Fish and benthic community surveys of Elizabeth Reef in the Elizabeth and Middleton Reefs National Nature Reserve (Tasman Sea)

Full description

Fish, benthic and bêche-de-mer surveys were carried out on Elizabeth Reef in the Elizabeth and Middleton Reefs National Nature Reserve between the 2nd and 6th December 2003. 10 sites were surveyed, which encompassed three major habitat areas with different levels of exposure to oceanic conditions; sheltered lagoon (site 1), reef channel or near reef channel (sites 2 and 8) and exposed reef slopes (other seven sites). Reef slope sites were distributed evenly around the perimeter of Elizabeth Reef to encompass any local variation in reef communities due to reef orientation. The abundance of bêche-de-mer and clams were also assessed at all sites. Due to diving restrictions, surveys were limited to depths of around 9m.Species level data and crude abundance estimates of the benthic communities were obtained using a rapid visual assessment protocol (RAP). Video transect surveys were used to obtain more rigorous abundance estimates of biota at a finer taxonomic resolution.Species composition data and crude abundance estimates of the fish communities were obtained using a timed swim, rapid visual census method. Visual census transects provided more rigorous density estimates of a select group of species and a solid baseline for future monitoring surveys.Thirteen species of Holothuria (bêche-de-mer), crown of thorns starfish (COTS) and giant clams (Tridacna gigas and Tridacna derasa) were surveyed in the lagoon and on the reef perimeter at depths of 6-12m. The lagoon was sampled using SCUBA searches and snorkel swims and the reef perimeter was sampled using SCUBA searches. SCUBA searches, along transects, were used to provide information on numbers of COTS in defined size classes, COT scars, Drupella (a coral eating snail) and other sources of coral mortality including coral bleaching and coral disease. Species level data and crude abundance estimates of the benthic communities were obtained using a rapid visual assessment protocol (RAP). Video transect surveys were used to obtain more rigorous abundance estimates of biota at a finer taxonomic resolution.
This research was undertaken as part of a monitoring program, which will be used to determine the effectiveness of management practices within the National Nature Reserve.
The Elizabeth and Middleton Reefs Marine National Nature Reserve is one of two protected areas in the Tasman Sea region. The Reserve is located approximately 600 km east of Coffs Harbour and 200 km north of Lord Howe Island. The Reserve covers an area of 188,000 hectares, and includes the southern-most open-ocean platform reefs in the world: Elizabeth Reef (~5,100 ha) and Middleton Reef (~3,700 ha). Formed on volcanic seamounts in the northern Tasman Sea, these isolated reef systems lie close to the boundary between the Coral Sea and the Tasman Sea and are exposed to both tropical and temperate ocean currents. The Reserve was proclaimed on 23 December 1987. The Reserve management plan states that the reefs are to be managed as strict nature reserves - World Conservation Union (IUCN) category Ia. Such reserves are primarily for scientific research to ensure habitats, ecosystems, and native species are preserved in as undisturbed state as possible. The Reserve also forms part of the National Representative System of Marine Protected Areas (NRSMPA).

Lineage

Maintenance and Update Frequency: notPlanned

Statement: Statement: The following is a list of references for the survey protocols used in this project:1. Benthic Rapid Assessment Protocol (RAP):DeVantier LM, De'ath G, Done TJ, Turak E (1998) Ecological assessment of a complex natural system: A case study from the Great Barrier Reef. Ecological Applications 8: 480-496.2. Video Transect Surveys:Page C, Coleman G, Ninio R, Osborne K (2001) Surveys of benthic reef communities using underwater video. Long-term Monitoring of the Great Barrier Reef, Standard Operational Procedure No. 2, Australian Institute of Marine Science, Townsville.Osborne K, Oxley WG (1997) Sampling benthic communities using video transects. pp 363-376. In: English S, Wilkinson C, Baker V (eds) Survey manual for tropical marine resources. 2nd Ed. Australian Institute of Marine Science.3. Fish Rapid Visual Census Method:The rapid visual census method used was a timed swim count modified from that described in "Williams DMcB (1982) Patterns in the distribution of fish communities across the central Great Barrier Reef. Coral Reefs 1: 33-43."4. Fish Visual Census Transects:Halford A, Thompson AA (1994) Visual Census Surveys of Reef Fish. Standard Operational Procedure 3. AIMS Townsville.English S, Wilkinson C, Baker V (eds) (1997) Survey Manual for Tropical Marine Resources. 2nd edition. Australian Institute of Marine Science, Townsville. 402pp.Other Survey Methods:Snorkel swims were used to survey the shallow water of the reef lagoon. Each observer censused a 500m by 5m belt transect, covering 2500 m2 of substrate. The four observers swam side-by-side, approximately 10m apart. Observers recorded numbers of bêche-de-mer, COTS and clams. The transect length was determined by marking a waypoint on entry and then having the tender proceed 500m from this waypoint (judged by the GPS distance from the original waypoint), drop a buoy and standby. The snorkellers were able to observe the tender and swim towards it. Water depths ranged from 2-6m. The latitude and longitude of the start and end point transect were recorded (using a GPS) to assist in future surveys of the same area.SCUBA searches provided a more detailed picture of the causes and relative scale of coral mortality than was possible with the video technique. A 5m belt (2.5m either side of the central tape measure) was visually searched along each 50m transect for holothurians. Along the same transects, from a 2m wide belt (1m either side of the central tape measure), data were recorded for the categories listed below:Crown of thorns starfish - Total count in 3 size classesCrown of thorns starfish scars - Total countDrupella spp - Total countDrupella scars - Total countWhite syndrome disease scars - Total countBlackband disease scars - Total countUnknown scars -Total countCoral bleaching- Estimate of bleaching as a percentage of live coral cover on the transect.

Notes

Credit
Sweatman, Hugh PA, Dr (Custodian)