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Tuesday
Aug222017

What To Do With Crown Of Thorns Starfish  Outbreak?

Outbreaks of coral predators, specifically the Crown of Thorns (CoTs) starfish (Acanthaster planci) represent a serious cause for concern for Beqa’s reefs as these invertebrates are the dominant killer of Indo-Pacific reefs over any other disturbance events e.g. cyclones. Worryingly, attempts to control these outbreaks in other areas such as the Great Barrier Reef (GBR) have failed to mitigate against their devastating effect and they have been implicated with having a greater impact than the combined effects of coral bleaching and disease. The visual impact of these sudden population increases is clear, with living coral cover reduced to only a few % and dramatic decreases in coral reef productivity and biodiversity. The Frontier Fiji Marine (FJM) team have noticed higher than expected populations since relocating here in 2013 across core survey sites, which has been echoed by Beqa’s communities who have noticed sharp increases.

Currently, many of the sites are classified as having “non-outbreaking populations”, however CoTs feed selectively, and influence coral community structures by consuming more of their favourite food corals. For these reasons ensuring that their populations are monitored and controlled is a key aim for FJM here on Beqa. FJM will monitor the populations across Beqa as part of an important Pacific-wide initiative called “OREAnet”, which wants to map populations across the region using data submitted by local community members and organisations that dive frequently.

During removal exercises CoTs are recorded and culled using SCUBA and surface snorkel techniques during a set time period and then specimens will be weighed and measured on shore by RAs, staff and community members. By recording weight and diameter we can improve our understanding of Beqa’s reefs and the age of specimens that we collect, this can give us an understanding of whether there are a number of different age classes on the reefs. 

In terms of equipment FJM is going basic, as seen in the photos, using local ingredients and cheap tools that are easy to use which means that community members can carry out extractions independently. This means that communities can take care of their reefs, which they rely on for food and income, independently.

We also trailed some new “Mr Beefy” kitchen tongs for this extraction, these allow us to detach the CoTs from the reef without piercing them or excessively manipulating them.

This is important as they can release up to 60 million eggs when stressed and are capable of regeneration if sections are accidentally “cut-off”. Initial results through surveys conducted on our very own “House Reef” have shown higher than expected populations and that the individuals represent a number of different age classes from 2-3 years. However, all specimens found were adults over 2 years, which are often hard to find during the day as they hide under crevices. The kitchen tongs came in very useful for this section and allowed staff and volunteers to remove the specimens without damaging any coral.

By Claire Collins - Fiji Marine Research Officer

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