Rare basking shark with a head for science becomes model specimen

16/07/2015

You wouldn't know it to look at him but this shark is model material. Sure, he's not what you'd call classically good looking – his eyes are small and his teeth far from impressive. But he's a basking shark. And southern hemisphere scientists don't see many of them.

A fortnight after his untimely death in the nets of a fishing trawler off Portland, the head of the male basking shark has been removed and made its way to Melbourne where it has been scanned so Museum Victoria can make a 3D model for public display.

"This is the first time we have done 3D scanning at the museum, certainly at this scale," said Martin Gomon, the museum's senior curator of ichthyology.

At 6.5-metres long, the shark was too large to transport and store whole. So along with the 600-kilogram head, Museum Victoria researchers removed the 2.6-tonne animal's dorsal, pectoral, anal and pelvic fins and a selection of vertebrae ranging in size from a dinner plate to a saucer. Muscle and tissue samples were also taken for DNA and isotope analysis.

Scanning the head took some preparation. After being frozen on a timber pallet in a walk-in freezer, it took three days for the head to defrost enough for preparatory staff to open the jaw. By the fourth day, the cavernous mouth could be opened wide enough for metal poles to pass through to the back of the animal's throat. Only then could the male shark be hoisted up by chains attached to an overhead gantry in the museum's loading dock.

Still dripping as it thawed and smelling distinctly fishy, 3D scanning engineer Ben Tam from scanning company Qubic got to work.

Waving a scanner resembling a high-tech iron, Mr Tam recorded in 3D detail the colour and shape of the head, including the folds of the gills and inside the creature's cavernous mouth.

Capturing information between 10 and 15 frames a second, the scanner generated up to 15 gigabytes of raw data.

The information will be used to 3D print a replica basking shark head to go on public display at the museum.

The computer model, which will be able to be manipulated by researchers for viewing from all angles, will become a tool for future study.

The fins have had moulds made so that replicas can be produced using fine dental plaster.

Now soaking in a tank of 10 per cent formalin solution, the fins will be kept as a resource for researchers to refer to later.

"We can compare their morphology with fish from other areas to see if they are a different species or how they are related to other species," Dr Gomon said. "The internal structures can also be X-rayed or CAT-scanned, so they are very valuable."

The head, having been injected with a preservative, will also be stored in a large tank of 10 per cent formalin solution.

The second biggest fish after whale sharks, basking sharks are rarely found in Australian waters because they live well off the continental shelf.

Globally, basking sharks are listed as vulnerable on the IUCN Red List.

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