DECIDING WHEN A CLEAN-UP IS NEEDED
areas of reef may be killed before a clean-up operation begins, and further increases the danger to neighboring areas, which may become infected with their spawn. Quick action is
essential. A few months’ delay may mean the difference between success and failure.
Why should we sometimes not clean up COTs, even if there is an outbreak?
Tampering with a complex ecosystem such as coral reefs may initiate a series of unknown and potentially undesirable outcomes.Two often-cited reasons to leave COTs
populations alone, even if they are at outbreak level, are: 1. Outbreaks of COTs may actually help maintain the species diversity of corals.
2. If too many COTs are removed, the ecosystem may be thrown out of balance. The ecological hole created by the COTs removal may decrease competition for
food and result in the persistence of a few highly fecund adult COTs. As a result, the number of COTs larvae may increase and with a constant survival rate the
population could return to outbreak levels or worse Birkeland and Lucas, 1990. In each particular area, we must decide first whether a clean-up is likely to achieve
the goal of saving the coral reef, and then whether saving the reef in question is justified. An example of a COTs clean-up program that did not meet its goal of saving the
reef occurred in Japan. After a COTs cleanup, COTs numbers returned to the outbreak levels and in some places increased. Some researchers suspect that the clean-ups
responded too late to the crisis. It is unclear whether too many or too few COTs were removed, or whether other factors resulted in continuing outbreaks. Whatever the
explanation, the COTs populations remained at outbreak levels and destroyed the reefs of the Ryuku Islands Yamaguchi, 1987.
18 | Guide for Crown-of-Thorns Clean-Ups
3
SELECTING COTS CONTROL OPTIONS
In Indonesia, the recommended option for most small-scale community-based clean- up efforts less than 5,000 COTs in the area to be removed is hand-removal and burial
ashore. Other control options used elsewhere in the world for small areas include injec- tion of poison, use of underwater fences or cutting up COTs.