2021-22 Annual Report dashboard
Low numbers of COTS are sustainable on coral reefs; however, periodic population outbreaks significantly impact reef health and result in widespread loss of coral. The objective of the COTS Control Program is to protect coral on high-value reefs by suppressing COTS numbers to sustainable levels for coral growth and recovery through strategically targeted manual culling.
Key Performance Indicators and status of managed reefs
The dashboard below displays key performance indicators and the location and summary information for reefs that were managed by the COTS Control Program during the 2021-22 financial year.
Users can click the ‘select the map view’ buttons to view COTS outbreak status, live coral cover and culling activity metrics. Selecting a management area from the inset map (bottom left corner) will filter the map display and summary statistics to a geographic region. More detailed (reef-scale) information is revealed by hovering the cursor over a reef of interest.
- Management action categories are classified as follows:
- Culling, COTS unsustainable – Actioned reefs where COTS culling has occurred, but COTS numbers remain above the sustainable level for coral growth and recovery. Culling will continue until the target threshold is achieved.
- Culling, COTS sustainable – Actioned reefs where COTS culling has occurred, and COTS numbers were reduced to a sustainable level of coral growth and recovery. Monitoring surveys will continue to ensure timely action if COTS outbreaks re-emerge.
- Culling suspended, unsustainable – Actioned reefs where COTS culling was conducted, but numbers were too high to be effectively managed. Some targeted culling may occur in future, but resources have currently been diverted from these reefs. Monitoring surveys will continue to track the COTS outbreak and coral dynamics.
- Surveyed, remains sustainable – Actioned reefs where COTS and coral surveys were conducted, and COTS numbers are sustainable for coral growth and recovery. Monitoring surveys will continue to ensure timely action if COTS outbreaks re-emerge.
- Surveyed, COTS detected – Actioned reefs where surveys detected COTS outbreaks. Cull operations will commence when resources are available.
COTS outbreak status
Outbreak status is assigned to all managed reefs. It is calculated as the average number of COTS recorded across all manta tow surveys conducted at each reef, and it is expressed as COTS/tow (2,000 m2 survey area).
Tracking changes in outbreak status through time provides an indication of the progress achieved by the COTS Control Program.
- Outbreak status classifications are defined as follows:
- No COTS Detected – Manta tow surveys recorded no COTS or COTS feeding scars.
- No Outbreak – Manta tow surveys recorded 0 - 0.1 COTS/tow.
- Potential Outbreak – Manta tow surveys recorded 0.1 - 0.22 COTS/tow.
- Established Outbreak – Manta tow surveys recorded 0.22 - 1 COTS/tow.
- Severe Outbreak – Manta tow surveys recorded > 1 COTS/tow.
It is important to note that COTS often aggregate for both feeding and spawning, and this can result in large variability in COTS density estimates among individual manta tow surveys.
Although average COTS numbers are low on ‘No Outbreak’ reefs, there may be specific sites on these reefs where COTS numbers are above sustainable levels, and targeted culling is required to protect coral.
Hovering the cursor over individual reefs provides additional information on reef-specific COTS outbreak status estimates and manta tow tracks. The last survey date for 2021/22 is also displayed.
Live Coral Cover
‘Percentage categories of live coral cover’ (see bar chart in the upper right corner) are the average coral cover estimates generated from manta tow surveys at each managed reef.
Tracking changes in coral cover status through time provides an indication of the coral protection outcomes achieved by the COTS Control Program and helps to quantify other cumulative impacts on reef health.
Estimates from Reef Health Impact Surveys (RHIS) are also provided in the summary statistics panel.
The RHIS method usually produces a higher estimate of coral cover than manta tow surveys due to its smaller survey area and focus on shallow reef habitats which tend to support higher coral cover than deeper reef slope habitats surveyed using manta tow.
Live coral cover values presented in the summary statistics panel are aggregated average estimates for the 2021/22 financial year (Reef-wide and filtered to management area when selected).
Hovering the cursor over individual reefs provides additional information on reef-specific coral cover estimates from both manta tow and RHIS data.
The last survey date for 2021/22 is also displayed.
‘Catch per unit effort (CPUE)’ is the total number of COTS culled divided by the number of diver minutes spent searching for and culling COTS. The catch per unit effort is categorized as follows:
0.00 - 0.02 COTS/min: COTS, while present, have been reduced to densities where coral growth outpaces COTS predation. COTS spawning success may be suppressed.
0.02 - 0.04 COTS/min: COTS have been reduced to densities where coral growth outpaces COTS predation on reefs with < 40% live coral cover.
0.04 - 0.08 COTS/min: COTS have been reduced to densities where coral growth outpaces COTS predation on reefs with > 40% live coral cover.
0.08 - 0.2 COTS/min: COTS are above sustainable densities, and coral loss due to COTS predation increasingly outpaces coral growth.
> 0.2 COTS/min: COTS are well above sustainable densities, and rapid coral loss due to COTS predation occurs (coral loss to below 5% live cover is expected within 12 months).
Catch per unit effort values presented in the summary statistics panel are aggregated average estimates for the 2021/22 financial year (Reef-wide and filtered to management area when selected).