2016 SoE Marine Chapter - State and Trends - Crown-of-Thorns Starfish (COTS) outbreaks

The Marine chapter of the 2016 State of the Environment (SoE) report incorporates multiple expert templates developed from streams of marine data. This metadata record describes the Expert Assessment The state and trends of ecological processes – Crown-of-Thorns Starfish (COTS) outbreaks.The full Expert Assessment, including figures and tables (where provided), is attached to this record. Where available, the Data Stream(s) used to generate this Expert Assessment are accessible through the "On-line Resources" section of this record.

DESCRIPTION OF ECOLOGICAL PROCESS FOR EXPERT ASSESSMENT COTS (Acanthaster planci) are natural predators of coral and occur on all coral reefs in Australia’s marine domain. High fecundity means that when spawning coincides with favourable conditions, resulting recruitment can lead to outbreak densities of large starfish that can deplete local coral cover within 3-5 years. Populations then collapse through starvation and disease but not before they spawn abundant planktonic offspring, which may form secondary outbreaks on downstream reefs. There have been four synchronised eruptions of secondary outbreak in the highly connected, archipelagic Great Barrier Reef (GBR) since 1960. In the subsequent 15-20 years, multi-generational waves of secondary outbreaks have progressed southward through the central GBR. Average coral cover on GBR reefs fell by half over 27 years of monitoring to 2012; about 40% of the total decline was attributed to COTS. Outbreaks have also been recorded in all other parts of the starfish’s Australian range (Far northern GBR, Torres Strait, northwest WA), but their significance is uncertain since systematic monitoring was only recently implemented or is non-existent. DATA STREAM(S) USED IN EXPERT ASSESSMENT The assessment is based on data and analysis published in peer reviewed literature and unpublished reports. Details of specific data sets used to generate the assessment have not been provided.

2016 SOE ASSESSMENT SUMMARY [see attached Expert Assessment for full details] • 2016 • Assessment grade: Poor Assessment trend: Unclear Confidence grade: Adequate high quality evidence and high level of consensus Confidence trend: Adequate high quality evidence and high level of consensus Comparability: Grade and trends are somewhat comparable to the 2011 assessment • 2011 • Assessment grade: Good Assessment trend: Stable Confidence grade: Limited evidence or limited consensus Confidence trend: Adequate high quality evidence and high level of consensus

CHANGES SINCE 2011 SOE ASSESSMENT Since the 2011 assessment there has been widespread outbreaks of COTS detected across its range. There is a general lack of information with which to determine long term trends and so trends are regarded as unclear rather than stable.