Innovative imaging of whale sharks
An international team of researchers has discovered a new method of imaging free-swimming whale sharks using underwater ultrasound.
The research, published in Frontiers, was led by the Australian Institute of Marine Science (AIMS) in a collaboration with The University of Western Australia, WA’s Mira Mar Veterinary Hospital, Okinawa Churaumi Aquarium in Japan, and Georgia Aquarium in the US.
Lead author Dr Mark Meekan, from UWA’s Oceans Institute, has been running a monitoring program at WA’s Ningaloo Reef with AIMS for the past 20 years.
“Whale sharks are large filter feeders which makes them vulnerable to consuming plastics and man-made chemicals in the water, so we want to know if they’re healthy,” Dr Meekan said.
As part of the program the researchers have been collecting tiny parasites called copepods, a small shrimp-like animal, from the whale sharks’ lips and edges of their fins.
“We found when we started to scrape the copepods off their lips, the whale sharks slowed down, hung vertically in the water and treated us like a giant cleaner fish,” Dr Meekan said.
While the whale sharks were in this position the researchers were able to use an underwater ultrasound to capture images of the internal organs to help to assess their condition and reproductive status.
Kim Brooks was AIMS’ senior field technician during the expedition and operated the hand-held ultrasound unit while free diving with a dozen whale sharks.
“We began by trying to find landmarks inside the body, starting with the heart and from there tried to work out where we were in relation to the rest of the organs,” Mr Brooks said.
“It was both an awesome and challenging experience because whale sharks are the largest fish in the ocean, and I was able to watch a live screen view of their beating heart while holding my breath underwater.”