#COTS

The Pacific crown-of-thorns starfish (COTS; Acanthaster cf. solaris) is a coral eating starfish that is native to the Great Barrier Reef.

A single adult COTS can consume approximately 10m2 of coral per year, and under normal conditions, the level of coral predation by COTS can be sustained with no apparent long-term reef degradation. However, when COTS population numbers increase out of the normal range, they can reach densities where the COTS eat coral tissue at a rate faster than the coral on the Reef can grow. This population increase is known as a COTS outbreak, with the Reef currently experiencing its fourth major recorded outbreak. 

COTS outbreaks cause significant damage to coral reefs across large spatial scales, and are one of the major causes of coral decline across the Great Barrier Reef over the past 40 years. Minimising the impact of outbreaks is considered one of the most scalable and feasible direct management interventions available today to enhance the Great Barrier Reef’s health and resilience in the face of climate change.

The Foundation's Reef Trust Partnership COTS Control Component focuses on efforts to control COTS with the goal to expand and improve COTS management to reduce coral mortality from secondary outbreaks at high ecological and economic value coral reefs in the short-term with a view to achieving better prevention and/or suppression and containment of primary outbreaks in the near to medium-term.



#Focus areas


Support existing in-water COTS control and drive towards improved efficiency


Lead a step change in surveillance for early COTS detection and early intervention


Explore alternative control methods to address COTS management at a broad scale in the future


#COTS Control Program

Manual culling of COTS is currently the only option available to protect coral from outbreaks.

From 1 July 2020, the COTS Control Program is being delivered as a strategic partnership between the Foundation, Great Barrier Reef Marine Park Authority and Reef & Rainforest Research Centre. The program is delivered by professionally trained divers that undertake strategic surveillance and culling in order to protect coral. The delivery of the program is underpinned by the best available science, including a custom-built decision support system that enables data-driven decision making on the water.

An independent review of the COTS Control Program from 2012 to 2019 highlighted the continuous improvement in program delivery over time. The reviewers concluded that “…the current iteration of the COTS Control Program under the guidance of the Integrated Pest Management Strategy provides a strategic and conservative approach to the application of best available science and best practice”.

The full report is available here.

#COTS Control Innovation Program

​Recognising that manual control of COTS during outbreaks is not, on its own, an ideal long-term solution, the Reef Trust Partnership has established the COTS Control Innovation Program (CCIP), managed as a consortium, to create a step-change and accelerate the development of innovative control and surveillance methods while continuing to improve the efficacy and efficiency of current methods.

The proposed program is based on two independent phases:  

  1. A CCIP Feasibility and Design Phase (12 months), focused on assessing the feasibility (technical, social and regulatory) and modelling the benefit (impact) at scale of a broad range of possible improvements and interventions. Applying a transparent and consistent scientific framework, this phase will lead to recommendations on priority areas that should be further investigated and developed;  
  2. A targeted CCIP (36 months), giving effect to the recommendations of the feasibility and design phase, and identifying pathways for implementation and integration into the COTS control program.   

#Long-term funding strategy for COTS control

Effective action on COTS predation will be one of the strongest levers to protect coral cover in the coming decades, therefore a long-term approach to sustained funding is imperative.  

A funding strategy that presents a comprehensive business case and real options to support planning and policy development for long-term funding of COTS management will be delivered.