Tiny reef fish inspire submarine designers

June 18th, 2008 - 2:29 pm ICT by IANS  

Sydney, June 18 (IANS) The wing-like fins of tiny reef fish allow them to cruise at the human equivalent of 60 km per hour and also negotiate strong currents with ease. Their prowess has now drawn the attention of the US Navy, whose submarine designers are studying what makes these fish so fast.

The researchers found the reef fish could move at up to 10 body lengths per second, while Olympic champions reach speeds of just 1.3 body lengths per second, and then only for the brief 22 seconds of the 50-metre freestyle sprint.

“Some species of parrotfish, wrasse and surgeonfish have developed wing-like fins which they move in a flapping motion, just like a bird,” said Chris Fulton of the Australian National University who led a study of the reef fish.

“This allows them to generate high swimming speeds with relatively little energy so they can move easily around their turbulent, wave-swept habitats.

“Reef fish just 10 cm long can cruise all day at an average speed of 3.6 km per hour, which is the equivalent of a typical person swimming at more than 60 km per hour.”

Understandably, the design of the fins has drawn the attention of underwater submersible designers and the US Office of Naval Research.

“While we are seeing rapid advancements in submersible design … we are yet to match the speed and efficiency achieved by these wing-finned coral reef fishes,” Fulton said. “We still have much to learn from over 50 million years of reef fish evolution.

“We were surveying fish populations on the Great Barrier Reef in 2000 and realised some of them had these unusual, wing-like fins. When we looked on coral reefs in Tahiti and the Caribbean, we found more ‘winged’ fishes.

“We discovered that the fastest reef fishes have tapered fins, which they tend to flap in a figure-of-eight sweep that creates thrust on every stroke,” Fulton explained.

“Some of these fish play a crucial role in maintaining the health of our reefs by eating the fleshy algae that would otherwise overgrow and smother live corals,” Fulton said.

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