Crown-of-thorns Starfish - Population Control

Population Control

Population numbers for the crown-of-thorns have been increasing since the 1970s. However, historic records distribution patterns and numbers are hard to come by, as SCUBA technology, necessary to conduct population censuses, had only been developed in the previous few decades.

To prevent overpopulation of crown-of-thorns causing widespread destruction to coral reef habitats, humans have implemented a variety of control measures. Injecting sodium bisulphate into the starfish is the most efficient measure in practice. Sodium bisulphate is deadly to crown-of-thorns, but it does not harm the surrounding reef and oceanic ecosystems. To control areas of high infestations, teams of divers have had kill rates of up to 120 per hour per diver. The practice of dismembering them was shown to have a kill rate of 12 per hour per diver and the diver performing this test was spiked 3 times. Therefore, it is for this reason and not rumors that they might be able to regenerate that dismembering is not recommended.

An even more labor intensive route, but less risky to the diver, is to bury them under rocks or debris. This route is only suitable for areas with low infestation and if materials are available to perform the procedure without damaging corals. In an attempt to save the Great Barrier Reef, the World Wildlife Fund said Australia must reduce fertilizer runoff as a first step to controlling the crown-of-thorns starfish. According to the study, the starfish in its larval stage feeds on plankton, populations of which surge when fertilizer runoff floods the coastal ocean waters with nutrients. So, plentiful plankton can lead to swarms of hungry starfish.