What is the short-term strategy?
The current crown-of-thorns starfish outbreak is largely limited to the northern part of the Reef. However, based on previous population increases, the outbreak is likely to move south in the coming years.
When densities of the starfish have reached the point where they are eating coral faster than it can grow, management intervention is needed. The manual control of crown-of-thorns starfish, using an injection of approved solutions, has occurred on the Great Barrier Reef since the 1980s.
To address the current outbreak, the Australian Government funds a crown-of-thorns starfish management program, which involves manually injecting starfish to protect coral cover on priority reefs, particularly prime tourism sites.
The program involves dedicated dive teams from the Association of Marine Park Tourism Operators, with support from the Queensland Parks and Wildlife Service and the Great Barrier Reef Marine Park Authority. In 2014 the Reef and Rainforest Research Centre also joined management efforts.
The control program is made up of three elements:
- Intelligence and dedicated surveillance to detect crown-of-thorns starfish and assess coral health
- A highly trained control team to cull the starfish using injection methods and to assess changes in coral health
- A comprehensive reef health database to monitor effectiveness of control efforts and adaptively manage the program.
The Queensland Parks and Wildlife Service (QPWS), through the jointly funded state and Commonwealth Field Management Program, undertakes extensive broadscale surveillance of crown-of-thorns starfish populations on individual reefs.
Between 2012 and 2014, QPWS surveyed all mid-shelf reefs between Cairns and Lizard Island (more than 120 reefs) and conducted more than 8000 manta tows and 2400 reef health and impact surveys.
These surveys are shared with dive teams culling the starfish, helping to direct efforts and resources.
Researchers, tourism operators and the public also provide sightings of crown-of-thorns starfish through the Eye on the Reef program.
Manual injection (control) of crown-of-thorns starfish
Manual injection of the crown-of-thorns starfish is carried out by trained divers deployed by the Association of Marine Park Tourism Operators through a contractual agreement with the Great Barrier Reef Marine Park Authority.
The association also trains tourism operators and community-based organisations that have a permit and the appropriate insurance to search for and lethally inject the coral-eating starfish.
In 2012, researchers from the ARC Centre of Excellence for Coral Reef Studies developed a new innovative single-injection method that uses a bile salts solution. Comprehensive laboratory and field trials undertaken before large-scale use of this method on the Reef in 2013 showed no observable adverse effects on the ecosystem.
In 2016, researchers from James Cook University also tested single-injections of household vinegar for use in crown-of-thorns starfish control and found it is also highly effective at culling this coral-eating pest. A subsequent field impact assessment undertaken in partnership with the Great Barrier Reef Marine Park Authority showed that this method is also safe for use in the Marine Park.
In addition to these two single-injection methods, multi-injections of sodium bisulphate are also endorsed for use in crown-of-thorns starfish control on the Great Barrier Reef. Single-injection methods can result in a two and a half fold efficiency gain compared to a multi-injection method, allowing dive teams to inject more starfish and cover more of the Reef during a single dive. However, increased efficiency between single and multi-shot methods will always be dependent on the density of starfish. Where starfish densities are low, the efficiency difference between single and multi-shot methods will be negligible.
Details on how to administer these injections and conduct effective crown-of-thorns starfish control is provided in the Crown-of-thorns starfish control guidelines. Use of these methods is available to people who obtain a permit from the Great Barrier Reef Marine Park Authority. There is no assessment fee for a crown-of-thorns starfish control permit.
The prevalence of crown-of-thorns starfish is monitored through programs such as the Field Management Program, the Australian Institute of Marine Science’s long-term monitoring program and our Eye on the Reef program.
Data about crown-of-thorns starfish populations is entered into the agency’s Eye on the Reef database, enabling the effectiveness of the control program to be assessed and to help decide which sites need to be revisited and how often.
A number of prime tourism reefs have also been selected for long-term monitoring to establish the change in coral cover over time.
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