Sharks more abundant on healthy coral reefs

by James Cook University on 14 Sep 2014 A new study by researchers from James Cook University and the Australian Institute of Marine Science has revealed sharks in no-fishing zones in the Great Barrier Reef (GBR) Marine Park are more abundant when the coral is healthy.

The study examined the distribution patterns and habitat associations of sharks, using thousands of baited remote underwater video stations (BRUVS) across the entire GBR Marine Park over a 10-year period from the year 2000.
'This study has demonstrated how important the health of coral reefs is for the future of shark populations on the GBR,' said Mario Espinoza, an AIMS@JCU student and lead author of the study.

'Some shark species that use coral reefs are under pressure from fishing, and maintaining healthy reefs will help populations survive and rebuild,' Mr Espinoza said.

'Our results suggest that healthy reefs make good shark habitat, and may be just as important for improving shark numbers as protecting them from fishing,' Mr Espinoza said.

'So looking after our reefs will have direct benefits for the sharks that live on them.'

Professor Colin Simpfendorfer from JCU’s Centre for Sustainable Tropical Fisheries and Aquaculture, and a co-author of the study, said recently published results from AIMS had shown a 50 per cent decline in coral cover on the GBR since 1985.

'Given the decline in coral cover on the GBR over the past three decades there are likely to have been negative effects on shark populations,' Professor Simpfendorfer said.

The study also demonstrated that since the rezoning of the GBR in 2004 some species of sharks found on coral reefs had increased, he said.

'Grey reef sharks, a species known to have been reduced by fishing in the past, have increased in abundance since more of the reef was protected,' said Dr Michelle Heupel, a co-author of the study and ARC Future Fellow based at AIMS.

'This is a positive sign for this species, and demonstrates the benefit of closing some reefs to fishing.'
The BRUVS used in the study record animals attracted to a bait and enabled scientists to count and identify sharks that occur on the GBR.

'This is a powerful, non-destructive technique that provides a permanent record on film and can be used in any habitat, depth or zone of the GBR,' said Dr Mike Cappo from AIMS, a study collaborator.

'This method has the potential to be a key element of future integrated monitoring of the health and management effectiveness of the GBR World Heritage Area', said Dr Cappo.

The results of this study are helping scientists and reef managers to better understand the role of reef health in assessing the benefits of marine protected areas for sharks.

Funding for the analysis of the BRUVS data was provided by the Australian Government through the Tropical Ecosystem Hub of the National Environmental Research Program.

AIMS@JCU is a joint venture between AIMS and JCU to facilitate the sharing of research infrastructure and provide enhanced opportunities for the training of postgraduate students in tropical marine sciences.

The results of the project have been published in the journal PLOS James Cook University website