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OUTBREAKS
15. Where do all the starfish go at the end of an outbreak? It would seem likely that the eventual fate of crown-of-thorns starfish after an outbreak would be known, particularly since these populations may comprise hundreds of thousands of individuals (see 10). Unfortunately, there is very little information about this question mainly because the decline of crown-of-thorns starfish populations can be very rapid (see 14). Despite this some scientists have suggested that the starfish move in large numbers to nearby, undisturbed reefs once the majority of corals have been eaten on the previous reef (see 25). Others have argued that the starfish become stressed due to a lack of food and contract a disease which causes the majority of them to die quickly (see 32). There is very little evidence to support any of these hypotheses. Whilst starfish have been observed moving in from deeper water at the beginning of outbreaks there are no observations of armies of starfish moving doggedly in a wave between neighbouring reefs. Indeed, if this is a common occurrence then it is surprising that few starfish have been found between reefs. The finding of small numbers of starfish from time to time in such areas (eg. in nets of fishing trawlers or recorded by underwater video cameras) does not provide evidence of movement from reef to reef, rather only evidence of their occurrence between reefs. Furthermore, there are no reports of masses of crown-of-thorns starfish dying on reefs (there are only a few reports of individual starfish dying in the field), although it is known that they do suffer from a disease which may be important in causing their death (see 32). This is somewhat perplexing given that it takes about 4-6 days for a crown-of-thorns starfish to fully decompose in the field. One would expect to see some evidence of mass mortality of starfish on reefs particularly when the outbreaks involve many thousands of individuals and decline within a relatively short space of time (ie. 2-3 months). This type of event has been reported for other coral reef echinoderms.
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