Large numbers of juvenile crown-of-thorns starfish have been observed during recent surveys of reefs offshore from Cairns and Port Douglas.

High densities of small juvenile starfish, less than 13 centimeters in diameter, were recorded at 13 of the 21 reefs surveyed, suggesting the 1997-8 recruitment in the region has been widespread. The high density populations (more than 50 individual starfish per reef sampled) were observed by CRC researchers during surveys between October 1998 and April 1999.

Survey leader Udo Engelhardt says: "While it is difficult to predict the ultimate fate of the current juvenile populations, there is clearly a strong potential for severe outbreaks to develop on these reefs over the next 12 to 18 months."

Researchers concede it is difficult to accurately predict the likely population trends at this stage. Given the high numbers of juveniles on the same reefs that experienced outbreaks during the last major cycle, there is a possibility many starfish could die out before reaching adulthood. The current juvenile population may actually delay the coral recovery phase of these reefs as they grow and compete for food. However, past records show that total juvenile COTS counts as low as 25 individuals per reef have turned out to be reliable indicators of future outbreaks.

Researchers are currently reporting results of the 1998-99 survey season to key user and interest groups and aim to make the next summer season reports available within three week of individual survey trips. The early warning system is proving invaluable to better understand the likely future situation.

Whatever the trend, CRC researchers, marine tourism operators and managers from the Great Barrier Reef Marine Park Authority and Queensland Parks and Wildlife Service will continue to monitor starfish populations and report results to government, industry and community groups at the earliest opportunity. One initiative, currently being negotiated by several Caims-based tourism operators, is to expand site eradication programs, where trained divers inject and kill COTS with sodium bisulfate on a regular basis. For further information contact Udo Engelhardt at Reef Watch Australia in Townsville. Mailto: Reefwatch@ozemail.com.au