What’s eating Crown of Thorns? How Tropical Water Quality Hub is answering questions on a coral-eating predator

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Research spanning multiple fields and institutions is filling knowledge gaps on the factors affecting outbreaks of the coral-eating Crown of Thorns Starfish (CoTS) on the Great Barrier Reef under a collaborative framework supported by the Tropical Water Quality Hub. Among other factors, the removal of natural predators of CoTS is currently being studied as a possible cause of outbreaks. PhD student Jennifer Wilmes, working on a Tropical Water Quality Hub project with Professor Morgan Pratchett at the ARC Centre of Excellence for Coral Reef Studies, examined bite injuries on 200 juvenile CoTS, comparing them across open and closed fishing zones, microhabitats (living coral vs dead coral) and size.

Ms Wilmes’ findings did not show much difference in bite injuries between juvenile CoTS taken from reefs protected from fishing and those from reefs being fished. This suggests that these bite injuries are unlikely to be caused by fish species protected in no-take zones. Initial findings from research led by Dr Frederieke Kroon at the Australian Institute of Marine Science under the same TWQ Hub project suggest that the starfish are being targeted by several coral reef fish species previously not considered. Examining fish poo for CoTS DNA, Dr Kroon’s study has identified additional fish species, including the Neon Damselfish (Pomacentrus coelestis) and Floral Maori Wrasse (Cheilinus chlorourus), as potential CoTS predators. Combined, these studies demonstrate that predation by a variety of coral reef fish species is likely an important factor in regulating CoTS numbers and abundance. A link to Ms Wilmes’s paper can be found on the Tropical Water Quality website.