IT may be a dog-eat-dog world, but the willingness of great hammerhead sharks to eat their cousins has helped illuminate the species' 'crucial' role in the food chain.
A University of Newcastle study carried out in conjunction with Macquarie University is the first of its kind to determine where large adult great hammerhead sharks stand in coastal food chains.
Marine ecologists discovered the animals are apex predators in the coastal ecosystem because they devour other sharks and rays as a specialty.
Lead researcher Dr Vincent Raoult said he was hopeful declining shark populations could be better protected thanks to the research, having dropped 90 per cent over five decades.
"What our research has found is that the great hammerhead shark is in fact the 'shark predator', it confirms that they are at the top of the food chain and highlights that their role in our coastal ecosystem is absolutely crucial," Dr Raoult said.
"Apex predators keep the balance of our ecosystem in check, they keep it healthy, so this discovery about the great hammerhead really emphasises its importance.
"Until now the role of these sharks in the food webs of coastal ecosystems has been poorly understood."
Researchers studied stable isotopes of samples of muscle, liver and vertebrae from hammerheads caught as bycatch off the Australian east coast.
It helped them discover that hammerheads over three metres feed primarily on whaler sharks and stingrays, shifting them into the top spot across multiple food webs in the area.
Reaching up to 4.5 metres, the great hammerhead shark is the largest variety. They use their unique head or cephalofoil and exceptionally large dorsal fin to pursue specific prey.
While it makes them adept at hunting their quarry, their specificity also makes the creatures more susceptible to extinction.
Great hammerheads are listed as vulnerable in NSW. Demand for their fins and commercial fishing have been factors in their decline alongside shark net programs including drumlines and gillnets.
A SMART drumline trial ran across Stockton, Nobbys, Newcastle, Bar Beach, Dixon Park and Merewether beaches from February 1 to April 30 this year.
Dr Raoult said the findings of the study, published in the Journal of Fish Biology, should lead to better protections.
"Now that our study has shown just how important their role is in linking coastal food webs, it is absolutely crucial that we see urgent conservation of the species," Dr Raoult said.
"As apex predators, their extinction would have a vast ecological impact on the coastal ecosystem and protection is essential to support stability across economically important ecosystems."
The research was funded by a Sea World Research and Rescue Foundation grant and the NSW Department of Primary Industries.