18. Are crown-of-thorns starfish eaten by other animals?

A number of animals have been observed to attack and eat crown-of-thorns starfish. These records of predation are not limited solely to adults but also eggs, larvae and juveniles. The predators most commonly observed to feed on crown-of-thorns starfish are: the giant triton shell (Charonia tritonis) (see Fig. 9), a puffer fish (Arothron hispidus), two species of trigger fish (Balistoides viridescens, Pseudobalistes flavimarginatus), a shrimp (Hymenocera picta) and a worm (Pherecardia striata). Each has been recorded to feed on juveniles and small adults.

Figure 9 A giant triton, Charonia tritonis, feeding on a crown-of-thorns starfish.

At present there is no evidence to indicate that these or any other predators are capable of limiting the population density of crown-of-thorns starfish. Consequently, it is not known whether changes in the level of predation are responsible for causing outbreaks of this starfish (see 13). Whilst predation has been observed mostly on adults it is likely that it is also responsible for high mortality amongst the early life history stages when the starfish is most vulnerable (see 27). Unfortunately research into this particular aspect in the field is fraught with technical and logistic problems (eg. how does one go about finding these minute individuals when the distances involved are so vast and there are so many hiding places on a reef?).

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