Quarterly Report – Q3 2020

For Quarterly report two (Q2) please click here.

Crown-of-thorns starfish Control Program: overview of progress

Dashboard description: This interactive display provides an overview of progress by the Crown-of-Thorns Starfish (COTS) Control Program since its expansion and the application of a new approach to pest management in November 2018.

The goal of the program is to protect coral on high value priority reefs throughout the Marine Park from COTS damage by reducing and maintaining COTS numbers at levels where their impact on coral is minimised. This dashboard highlights where these priority reefs are located, why they have been selected for pest management, and what management action has taken place. Achievements from the third quarter of 2020 (July to September 2020) are also highlighted. These achievements build upon the progress reported from previous periods.

Interactivity: Click on a segment of either "Management Area" or "Management Action" to filter information on the page. Use “CTRL + Click” to filter for both a Management Area and Management Action. CTRL + click the reset button in the bottom left corner to reset all filters.

Key performance summary

Overarching program:

  • COTS numbers have been managed at 195 high value priority reefs since November 2018.
    • Proactive monitoring has been conducted at 77 (39.5%) of the priority reefs to ensure COTS numbers are below levels that are sustainable for coral.
    • Culling activities have been conducted at 79 (40.5%) of the priority reefs to reduce COTS numbers to levels that are sustainable for coral.
    • Intensive management is currently underway at 39 (20.0%) of the priority reefs to achieve COTS numbers that are sustainable for coral.
    • COTS numbers are currently at sustainable levels for coral growth and recovery at 79.5% of priority reefs.
  • Of the 195 priority reefs:
    • 93 have been strategically targeted for pest management due to their high ecological value, including their capacity to spread coral larvae and support the recovery of surrounding reefs following impacts such as coral bleaching and tropical cyclones.
    • 40 have been targeted due to their high economic value, as they support significant tourism operations.
    • 62 have been targeted because they have both high ecological and high economic value.
  • Priority reefs are distributed throughout all regions of the Marine Park, however larger numbers of reefs have been managed in the Far Northern and Northern regions compared to the Central and Southern regions.
  • Due to currently high numbers of COTS on many reefs in the Central and Southern regions, fewer priority reefs can be actioned, as more time and effort is required at each reef to effectively manage COTS and protect coral.

Quarter 3, 2020:

  • Total number of high value priority reefs managed this quarter: 50
    • Vessel crews conducted manta tow surveillance across 1,005.7 kilometres of reef searching for signs of COTS activity.
    • Wherever signs of COTS activity were detected, dive teams were deployed to conduct more in-depth searches and to cull starfish.

Cull dive teams spent 3,012 dive hours searching for and culling COTS and culled a total of 12,561 starfish across 2,490 hectares of reef.

Tracking ‘Outbreak status’ on COTS Control Program priority reefs

Dashboard description: This interactive display shows the location of individual high value reefs managed by the COTS Control Program. The map panel on the left shows the ‘Outbreak status’ prior to the initiation of starfish management at each reef. The map panel on the right shows the most recent ‘Outbreak status’ determined for the reef since COTS management actions were initiated.

‘Outbreak status’ is determined based on the average number of COTS observed during manta tow surveys on a reef. Tracking changes in ‘Outbreak status’ provides an indication of progress achieved through pest management over time.

Reefs classified as ‘No Outbreak’ status (i.e. green dots) support COTS numbers that are below the defined thresholds that are sustainable for coral growth and recovery. It is important to note that this does not necessarily mean that the reefs are completely free of COTS. A reef may be assigned ‘No Outbreak’ status following a period of intensive management action to reduce COTS numbers to sustainable levels, or due to findings from proactive monitoring surveys that focus on identifying COTS outbreaks in their initial stages.

Interactivity: Select a management area on the left to filter maps and donut charts or zoom in to specific reefs and hover over a point to reveal additional summary information. CTRL + click the reset button in the bottom left corner to reset all filters. Click a map to hide the donut chart and inspect reef level information. Click outside of the map to make donut chart reappear. Maps are filtered to show reefs managed this quarter by default, toggle the “Managed this Period” button to show all of the reefs managed by the program to date.

Regional breakdown of COTS control progress:

  • During this reporting period (July to September 2020) COTS management effort focused on 50 high value priority reefs across the Northern, Central and Southern management regions of the Marine Park.
    • Pest management in the Northern region is important because this is the region of the Marine Park where major COTS outbreaks first emerge.
    • Pest management in the Central and Southern regions of the Marine Park is important because reefs in these regions currently have the highest numbers of COTS.

Far North:

  • No reefs were managed during this reporting period because previous surveillance showed very few or no COTS in this management region.

Northern:

  • 37 reefs in the Northern region were managed during this reporting period in order to maintain ‘No Outbreak’ status and suppress the development of a potential subsequent outbreak.
    • On 2 reefs (Lizard Island Reef and Round-Russell Reef) estimates of COTS numbers have transitioned from ‘No Outbreak’ to a ‘Potential Outbreak’ and intensive culling is underway to reduce COTS numbers.

Central:

  • 7 reefs in the Central region were managed during this reporting period, and from the commencement of pest management:
    • 2 reefs have transitioned from ‘Established’ outbreak to ‘No Outbreak’ due to intensive COTS management.
    • 2 reefs (John Brewer Reef and Keeper Reef) transitioned from ‘Severe’ outbreak to ‘Potential’ and ‘Established’ outbreak due to intensive COTS management.
    • Intensive pest management is continuing at Big Broadhurst Reef where COTS remain at “Potential Outbreak” levels.
    • 2 reefs were maintained at ‘No Outbreak’ status following action to suppress the development of an outbreak.

Southern:

  • 6 reefs in the Southern region were managed during this reporting period, and since the commencement of intensive COTS management:
    • 2 reefs have transitioned from ‘Established’ or ‘Potential’ to ‘No Outbreak’ status.
    • 3 reefs have been maintained at ‘No Outbreak’ status due to action to suppress the development of an outbreak.
    • On 1 reef (Llewellyn Reef), estimates of COTS numbers have transitioned from ‘Potential’ to ‘Established’ outbreaks since initial surveillance. Control efforts on this reef will be ongoing until COTS numbers are reduced to sustainable levels.

Case Study: Bramble Reef

Dashboard description: The interactive display provides an overview of progress in COTS management at Bramble Reef. The map in the top panel shows the results from manta tow surveillance before the pest management process began, and the map on the bottom panel shows outcomes from the latest surveillance. Red dots on these maps indicate the locations where COTS were detected. Green dots indicate locations where no COTS were detected.

Catch-per-unit effort (CPUE) is tracked over time to assess progress in achieving COTS numbers that are sustainable for coral recovery, maintenance and growth. The graph on the top right panel shows the overall trend in CPUE over repeated visits to conduct culling at Bramble Reef. The dotted blue line on the graph is the target CPUE below which coral can be sustained. CPUE can be broken down by size class by CTRL + clicking the arrow in the top right.

The bottom right panel provides a summary of all COTS management effort that has occurred on this high value reef, as well as action during this particular reporting period.

Interactivity: CTRL + Click the arrow in the top right corner to toggle between overall CPUE and CPUE broken down by size. Hover over dots on the maps to see number of COTS observed, COTS scars and hard coral cover estimates. Zoom out (scroll) to see the location of Bramble Reef.

COTS Control on Bramble Reef

  • Bramble Reef is in the Central Great Barrier Reef east of Lucinda. Bramble Reef provides an example of the process of controlling and maintaining COTS numbers to levels that are sustainable for coral growth and recovery through intensive pest management.

What was the initial situation?

  • Initial manta tow surveillance in February 2019 revealed that Bramble Reef had an ‘Established’ outbreak, with a large aggregation of COTS along the sheltered back reef slope and also along the north east reef slope and crest region.
  • Initial Reef Health Impact Surveys (RHIS) estimated 15-24% hard coral cover at this reef, and a CPUE threshold of 0.04 was therefore established as the ecologically sustainable threshold for coral growth and recovery.

What did the program do?

  • Bramble reef was intensively culled during 23 repeat visits between March 2019 and February 2020 when the target CPUE threshold was achieved and the outbreak status was downgraded from ‘Established’ to ‘No Outbreak’.
  • Follow up surveillance and culling was conducted in August 2020 and confirmed that COTS numbers were below sustainable thresholds and remained at ‘No Outbreak’ status.
  • Control program divers spent a total of 1464 hours searching and culling 28,350 COTS during the 23 visits.

How is the situation now?

  • Minimal COTS activity was observed on the most recent surveillance voyage, prompting a targeted culling response to maintain low numbers of COTS.
  • Bramble Reef is scheduled to be re-visited every 3 – 6 months to ensure COTS numbers are maintained below threshold levels.

Case Study: Moore Reef

Dashboard description: The interactive display provides an overview of progress in COTS management at Moore Reef. The map in the top panel shows the results from manta tow surveillance before the pest management process began, and the map on the bottom panel shows outcomes from the latest surveillance. Red dots on these maps indicate the locations where COTS were detected. Green dots indicate locations where no COTS were detected.

Catch-per-unit effort (CPUE) is tracked over time to assess progress in achieving COTS numbers that are sustainable for coral recovery, maintenance and growth. The graph on the top right panel shows the overall trend in CPUE over repeated visits to conduct culling at Moore Reef. The dotted blue line on the graph is the target CPUE below which coral can be sustained. CPUE can be broken down by size class by CTRL + clicking the arrow in the top right.

The bottom right panel provides a summary of all COTS management effort that has occurred on this high value reef, as well as action during this particular reporting period.

Interactivity: CTRL + Click the arrow in the top right corner to toggle between overall CPUE and CPUE broken down by size class. Hover over dots on the maps to see number of COTS observed, COTS scars and hard coral cover estimates. Zoom out (scroll) to see the location of Moore Reef.

COTS Control on Moore Reef

  • Moore Reef is in the Northern Great Barrier Reef east of Cairns. Moore Reef provides an example of the process of controlling COTS numbers to levels that are sustainable for coral growth and recovery through intensive management.
  • Importantly it shows the Control Program’s ability to reduce the number of smaller COTS to help suppress the next primary outbreak.

What was the initial situation?

  • Initial manta tow surveillance at this reef in May 2020 suggested the reef was in “No Outbreak” status, however some feeding scars were observed in the northern back reef area. These observations triggered the commencement of intensive culling as per the Integrated Pest Management (IPM) Framework.
  • Initial Reef Health Impact Surveys (RHIS) estimated hard coral cover at 16 - 21%, and a CPUE threshold of 0.04 was therefore established as the ecologically sustainable threshold for coral growth and recovery.

What did the program do?

  • Moore reef was intensively culled during 8 repeat visits between May 2020 and September 2020, with divers spending a total of 534 hours searching and culling 1,821 COTS. Of these 1,821 COTS, 1371 (75.3%) were from the smallest size class (0 – 15 cm)
  • Between July and September 2019, cull effort was focused along the northern back reef and south western crest and bommie habitats, reducing CPUE from a peak of 0.1 (i.e. 4 COTS culled for every 40 minutes spent searching) down to an ecologically sustainable 0.03 (i.e. 1.2 COTS culled for every 40 minutes spent searching).

How is the situation now?

  • Tourism operators continue efforts to manage COTS on and near key tourism sites on Moore Reef.
  • Follow-up manta tow surveillance in September 2020 showed that the reef has been maintained at ‘No Outbreak’ outbreak status, yet COTS scars were still observed.
  • Moore Reef is scheduled to be re-visited every 3 – 6 months to ensure COTS numbers are maintained below threshold levels.
  • Due to the large numbers of smaller COTS removed from Moore Reef, COTS Control Program divers and surveyors are on high alert for signs of the emergence of smaller starfish in the initiation region between Cairns and Cooktown.
  • Controlling these emerging cohorts is deemed to be important in suppressing the build-up of the next primary outbreak.