title: Assessing Different Causes of Crown-of-Thorns Starfish Outbreaks and Appropriate Responses for Management on the Great Barrier Reef.
abstract: The crown-of-thorns starfish Acanthaster planci (COTS) has contributed greatly to declines in coral cover on Australia's Great Barrier Reef, and remains one of the major acute disturbances on Indo-Pacific coral reefs. Despite uncertainty about the underlying causes of outbreaks and the management responses that might address them, few studies have critically and directly compared competing hypotheses. This study uses qualitative modelling to compare hypotheses relating to outbreak initiation, explicitly considering the potential role of positive feedbacks, elevated nutrients, and removal of starfish predators by fishing. When nutrients and fishing are considered in isolation, the models indicate that a range of alternative hypotheses are capable of explaining outbreak initiation with similar levels of certainty. The models also suggest that outbreaks may be caused by multiple factors operating simultaneously, rather than by single proximal causes. As the complexity and realism of the models increased, the certainty of outcomes decreased, but key areas that require further research to improve the structure of the models were identified. Nutrient additions were likely to result in outbreaks only when COTS larvae alone benefitted from nutrients. Similarly, the effects of fishing on the decline of corals depended on the complexity of interactions among several categories of fishes. Our work suggests that management approaches which seek to be robust to model structure uncertainty should allow for multiple potential causes of outbreaks. Monitoring programs can provide tests of alternative potential causes of outbreaks if they specifically monitor all key taxa at reefs that are exposed to appropriate combinations of potential causal factors.
authors.affiliation: CSIRO Oceans and Atmosphere, Brisbane, Qld, Australia.|School of Plant Biology, University of Western Australia, Crawley, WA, Australia.
authors.forename: Russell C
authors.initials: RC
authors.lastname: Babcock
authors.affiliation: CSIRO Computational Informatics, Castray Esplanade, Hobart, TAS, Australia.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Dambacher
authors.affiliation: CSIRO Oceans and Atmosphere, Brisbane, Qld, Australia.
authors.forename: Elisabetta B
authors.initials: EB
authors.lastname: Morello
authors.affiliation: CSIRO Oceans and Atmosphere, Brisbane, Qld, Australia.
authors.forename: Éva E
authors.initials: ÉE
authors.lastname: Plagányi
authors.affiliation: CSIRO Computational Informatics, Castray Esplanade, Hobart, TAS, Australia.
authors.forename: Keith R
authors.initials: KR
authors.lastname: Hayes
authors.affiliation: Australian Institute of Marine Science, PMB 3, Townsville MC, Qld, Australia.
authors.forename: Hugh P A
authors.initials: HP
authors.lastname: Sweatman
authors.affiliation: ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD, Australia.
authors.forename: Morgan S
authors.initials: MS
authors.lastname: Pratchett
mesh_terms: D000818:Animals; D037421:Anthozoa; D057894:Coral Reefs; D020387:Food Chain; D011155:Population Control; D011158:Population Growth; D011235:Predatory Behavior; D013215:Starfish / Q000254:growth & development*