30 Years of Research on Crown-of-thorns Starfish (1986-2016): Scientific Advances and Emerging Opportunities

Abstract

Abstract:Research on the coral-eating crown-of-thorns starfish (CoTS) has waxed and waned over the last few decades, mostly in accordance with the occurrence of population outbreaks at key locations, such as Australia's Great Barrier Reef. This review considers advances in our understanding of the biology and ecology of CoTS based on the latest resurgence of research interest, which culminated in this current special issue on the Biology, Ecology and Management of Crown-of-Thorns Starfish. More specifically, this review considers progress against 41 specific research questions posed in the seminal review by P. Moran 30 years ago, as well as exploring new directions for CoTS research. Despite the plethora of research on CoTS (> 1,200 research articles), there are persistent knowledge gaps that constrain effective management of outbreaks. Although directly addressing some of these questions will be extremely difficult, there have been considerable advances in understanding the biology of CoTS, if not the proximal and ultimate cause(s) of outbreaks. Moving forward, researchers need to embrace new technologies and opportunities to advance understanding of CoTS biology and behaviour, with focus given to key questions that will improve effectiveness of management to reduce the frequency and likelihood of future outbreaks, if not preventing them altogether.Keywords: Acanthaster; coral reefs, disturbance; management; population outbreaks; research priorities Peer-reviewed version available at Diversity 2017, 9, 41; doi:10.3390/d90400412 of 50 BackgroundCrown-of-thorns starfish (CoTS; Acanthaster spp., excluding A. brevispinus) are renowned for their capacity to devastate coral reef ecosystems . This is primarily because local densities of CoTS can increase from normally very low densities (<1 starfish.ha -1 ) to extremely high densities (>1,000 starfish.ha -1 ) during periodic population outbreaks (e.g. Chesher 1969). Moreover, CoTS are one of the largest and most efficient predators on scleractinian corals (Birkeland 1989). Whereas most other individual coral-feeding organisms (e.g., Chaetodon butterflyfishes, and Drupella snails) cause only localised injuries or tissue-loss (Cole et al. 2008;Rotjan and Lewis 2008), adult CoTS can kill entire corals, including relatively large colonies. High densities of CoTS will therefore, cause rapid and extensive coral depletion. In French Polynesia, for example, high densities of CoTS caused systematic coral loss around the entire circumference of the island of Moorea, killing >96% of coral between 2005(Kayal et al. 2012). More broadly, outbreaks of Acanthaster spp. are a major contributor to sustained declines in coral cover and degradation of coral reefs at many locations throughout the Indo west-Pacific (Osborne et al. 2011;Trapon et al. 2011;De'ath et al. 2012).While there has been considerable research, and a larger number of scientific articles (>940) focused on Acanthaster spp., extending back to the 1960s (Goreau 1964;Pearson and Endean 1969), research interest (and fundin...