They are the gentle giants of the ocean, weighing as much as 1400 kilograms. But an emerging market in Chinese medicine for gill rakers is threatening global populations of giant manta rays.
Now, amid increasing international efforts to curb the decline, the federal government will today protect the species - found predominantly in the tropical waters of northern Australia - under national environment law.
Under the protections, the giant ray will be listed as a migratory species, making it an offence to take, trade, keep, or move the species from Commonwealth waters. Fishers will now also have to report any interactions with a giant manta ray as is the case with other protected species such as dugongs and whale sharks.
Environment Minister Tony Burke said while Australia's populations of giant manta rays were fairly secure, globally the species' numbers have declined 30 per cent. Last year, the giant manta ray was listed as threatened under the international Convention on the Conservation of Migratory Species. The International Union for the Conservation of Nature also rates the species as vulnerable to extinction due to overfishing.
''The giant manta ray is a highly migratory species - with some being known to travel more than 1000 kilometres - and threats often arise outside of protected areas,'' Mr Burke said.
''For this reason, the Convention on the Conservation of Migratory Species and our national environment law are an excellent way to achieve international co-operation and co-ordination to better protect the species.''
An investigation last year found the main driver of the manta ray's decline is rapidly increasing demand from Chinese and other markets for gill rakers - thin filaments that rays use to filter food from water - to be dried and boiled as medicines.
The group's report found gill rakers were fetching on average $US251 a kilogram in Guangzhou in southern China, where 99 per cent of the world's product is sold. Targeted fishing of rays occurs predominantly in India, Sri Lanka, Indonesia, Peru and China.
The report says local traders are spruiking gill rakers as a way to boost the immune system, while others claim it can treat ailments like chickenpox and even cancer.
Murdoch University manta ray researcher Frazer McGregor said the increasing affluence of the Chinese market was driving demand in animal products and the manta ray had been affected. He said the danger to the species was intensified by its slow rate of reproduction.