Summary
- 10 reefs were surveyed in the Townsville sector.
- Sector-wide hard coral cover was moderate (10- 30%) and had increased since 2020.
- Hard coral cover had increased on nine reefs and had declined on one reef.
- No crown-of-thorns starfish (COTS) were recorded.
- Low levels of hard coral bleaching were observed.
Hard Coral Cover 0-10% 10-30% 30-50% 50-75% 75-100%
Figure 1: Map showing location of reefs in the Townsville sector. Click the points for more information.
Table 1: Overview of results obtained from manta tow surveys of reefs in the Townsville sector
| Townsville Sector | Summary | Trend since last survey |
|---|---|---|
| Average Coral Cover (%) | 27.3 | Increased |
| COTS status: | No Outbreaks | Stable |
| Coral bleaching: | Low | Decreased |
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 10 reefs were surveyed in the Townsville 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 moderate (10-30%) (Table 1) (Fig 2) and had increased since previous surveys in 2020 (Fig 2).
Hard coral cover was very high (50 to 75%) on one reef, high (30-50%) on two reefs, and moderate (10-30%) on seven reefs (Table 2). Since the previous surveys hard coral cover had increased on nine reefs and declined on one reef (Table 2).
Sector-wide numbers of COTS remained stable since previous surveys (Table 1, Fig 2). No COTS were observed.
Low levels of coral bleaching were recorded at nine reefs, restricted to scattered individual colonies.
Details of the manta tow method can be found in the Standard Operational Procedure No. 9 [AIMS Research - Crown-of-thorns Starfish and Coral Surveys - Standard Operational Procedure 9]. Further details of the Long-Term Monitoring Program can be found on the AIMS website.
Table 2: Summary of manta tow surveys of reefs in the Townsville 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 |
|---|---|---|---|---|---|---|---|---|---|
| KELSO REEF | Mid | 60 | 2020 | 0 | 0 ▼ | NO ▼ | 23 ▼ | 3.9 ▲ | 2021 |
| LITTLE KELSO REEF | Mid | 31 | 2020 | 0 | 0 ▼ | RE | 21.6 ▲ | 3 | 2021 |
| DAVIES REEF | Mid | 39 | 2019 | 0 | 0 ▼ | NO | 42 ▲ | 4.4 ▲ | 2021 |
| SAVILLE-KENT REEF | Mid | 60 | 2015 | 0 | 0 ▼ | NO | 16.9 ▲ | 3 ▲ | 2021 |
| WHEELER REEF | Mid | 22 | 2015 | 0 | 0 | NO | 70.5 ▲ | 4 ▲ | 2021 |
| DIP REEF | Outer | 51 | 2019 | 0 | 0 | NO | 18.8 ▲ | 3.7 ▲ | 2021 |
| MYRMIDON REEF | Outer | 50 | 2020 | 0 | 0 | NO | 37.5 ▲ | 4.4 ▲ | 2021 |
| JOHN BREWER REEF | Mid | 80 | 2020 | 0 | 0 | RE | 21.6 ▲ | 3.4 ▲ | 2021 |
| RIB REEF | Mid | 37 | 2020 | 0 | 0 | RE | 12.8 ▲ | 3.1 ▲ | 2021 |
| CHICKEN REEF | Outer | 45 | 2020 | 0 | 0 | NO | 28.4 ▲ | 3.6 ▼ | 2021 |
Figure 2: - Sector-wide changes in coral cover and the numbers of A. solaris for survey reefs in the Townsville sector of the GBR. Orange trend line = Hard coral. Purple bars = Crown-of-thorns (COTS)
Image 1. Moderate hard coral cover on the front of Chicken Reef where recovery of tabulate Acropora is conspicuous.
Image 2. Coral cover had declined since 2020 on Kelso Reef, most likely due to low densities of crown-of-thorns starfish.
Image 3. A school of parrotfish swimming amongst the abundant algae at Saville-kent Reef.
Image 4. Pocillopora and Acropora corals on the crest of the northern flank of Myrmidon Reef.
