COTS are well known to divers as a threat to corals, but they are also a natural part of a reef system. Keeping fast-growing corals in check allows space for the high diversity we are used to seeing, and COTS cleanups are not always recommended. The Green Fins Crown-of-Thorns Sea Star Cleanup Guidelines will help marine tourism operators gauge when a clean-up is really needed and adapts information on conducting cleanups from COTS experts and reef management organisations specifically for the diving industry.'

The guidelines are available free of charge and can be downloaded from the Green Fins website.

For more information about Reef World and Green Fins, visit or, or follow the team on FacebookInstagram and Twitter. Dive and snorkel operators interested in signing up to Green Fins can find the membership application form at:


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