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Sharks’ role in coral reef health

The overfishing of reef sharks such as these is endangering the coral reefs that depend on them. Photo Willy Volk/Flickr

The overfishing of reef sharks such as these is endangering the coral reefs that depend on them. Photo Willy Volk/Flickr

A team from the University of Western Australia has completed a four-month research expedition looking for signs of healthy coral reefs in the remote Kimberley. They observed an unexpectedly high number of sharks in the region, suggesting sharks play a key role in regulating the health of coral reefs.

The study also aimed to assess how marine reserves contributed to the protection of healthy shark populations and reefs.

Based onboard the motor yacht Pangaea, the researchers from the School of Biological Sciences and the UWA Oceans Institute used baited cameras to create video-based observations of reef sharks and fish to assess their abundance and behaviour.

They also used catch-and- release fly-fishing methods to sample fish, measuring their condition and taking tissue samples to determine their diet. The team was excited by the discovery of a potential oceanic shark nursery off the Kimberley coast, where high numbers of individuals under 50cm were observed and sampled.

The team will now process the samples to understand how the presence of sharks contributes to the health of coral reefs. They also intend to assess how marine reserves contribute to the protection of healthy shark populations and reefs.

Program leader Professor Jessica Meeuwig said at a time when coral reefs were under significant pressure from overfishing and bleaching, determining how sharks contribute to reef resilience was critical.

Expedition leader Dr Shanta Barley said the patchwork of protected and unprotected zones that comprised the Great Barrier Reef and other reef systems in Australia offered a unique natural experiment to answer questions around the role of these important and declining animals. ‘The expedition builds on previous work with Pangaea in the British Indian Ocean Territory and Cocos (Keeling) Islands.

‘By using the same methods across these regions we can understand Australia’s reefs in the broader context of the Indian and western Pacific oceans.’


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