Eliminating invasive reef species – COTSbot and RangerBot

Eliminating invasive reef species

The COTSbot and RangerBot Autonomous Underwater Vehicle (AUV) projects have been focused on developing robotic systems to help reef managers and other community groups upscale underwater monitoring of the Great Barrier Reef and control of marine pests such as the crown-of-thorns starfish (COTS). The research emphasis has been on development of advanced real-time image processing techniques and underwater robotic platforms to detect, count and map the distribution of a range of marine pests. These systems are now being extended to more general coral reef monitoring and management activities by further exploiting robotic vision.


The COTSbot (Crown-Of-Thorns Starfish robot) is a revolutionary advancement in robotic environmental monitoring and management, specifically to increase the efficiency of Crown-Of-Thorns Starfish (COTS) eradication. Integrating state-of-the-art robotic vision and classification algorithms with experience in, and technologies for, shallow coastal water robotic monitoring, COTSbot also provides a flexible tool that empowers a range of stakeholders to scale current eradication programs and protection of reefs such as the Great Barrier Reef. This class of robot is designed to operate without a tether and execute missions with minimal human interaction once deployed. The key features of COTSbot include real-time and on-board automated image-based detection of COTS, autonomous injection of bile salts into detected COTS, and autonomous navigation within shallow coral reefs. COTSbot is 1.35 m long,weights approximately 30 kg with a maximum depth rating of 100 m.

The RangerBot AUV

The RangerBot AUV is a novel completely vision-based robotic tool that has been developed to provide coral reef managers, researchers and community groups extra ‘hands and eyes’ in the water to help monitor and manage various threats on the Great Barrier Reef. This includes monitoring reef health indicators like coral bleaching and water quality, mapping and inspection, and the monitoring and control of pests like the Crown-Of-Thorns Starfish (COTS). The RangerBot AUV significantly extends the capabilities of its predecessor, the COTSbot AUV, and exploits real-time on-board vision for navigation, obstacle detection and management tasks (e.g. COTS detection and injection). The RangerBot has been developed for single person deployment and operation from any size vessel or shoreline with an intuitive tablet-based interface created using feedback from key stakeholders. This project is in collaboration with the Great Barrier Reef Foundation with support from the Google Impact Challenge.

Crown-of-Thorns Starfish Control – Background

Crown-Of-Thorns Starfish (Acanthaster planci) are described as one of the most significant threats to the Great Barrier Reef. Since the 1960’s, land-based nutrient runoff has accelerated outbreaks of COTS which are destroying large areas of reef. With few natural predators, traditional control of COTS required manually injecting the starfish in excess of 10 times with a biological agent. In 2014, a new agent was released which was developed by the James Cook University (JCU) requiring only one injection per starfish. This advancement provided the stimulus for us to revisit automated (robotic) COTS population control and monitoring.

The agent, “bile salts”, is administered as an injection to the starfish with no residual effects on the environment. This starfish “control” is currently performed by human divers. The primary task of the COTSbot AUV, and now RangerBot, is to replicate diver-based injection of starfish by autonomously navigating complex reef environments and automatically detecting COTS on the coral and administer an injection.

Current achievements

  • 100% success rate in delivering coral larvae to damaged reefs
  • 99.4% accuracy in detecting COTS
  • Proven capabilities:
    • marine pest control and removal,
    • coral larvae capture and delivery to damaged reefs – capable of delivering 3 million larvae in 3 hours
    • underwater surveys and reef health monitoring
    • water quality testing
    • autonomous ‘swarming’ ability – robots controlled by one operator work autonomously and collaboratively to perform marine conservation tasks


Chief Investigators

Yellow underwater robot (COTSbot) in the ocean, with Dr Matthew Dunbabin on a research boat in the background