UWA and AIMS discover parasites storing ‘black box’ of information on whale sharks’ diet in Ningaloo

Researchers at The University of Western Australia and the Australian Institute of Marine Science (AIMS) made breakthrough discoveries this month, finding the copepod parasite acts as a ‘black box’ of information about the diet of the giant whale shark.

Whale Sharks feed at night, and in deep water, which made tracking their consumption difficult and encouraged researchers to turn to the isotopic approach.

Lead researcher Brendon Osorio, a recent graduate from UWA’s School of Biological Sciences, said carbon and nitrogen isotope compositions were analysed from whale shark skin and the copepods, with nitrogen showing a strong correlation.

“Our results suggest the nitrogen composition of parasitic copepods provides a reliable and accurate proxy of the whale sharks’ diet integrated over both time and space,” Mr Osorio said.

“Understanding diet and foraging habitats within these sites is important for strategies to manage and conserve the populations.”

Adjunct Senior Research Fellow Dr Mark Meekan, from UWA’s Oceans Institute, said threats to the species’ existence included hunting, ship strike, pollution and climate change, which could impact the distribution of the plankton that whale sharks feed on.

“A better understanding of the life history and ecology of copepods is still required, but the latest study had shown copepods to be an accurate and less invasive method of diet analysis than biopsies,” Dr Meekan said.

The largest filter-feeding fish in the world, the whale shark is listed as endangered under the International Union for Conservation and Nature’s Red List.