Summary
- Ten reefs were surveyed in the Capricorn-Bunker sector.
- Sector-wide hard coral cover was very high (50-75%).
- Hard coral cover had increased on eight reefs and had declined on two reefs.
- Low levels of crown-of-thorns starfish (COTS) were recorded at one reef.
- Low levels of hard coral bleaching were observed on seven of the ten reefs.
- Surveys for the 2021 report year in the Capricorn-Bunkers are complete.
- Trends in coral and fish communities surveyed on fixed site surveys are included at the bottom of the page.
Hard Coral Cover 0-10% 10-30% 30-50% 50-75% 75-100%
Figure 1: Map showing location of reefs in the Capricorn-Bunker sector. Click the points for more information.
Table 1: Overview of results obtained from manta tow surveys of reefs in the Capricorn-Bunker sector
| Capricorn Bunkers Sector | Summary | Trend since last survey |
|---|---|---|
| Average Coral Cover (%) | 52.5 | Increased |
| COTS status: | No Outbreaks | Stable |
| Coral bleaching: | Low | Stable |
As part of the Long-Term Monitoring Program (LTMP), manta tow surveys of hard coral cover and the abundance of the coral feeding crown-of-thorns starfish (COTS), Acanthaster cf. solaris were completed on ten reefs in the Capricorn-Bunker sector of the Great Barrier Reef (GBR) (Fig 1).
Preliminary results of the manta tow surveys are presented in Tables 1 and 2. The overall median hard coral cover for the sector was very high (50-75%) (Table 1) (Fig 2) and had increased since the most recent surveys in January 2020 (Fig 2).
Hard coral cover was very high (50 to 75%) on seven reefs, high (30 to 50%) on two reefs, and moderate (10-30%) on the remaining reef (Table 2). Since the previous surveys hard coral cover had increased on eight reefs, and declined on two reefs. Two COTS were recorded at Lady Musgrave Reef during manta tow surveys (Table 2). Sector-wide numbers of COTS were low and the trend was unchanged since previous surveys (Table 1, Fig 2). Low levels of coral bleaching were recorded, restricted to scattered individual colonies. Cases of coral disease were low on all reefs and within the range reported in previous years, as were numbers of the corallivorous snail, Drupella spp.
Table 2: Summary of manta tow surveys of reefs in the Capricorn-Bunker sector. Arrows indicate the trend in live coral cover and A. solaris since last survey; ▲ = increase, ▼ = decrease, " " = no change. Outbreak Status: NO no outbreak, PO potential outbreak >0.1 COTS per tow, IO incipient outbreak >.22 COTS per tow, RE recovering, AO = Active Outbreak>1 COTS per tow.
| Reef | Shelf Position | Tows | Previous survey year | Total A. solaris per reef | A. solaris per tow | A. Solaris Outbreak Status | Live Hard Coral Cover % | Soft Coral Cover % | Survey Year |
|---|---|---|---|---|---|---|---|---|---|
| BOULT REEF | Outer | 42 | 2020 | 0 | 0 ▼ | NO | 60.9 ▲ | 5.3 ▲ | 2021 |
| ERSKINE REEF | Outer | 21 | 2020 | 0 | 0 | NO | 36.7 ▼ | 3.1 ▼ | 2021 |
| FAIRFAX ISLANDS REEF | Outer | 38 | 2020 | 0 | 0 | NO | 52 ▲ | 6.3 ▲ | 2021 |
| HOSKYN ISLANDS REEF | Outer | 32 | 2020 | 0 | 0 | NO | 62.5 ▲ | 3.3 ▼ | 2021 |
| MAST HEAD REEF | Outer | 48 | 2020 | 0 | 0 | NO | 29.3 ▼ | 3.4 ▲ | 2021 |
| NORTH REEF (NORTH) | Outer | 29 | 2020 | 0 | 0 | NO | 47 ▲ | 7.1 ▼ | 2021 |
| ONE TREE REEF | Outer | 78 | 2019 | 0 | 0 ▼ | NO | 55.7 ▲ | 5 ▼ | 2021 |
| WRECK ISLAND REEF | Outer | 45 | 2019 | 0 | 0 | NO | 70.7 ▲ | 4.6 ▼ | 2021 |
| BROOMFIELD REEF | Outer | 54 | 2020 | 0 | 0 | NO | 59.1 ▲ | 5.7 ▲ | 2021 |
| LADY MUSGRAVE REEF | Outer | 66 | 2020 | 2 | 0.03 ▲ | NO | 50.5 ▲ | 3.3 ▼ | 2021 |
Figure 2: - Sector-wide changes in coral cover and the numbers of A. solaris for survey reefs in the Capricorn-Bunker sector of the GBR. Orange trend line = Hard coral. Purple bars = Crown-of-thorns (COTS)
Image 1. AIMS largest research vessel RV Solander, deploying the tenders for the survey team.
Image 2. Reefs with very high coral cover were predominant as seen at Wreck Reef.
Image 3. A bleached massive Porites at Erskine Reef. Some corals were still recovering from the 2020 coral bleaching event, the first to have significant effects on Southern GBR reefs.
Image 4. An AIMS diver conducting juvenile coral surveys at Broomfield Reef.
