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Tiny fish's swimming skill could speed up submarines

Posted on Jan 16, 10:45AM | IANS

Tiny coral reef wrasses swim as fast as some of the fastest fish, but only with half as much energy, which could help revolutionise robot submarine technology, Australian researchers say.

Current Autonomous Underwater Vehicles (AUVs) use propellers or jets at the back. "By replacing these with fins at the front to mimic how the bluelined wrasses flap their fins, we could propel robots with less power, saving on batteries and increasing their range," said Chris Fulton from the ARC Centre of Excellence for Coral Reef Studies and The Australian National University.

"For a long time, people thought the best high-speed swimmers were the fish cruising in open waters, like mackerel and tuna," says Fulton, the journal Public Library of Science ONE reports.

"Our study shows that these coral reef wrasses, by virtue of their unique wing-like fins, can maintain very similar speeds at a dramatically lower energetic cost," Fulton said.

Tuna and mackerel move their bodies and tails to propel themselves through water. While this makes for speed, it can come at a high energetic cost. Bluelined wrasses, however, flap their tapered fins in a figure-eight pattern that produces thrust on every stroke, making it far more energy efficient.

"This figure-eight fin sweep allows the bluelined wrasse to create a lift force as the water flows over their fins, in a very similar way to how birds fly. This means the fish are literally flying underwater," Fulton said.

"Fish use up to half of their energy on swimming. If they can save even just a fraction of this, they can spend it on growing bigger, holding larger territories and producing more offspring," he said.

"Just imagine if you could save 40 percent on the petrol bill for your car, how good would it be to spend that spare cash on other things?" Fulton added.