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Biophysics

Biophysics

Unusual flying fish twist and turn to soar

05 Jul 2017 Sarah Tesh
Do the twist: ribbon halfbeak fish have a unique method of flight

Scientists have uncovered how ribbon halfbeak fish “fly” despite having no hind wing fins. Yoshinobu Inada from Tokai University in Japan and colleagues have mimicked the fish’s flight, hoping to find the optimal design of tandem wing planes.

To evade predators, “flying fish” have evolved to propel themselves out of water and soar above the surface. Normally, the fish can achieve this short flight because they have two sets of “wings” – large pelvic fins act as horizontal tail wings similar to those toward the rear of planes, and large pectoral fins are used as the standard large wings.

A unique twist

The ribbon halfbeak fish, however, lacks the large pelvic fins. To investigate, Inada and colleagues 3D printed a model resembling the fish. They analysed the effect of wing positions on flight performance using a wind tunnel. “Amazingly, they solve the problem by rotating their rear body by 90°, and use their wide dorsal and anal fins as a horizontal tail wing,” explains Inada. “This is a really unique behaviour.”

In conjunction with their twisting bodies, ribbon halfbeak fish also reduce the effect of downwash on the tail wings by lifting the rear of their body above the pectoral wings. “This has a positive effect on improving the lift and flight performance of the fish,” says Inada.

The researchers believe the fish developed this unusual method of flight because of different evolutionary pressures compared to other flying fish. The work is being presented at the Society for Experimental Biology Annual Main Meeting 2017 taking place in Gothenburg, Sweden.

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