Hungry little crabs may help control coral-eating starfish numbers

A study published in Proceedings of the National Academy of Science of the United States of America (PNAS) Journal suggests that small, hidden decapod crabs may play a crucial role in controlling crown-of-thorns starfish (COTS) populations. COTS outbreaks can devastate coral reefs, but their population cycles remain debated. Researchers, led by Dr. Sven Uthicke, used eDNA analysis to detect COTS DNA in the guts of seven decapod species across 1,000 km of the Great Barrier Reef. They found fewer crabs in areas prone to COTS outbreaks, and their predation rates on juvenile starfish were significantly lower in these regions. This highlights the previously unrecognized role of decapod crabs in reef ecosystems.

Dr. Uthicke and his team found that hidden decapod crabs consume juvenile crown-of-thorns starfish (COTS) in their nurseries, preventing them from reaching their coral-feeding stage. Since crabs can eat up to 20 juveniles per day—compared to fish or tritons that consume one adult every few days—they are highly effective at reducing COTS populations. The study suggests that these crabs may influence COTS outbreak patterns and could play a role in reef conservation and management strategies.

Dr. Uthicke emphasized the need to understand the factors controlling crab populations to leverage their role in managing COTS outbreaks. The study, led by Dr. Kennedy Wolfe, involved researchers from multiple institutions, including The University of Queensland, CSIRO, AIMS, and James Cook University. It was funded by the Winnifred Violet Scott Trust and the COTS Control Innovation Program, supported by the Australian Government’s Reef Trust and the Great Barrier Reef Foundation. To learn more; head to the Australian Institute of Marine Science’s article https://www.aims.gov.au/information-centre/news-and-stories/hungry-little-crabs-may-help-control-coral-eating-starfish-numbers