Scientists pose as cleaner fish to perform whale shark ultrasounds
The underwater ultrasounds allowed scientists to capture images of the whale sharks’ internal organs and evaluate their reproductive health.
Freediving scientists were able to position whale sharks for ultrasounds after first removing the copepods – shrimp-like parasites – from their lips and fins.
“When we started to scrape the copepods off their lips, the whale sharks slowed down, hung vertically in the water and treated us like giant cleaner fish,” said lead researcher on the project Dr Mark Meekan, from the University of Western Australia’s Oceans Institute.
Freediving scientists then swam beneath the sharks and scanned their organs using ultrasound.
“It was both an awesome and challenging experience because the whale shark is the largest fish in the ocean, and I was able to watch a live screen view of a beating heart while holding my breath underwater,” said Kim Brooks, the Australian Institute of Marine Science (AIMS) senior field technician who operated the handheld ultrasound.
The resultant imaging revealed whale sharks have a slow heart rate of 12–16 beats per minute. Scientists were also interested in studying the whale shark’s oil-filled liver, which keeps it buoyant.
“We also imaged the back of the shark and could clearly see the skin thickness and muscle bundles,” Mark said.
“It has a layer of hard denticles at the skin surface that feels rough like sandpaper, and below that is connective tissue up to 20cm deep, making its skin one of the thickest of any animal. We found that whale sharks that were skinny and in poor condition had thinner skins.”
The research, published in Frontiers, was led by AIMS in collaboration with The University of Western Australia in Perth and Mira Mar Veterinary Hospital in Albany, as well as international partners.
