Digital mischief - Isobel Rodgers.
Digital mischief - Isobel Rodgers.

Divers don't let grey nurse sharks get a good day's sleep

TOO MANY curious divers in one place could disturb the sacred slumber of the gentle grey nurse shark, a Southern Cross University scientist has discovered.

PhD graduate Mateus Baronio has spent five years studying grey nurse and leopard sharks around Julian Rocks with a state-of-the-art remotely operated vehicle (ROV).

The $50,000 machine enabled Dr Baronio to quietly get within centimetres of the fish and observe their breathing habits as they slept.

Unlike most sharks, grey nurse and leopard sharks are able to hover in the same position while resting.

But because they sleep during the day, if too many divers converge on their position, they will stir and move away.

"As soon as the divers leave the area, the sharks go back to sleep, so if you don't have a massive number of divers, the sharks still have enough time to rest," Dr Baronio said.

"(But) if you have too many divers doing the wrong thing, you're going to have an impact on the sharks."

QUIETLY: Mateus Baronio, from SCU Marine Ecology Research Centre, with an ROV.
QUIETLY: Mateus Baronio, from SCU Marine Ecology Research Centre, with an ROV. Patrick Gorbunovs

Divers around Cape Byron Marine Park shouldn't worry - the existing code of conduct and usage of the site is sustainable at current levels. If anything, the local scuba industry has been a boon for the welfare of sharks in the area.

"We think the scuba industry has a huge benefit on shark conservation. They were to the first ones to pick up on the decline in grey nurse populations and their presence puts an economic value on shark numbers," Dr Baronio said.

The real crux of Dr Baronio's thesis was his pioneering use of ROVs for empirical research of shark behaviour.

Unlike a conventional manned dive, the vehicle allows researchers to observe sea life for an unlimited time and, of course, avoids potential confrontations with the more dangerous shark species known to hang around.

Until Dr Baronia's work, ROVs had been used for documentaries, but not for research.

Julian Rocks is considered vital to the endangered grey nurse shark, which may use the dive spot as a waypoint in its migratory pattern, or even for reproduction.



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