outbreaks

Controlling A. planci outbreaks :

Labor-intensive though it is, there have even been projects that involved injecting the offending starfish with a variety of poisons, such as 5% formalin solution (from formaldehyde, a gas, in water) copper sulfate (CuSO ₄), sodium hypochlorite (NaClO), ammonia (NH ₃), ammonium hydroxide (NH 4OH), compressed air, and acetic acid (CH ₃COOH). Currently, the most environmental tolerable control method of this kind is diluted sodium-bisulfate (NaHSO ₄·H 2O). Whatever solution is used, it is important to inject it into several areas of the starfish in order to make sure that it does not reject a damaged arm and regenerate it. Although this method is effective, it is too expensive and time-consuming to be widely used. The most cost-effective method known at present is to enlist the help of amateur divers and remove the starfish by hand. An even cheaper option is to keep the crown-of-thorns (COT) out of an area by installing a wide-meshed fence. At the peak of the last A.planci outbreak, up to 15000 individuals were caught in one single day. Approximately 15 million starfish have been killed in control programs throughout the last 15 years in the Indo-Pacific region. By far the largest of these programs have been undertaken in the Ryukyu Islands, Japan, where almost 13 million starfish have been removed from the reefs in that region. Despite these intensive efforts (costing approximately $3 million) the control program in Japan is regarded to have been unsuccessful in either eradicating the starfish or preventing further coral mortality Poisoning or removal by hand are localized and temporary measures. They tend to be used only in popular tourist areas and provide cosmetic, short-term solution, that prevent further reef damage only until the next outbreak. With or without such action, most of the stars disappear, and if the time between outbreaks is long enough, and sea-surface temperatures do not exceed the thermal tolerance threshold, new corals may settle, thrive and replace those lost. Natural predators are also important methods of control as suggested by the following poster. However, these agents of control are ineffective under plague conditions.