Image courtesy of Wayne Osborn
Whale sharks (Rhincodon typus) are the world’s largest living fish and can grow to 18 meters, a weight of 34 tonnes and may live for 100 years. Found in tropical oceans around the world, each year from April to July, they gather at Ningaloo Reef in Western Australia. They can be found swimming close to shore, feeding in waters of less than 80 m deep and are a growing drawcard for tourists, who spend $11.6 million a year to swim with these docile giants at Ningaloo Reef.
For more than a decade, AIMS scientists have led research on whale sharks at Ningaloo. The AIMS Threatened Species/Megafauna team has mapped and tracked these animals using advanced satellite tags to examine their behaviour, feeding patterns, growth and migration.
The research has revealed some astounding information about these sharks. In Australia, several whale species migrate north from the Southern Ocean into the warm tropical waters of the north to breed during the winter months. Whale sharks can dive more than a kilometre deep and they migrate to the waters of neighbouring countries, thousands of kilometres of away.
Understanding these behaviours is critical to the future of the species. In order to ensure their survival we need to know what attracts these sharks to Ningaloo and where they go when they leave. Worldwide, whale sharks numbers are declining and in July 2016, the International Union for the Conservation of Nature upgraded the conservation status of whale sharks from ‘Threatened’, to `Endangered’.
It is likely that environmental stressors and human threats are putting the species at increasing risk of extinction. Whale sharks face problems of pollutants, a rise in ocean temperatures and acidification that are changing the physical structure and food networks in tropical oceans. These slow-moving creatures also continue to be fished and because they often swim close to the surface, can be accidentally killed by ships’ propellers.
Our research aims to identify the key threats and provide information to decision makers both nationally and internationally that can be used to improve the future of the species.
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