Monitoring the ecological effects of the 2004 rezoning of the Great Barrier Reef Marine Park

In July 2004, the Great Barrier Reef Marine Park was rezoned to better protect the Great Barrier Reef's biodiversity. This increased the area of Marine National Park Green Zones from less than five per cent to 33 per cent of the Marine Park. Extractive activities such as collecting and fishing are not allowed in Green Zones whereas other types of zones permit these activities. Scientists have embarked on a major research program to monitor the ecological effects of the rezoning. This research is funded by institutions such as the Marine and Tropical Sciences Research Facility, James Cook University (JCU) and the Australian Institute of Marine Science (AIMS).

The rezoning monitoring program

Scientists from James Cook University and the Australian Institute of Marine Science are carrying out the rezoning monitoring program. The program currently involves three core projects focused on reef fish populations on:

  1. Near-shore reefs 
  2. Mid-shelf and offshore reefs
  3. Inter-reefal shoal country. 

1. Near-shore reefs monitoring project (JCU)

This project compares fish populations in Blue and Yellow Zones (where fishing is allowed) and in Green Zones on island fringing reefs.

Sites

Surveys are conducted at 100 sites located on reefs around Magnetic Island, the Palm Islands, the Whitsunday Islands and the Keppel Islands. Fifty of these sites are located in zones that have been and are still open to fishing, 32 sites are in areas which have been Green Zones since 1987, and another 18 sites are in zones that became Green 'no-take' Zones in July 2004. Additional sites will be added in 2008 north of Hinchinbrook Island and between the Whitsundays and Shoalwater Bay. 

Methods

Diver surveying the reef
Divers conducting Underwater Visual Census (UVC) of fish species and benthic organisms

Each site is surveyed at the same time each year. At each site, the survey team carries out an underwater visual census (UVC). The UVC technique is a standard monitoring method used for reef fish surveys around the world. This technique involves experienced SCUBA divers swimming along a 50m transect at certain depths, counting numbers of fish seen along each transect and recording their size. Although 150 species of reef fish are surveyed, the analysis has been focused on coral trout (Plectropomus spp.), fishes that are coral trout prey, and fishes of particular interest such as stripey sea perch (Lutjanus carponotatus). The biological characteristics of the coral reef are also recorded.

Timing

This monitoring program was established between 1999 and 2002 in established Green Zones and Blue Zones of the Palm, Whitsunday and Kepppel Island groups.  Additional baseline surveys of all sites were completed between November 2003 and June 2004 before the new Zoning Plan came into effect. This allows a comparison of fish populations before and after the Plan was introduced. Monitoring in some of these sites dates back to 1983 allowing scientists to compare current trends with trends seen over the last 20 years. Follow up surveys were conducted at each site in 2006 and 2007. A fourth round of surveys will be conducted throughout 2008.

2. Mid-shelf and offshore reefs monitoring project (AIMS)

Map showing rezoning monitoring sites
Figure 1: Map showing study sites. Pairs of Blue and Green Zones in five sectors make up the offshore design monitored by the AIMS. Inshore Blue and Green Zones are monitored by JCU

This project compares fish populations at sites in Blue Zones and new Green Zones on mid-shelf and offshore reefs.

Sites

Surveys are based on comparing pairs of reefs, with each pair being one Blue Zone reef and a nearby Green Zone reef. Six reef pairs are located in each of the following regions, Cairns-Innisfail, Townsville, Mackay and the Swain reefs. Four reef pairs are located in the Capricorn Bunker group totalling 56 reefs. Three sites are surveyed on each reef, totalling 168 sites across the Marine Park.

View Figure 1: Map showing study sites

Methods

Each site is surveyed using the same underwater visual census (UVC) technique used in the near-shore reef monitoring project. SCUBA divers swim along 50m transects at certain depths and count numbers of fish seen along each transect. The analysis is focused on coral trout (Plectropomus spp.). Fish size and the biological characteristics of the coral reef at each site are also recorded.

Timing

The first round of surveys began in 2005, and surveys continued in different regions throughout 2006.

Region

Timeline

Cairns-Innisfail
October to December 2005
Townsville
Seven reefs surveyed between November 2005 and July 2006
Mackay
March to July 2006
Swains reefs
January 2006
Capricorn-Bunker Group
March to May 2006

Surveying the remaining five reefs in the Townsville sector is planned.

3. Inter-reefal, shoal areas (AIMS/JCU joint project)

This project compares fish populations on shoals in Blue Zones and new Green Zones. Shoals are submerged features such as rocks, sponge gardens, patches of deep-water algae Halimeda or even patches of particular types of sand or gravel lying a few centimetres higher than the surrounding seabed. This can make shoals very difficult to find, and they may be located in waters too deep to survey by SCUBA. Differences in their structure, size and topography may also affect the types of fish present, their numbers and their size. This means that it is harder to identify suitable survey sites and different technology must be used to survey these fish populations.

Sites

The first step is to find pairs of shoal country sites that have similar characteristics and are in the same area, but lie within different Marine Park zones. Once located, the shoal sites need to be mapped to determine their physical characteristics. If mapping shows that the blue and green shoals have a similar structure and can be compared, they are listed as survey sites and fish surveys can commence.

Shoal monitoring sites are currently being identified. Information has been collected from fishermen and scientists about where suitable shoals can be found. Potential sites off Townsville (the Magnetic shoals) and Hinchinbrook Island (the Brook shoals) have been investigated and mapped. In the Magnetic and Brook shoals, three sites have been identified as Blue Zone surveys sites, and three as Green Zone survey sites. Sites in four other regions, off Cairns, Bowen, Rockhampton and Gladstone are being explored.

Timing

Magnetic and Brook shoals were surveyed in mid 2006 and the Cairns region was surveyed in December 2006. It is also planned to survey the remaining regions.

Methods

Shoal mapping

Potential shoal sites are located and mapped using a multibeam echo sounder. This instrument provides a high-resolution 3D map of the site showing topography to a scale of tens of centimetres.

Habitat characterisation

Physical features identified are explored with a drop camera to determine habitat and community structure. It is important that sites are similar both physically and biologically.

Fish census

Once shoals are mapped and characterised, fish populations are surveyed using a Baited Remote Underwater Video (BRUV). This equipment uses a fixed bait bag and underwater videos to record the types of fish and their approximate numbers. BRUVS can also be adapted with two cameras that allow fish size to be measured to an accuracy of 5mm.

 

Results so far

While it will take many years for the full effects of the rezoning to appear, some early effects have been observed.

Near-shore reefs

In the Whitsundays, coral trout density and biomass (an indicator of their average size) have increased by 1.7 times since the rezoning. Increases were only seen in Green Zones, suggesting that it was the change in zoning and not some other reef wide factor that has caused the increases. Data from the Palm Islands, the Keppel Islands and Magnetic Island are still being analysed.

Mid-shelf and offshore reefsreportof_effects_of_rezoning_screenshot

Surveys of twenty five reef pairs in the Cairns-Innisfail, Mackay, Swains and Capricorn-Bunker reefs showed that while coral trout numbers and biomass varied between different regions, all regions showed the same trend with trout numbers and biomass being between 1.3 and 1.7 times higher in Green Zones established in 2004 than in Blue Zones. The researchers also found that at reefs where long term data was available, trout numbers in Blue Zones were similar to those recorded over the last ten years. This indicates that the pattern has arisen from increases in trout numbers in Green Zones, and not decreases in trout numbers in Blue Zones.

View the independent report, 'Surveys of the effects of the rezoning of the Great Barrier Reef Marine Park in 2004 on some fish species-preliminary findings'.

Results from the program have also been published as a scientific papers in 2008:

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