A team of marine biologists, conservationists and environmentalists affiliated with multiple institutions in Australia has found that controlled culling of starfish can revitalize or promote regrowth of sections of the Great Barrier Reef.
In their paper published in the open-access journal PLOS ONE, the group describes how they conducted culling operations on several parts of the Great Barrier Reef and then studied the results to learn about how such activity can benefit coral reefs in general.
Prior research has shown that coral reefs around the world are in trouble, due mostly to human activities. Warming water and an increase in acidification due to the infusion of carbon dioxide from the atmosphere are making life difficult for coral, resulting in reductions in reef size.
Another factor in their reduction is the growing population of starfish, such as the crown-of-thorns. Just one of them, a meter in diameter, can eat 10 square meters of coral every year. In this new effort, the research team focused on helping coral survive in the Great Barrier Reef by reducing the number of starfish in the area.
To reduce the number of starfish, the research team engaged in a culling effort, which meant diving down into the sea, identifying individual crown-of-thorns starfish, and injecting them with vinegar or ox bile, which killed them and also prevented them from releasing larvae—over the years 2012 to 2022. They focused the culling effort on 500 of the park’s 3,000 reefs.
In monitoring the areas where culling was conducted, the researchers found that coral recovered with a 44% increase in reef coverage. They also found that in nearby parts of the reef where no culling had occurred, loss of coral continued unabated.
Additionally, the research team found that culling the starfish in specifically targeted areas dramatically reduced the spread of larvae, preventing outbreaks in other reefs.
The researchers describe their effort as similar to pest management. As human activities, such as the release of fertilizers into rivers and streams which make their way to the sea have allowed starfish populations to explode, the need has arisen to cull them.
The team suggests their test program has shown that culling of starfish can be an effective tool in helping to save the Great Barrier Reef—and other reefs around the world.