Report on surveys of reefs in the Pompey and Townsville sectors of the Great Barrier Reef

Dates: 17^nd April to 15^th May 2014

Vessel: MV Cape Ferguson

Survey leader: Mike Emslie

Manta tow surveys for the 2014[1] survey year were completed on three reefs in the Pompey sector, and eight reefs in the Townsville sector of the Great Barrier Reef (GBR). Detailed surveys for benthic organisms, visual census of fishes and surveys for agents of coral mortality (scuba search) were made at the same reefs and a further three reefs in the Pompey sector (these reefs had been surveyed by manta tow previously on a recent trip, see here). Preliminary results of the manta tow and scuba search surveys are presented in this report.

Median reef-wide live coral cover on reefs surveyed in the Pompey sector had increased or remained similar to that recorded during previous surveys, with moderate (10-30%) median reef-wide live coral cover (hereafter coral cover). No crown-of-thorns starfish (COTS) were recorded during manta tow surveys. Reefs in this sector are in the early stages of recovery following widespread destruction by Severe Tropical Cyclone Hamish in March 2009. Some recent cyclone damage was observed on Tern Island Reef likely due to Cyclone Ita that passed through the region as a Category 1 storm in April 2014.

Coral cover was generally low on reefs surveyed in the Townsville sector; between 0-5% on two reefs, 5-10% on five reefs and 10-20% on one reef. Despite the generally low coral cover the majority of reefs in the Townsville sector were showing early signs of recovery from Severe Cyclone Yasi that passed passed to the north of the sector in early February 2011. Small numbers of COTS, well below outbreak levels, were recorded on three reefs in the Townsville sector during manta tows.

Large numbers of COTS were seen in scuba searches at Reef 21-060 in the Pompey sector; this was not surprising, as recent manta tow surveys indicated an Active Outbreak on this reef. Low numbers of COTS were also observed during scuba searches on three reefs in the Townsville sector (Fore and Aft, Little Kelso and Chicken). The COTS were generally small (15-25cm). More importantly there was a marked increase in the counts of small COTS feeding scars on all three reefs as well as Kelso and Roxburgh Reefs. These scars were generally on small coral colonies and suggest that COTS recruitment may be underway on reefs in this sector. Signs of coral disease, bleaching and counts/scars of Drupella spp. on the reefs in both sectors that were surveyed using scuba were generally similar to or less than those recorded in previous surveys.

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]. For a full explanation of COTS outbreak terminology refer to the following web-page: Crown-of-thorns on the Great Barrier Reef.

Perimeters of three reefs were surveyed using manta tow (Table 1). Sites on each of these reefs and on three other reefs were also surveyed in detail using scuba (Table 2). No COTS were recorded during manta tows. The majority of reefs in this sector were heavily damaged by Cyclone Hamish in March 2009. Surveys in 2014 found evidence of recovery in coral cover on Pompey Reef (No. 2) that was moderate (10-20%) compared to the low cover when last surveyed in 2012. Coral cover at Reef 21-591 and at Tern Reef was unchanged. Some signs of mechanical damage to corals were seen during manta tows of Tern Reef, such as recently broken corals at the base of the reef slope on the flanks. This was probably due to the effects of Cyclone Ita that passed near this reef as a category 1 storm in April 2014, just prior to these surveys

Table 1. Summary of manta tow surveys for reefs in the Pompey sector.

Table 2. Summary of SCUBA search survey results for the Pompey sector.

I=inner, M=mid, O=outer, WS = White Syndrome, BBD = Black Band Disease, BrB = Brown Band Disease, SEB = Skeletal Eroding Band Disease.

Scuba searches (Table 2) found incidence of disease was generally unexceptional (high levels of WS on Pompey Reefs 1 and 2 were similar to those seen on these reefs in previous years). High counts of COTS on Reef 21-0560 show that a COTS outbreak that has affected this reef since 2010 is continuing.

For more information on coral disease refer to the AIMS web site at:

AIMS Long Term Monitoring - Coral Diseases on the Great Barrier Reef - Introduction

Perimeters of eight reefs were surveyed using manta tow (Table 3). Sites on these reefs were also surveyed in detail using scuba (Table 4). COTS were recorded during manta tow surveys at three reefs; in each case only a single COTS was seen, and all three reefs, Fore and Aft, Kelso and Fork, remained classified as Recovering. Coral cover on survey reefs has either remained stable or has increased since the last survey. Reefs in the region are still in the early stages of recovery from the effects of Severe Tropical Cyclone Yasi, a category 5 system that passed just north of this sector in January 2011. At that time most reefs in the sector already had a low coral cover and were in the early stages of recovery from COTS activity between 1999 and 2006. Increases in coral cover were recorded at Fore and Aft Reef, Fork Reef, Knife Reef, Little Kelso Reef and Roxburgh Reef. The highest coral cover was at Little Kelso Reef.

Table 3. Summary of manta tow survey results for the Townsville sector.

Scuba searches found small numbers of COTS on three reefs (Kelso, Fore and Aft and Fork). Manta tow surveys did not record COTS on two of these reefs (Kelso and Fork) though feeding scars were present. In total, COTS were seen at five of the eight reefs that were surveyed. The COTS observed during scuba searches on Fore and Aft and Fork Reefs were small (5 - 15cm in diameter) suggesting that they had settled on these reefs as larvae sometime in the last two to three years. Scuba searches also found many small coral colonies (~10 cm diam.) that appeared to have been recently consumed, though no COTS were found nearby. This suggests that many more small COTS may be hidden in the reef framework and emerging to feed at night. Taken together, these observations would suggest that mid and outer shelf reefs in this sector may be experiencing a period of COTS recruitment, and the numbers of adult COTS can be expected to increase in coming years. Scuba searches on reefs in this sector found a low incidence of coral disease. Similarly, Drupella spp. were observed on seven reefs (all except for Chicken Reef) but in numbers that would not be considered exceptional.

Table 4. Summary of SCUBA search survey results for the Townsville sector.

M=mid, WS = White Syndrome, BBD = Black Band Disease, BrB = Brown Band Disease, SEB = Skeletal Eroding Band Disease.