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MOVEMENT
25. Do crown-of-thorns starfish move between reefs? Often, during the early stages of an outbreak large numbers of starfish (sometimes in long lines: see Fig. 4) are observed moving from deeper water up the slopes of reefs. This has given rise to the belief that outbreaks may develop as a result of the movement of large numbers of adult starfish across the sandy bottom between neighbouring reefs. At present there are no data to indicate that outbreaks arise in this manner. The sudden appearance of adult starfish in deeper water could occur if the larvae had settled at the bases of the reefs (ie. 20-30 m in depth) some 2 years earlier. These areas are rarely surveyed for reasons of logistics. In theory, healthy crown-of-thorns starfish have the ability to move between nearby reefs (ie. about I kilometre apart) since they are capable of going without food for relatively long periods of time (see 20) and can move quite quickly (see 24). In practice however, this may not occur since the starfish may not be able to maintain such high rates of movement consistently over long periods. Furthermore, it may not be possible for starfish to maintain a constant high rate of movement over prolonged periods without obtaining some nutrition. Information concerning maximum lengths of starvation comes from captive animals and not ones continually moving. Starfish have been observed in deeper water (ie. 40-50 m) between reefs using remotely operated television cameras. Also, crown-of-thorns starfish have been reported moving back into deeper water at the end of outbreaks. Unfortunately, this does not provide direct evidence of their movement between reefs. In order to prove this, it is necessary to demonstrate that an individual starfish recorded on one reef was found some time later on another nearby reef. This would require the development of a suitable tagging system (see 30).
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