Invasive starfish infestation cause for concern |17 December 2014

There is a need for effective, targeted and controlled management methods to be adopted in order to control or stop invasion by the crown of thorns invasive starfish which have appeared on our reefs, a survey has found.

The crown of thorns starfish (cots) is a coral predator. Outbreaks have occurred before in Seychelles, most recently in 1997 prior to the coral bleaching episode that killed much of the coral around Mahé and thus deprived the starfish of its food – so it died out again.

Earlier this year it reappeared – perhaps indicating that the ecological conditions on local reefs are not adequate to control the densities of the starfish by natural means.  

Swarms of starfish have appeared on the reefs, perhaps moving in from deeper water and – most alarmingly – they are spawning successfully.  At least three generations of starfish are now on the reefs and another spawning episode is expected anytime soon.

A long-term response is being developed by the government to deal with the outbreak and to monitor populations in the future to try to predict when outbreaks are likely to occur.  

To do this, however, there is a need to train people to monitor the populations on the reef, particularly the emergence of swarms of adults of spawning size, which needs to be removed, and failing that,  to monitor the presence of very small starfish before they grow to spawning size.
 
Unfortunately the young ones are quite difficult to spot – hence the need for training.

Staff of Seychelles National Parks Authority (SNPA), environment and nature conservation NGOs, dive companies and other stakeholders have followed training in how to survey and remove the cots. The training was funded by the government and the United Nations Development Programme – Global Environment Facility (GOS-UNDP-GEF) mainstreaming bio-security project.

The training was combined with a detailed survey of the starfish population on the reefs of north-west Mahé, a favourite area for snorkelling and diving and therefore an area where there could be severe economic (as well as ecological) repercussions if the reefs are heavily damaged by the cots invasion.

Dr Udo Engelhardt, an international cots expert who conducted the training made a short  presentation recently on the training undertaken, provided an assessment of the severity of the impact of the cots outbreak on the reefs and on the tourism industry, as well as indicated how the situation may be addressed.  

He noted that the present situation is a cause for concern and there is a need for a concerted eradication effort by all stakeholders.

“Everyone needs to work together, divers  for instance should report each time they come across cots and not just turn away as this provides further opportunity for cots to spread,” he said, adding that regular, routine surveys and consistent surveillance are key to eradicating the problem.

He noted that the most effective and safe control of cots is by injecting them with sodium bisulphate or bile salts as manual removal is too time consuming and risky.