Limits to understanding and managing outbreaks of crown-of-thorns starfish (Acanthaster spp.)

Outbreaks of crown-of-thorns starfish (Acanthaster spp.) remain a major cause of coral mortality in the Indo-Pacific, contributing to widespread and accelerating degradation of coral reef environments. This review examines the evidence for and against the principal hypotheses put forward to explain spatial and temporal patterns of outbreaks and also explores whether it is possible or feasible to intervene and limit ongoing degradation caused by crown-of-thorns starfish. The inherent biological characteristics of Acanthaster spp., such as exceptional fecundity, early maturation, and extreme flexibility in resource use, clearly contribute to extreme fluctuations in their abundance. Of the many hypotheses put forward to explain the occurrence of outbreaks, none has universal or unequivocal support. Clearly, however, the high incidence and severity of outbreaks at many reef locations cannot be sustained because anthropogenic changes to marine environments either have caused fundamental shifts in the population dynamics of Acanthaster spp. or have undermined the capacity of reef ecosystems to withstand these periodic disturbances. Reducing the incidence or severity of outbreaks of Acanthaster spp. is critical for reversing widespread and protracted declines in coral cover throughout the Indo-Pacific. Improved efficiency of direct controls provides opportunities to limit the progression and spread of outbreaks if detected early, but effective management of Acanthaster spp. really depends on definitive knowledge and appropriate action to address the ultimate causes of outbreaks. There are considerable, but not insurmountable, challenges to addressing important and persistent knowledge gaps relating to the biology of Acanthaster spp. This research is fundamental to ensure the persistence of coral reef ecosystems, especially given other emerging threats associated with global climate change