Flying fish ‘perform as well as some birds’

WASHINGTON - Flying fish can stay airborne just as well as small-to-midsize birds, according to a new study.

Haecheon Choi, a mechanical engineer from Seoul National University, Korea, became fascinated by flying fish when reading a science book to his children.

Realising that flying fish really do fly, he and his colleague, Hyungmin Park, decided to find out how these unexpected fliers stay aloft and publish their discovery that flying fish glide as well as birds on 10 September 2010 in The Journal of Experimental Biology.

But getting hold of flying fish to test in a wind tunnel turned out to be easier said than done. After travelling to Japan to try to buy fish from the world famous Tsukiji fish market, the duo eventually struck up a collaboration with the National Federation of Fisheries Cooperatives of Korea.

Park went fishing in the East Korean Sea, successfully landing 40 darkedged-wing flying fish. Selecting five similarly sized fish, Park took them to the Korean Research Centre of Maritime Animals, where they were dried and stuffed, some with their fins extended (as in flight) and one with its fins held back against the body, ready to test their aerodynamics in the wind tunnel.

Park and Choi measured the forces on the flying fish’s fins and body as they simulated flights.

Calculating the flying fish’s lift-to-drag ratios - a measure of the horizontal distance travelled relative to the descent in height during a glide - Choi and Park found that the flying fish performed remarkably well: gliding better than insects and as well as birds such as petrels and wood ducks.

And when they analysed how the fish’s lift-to-drag ratio changed as they varied the tilt angle, the duo found that the ratio was highest and the fish glided furthest when they were parallel to the surface, which is exactly what they do above the ocean.

Measuring the airborne fish’s pitching moment, the duo also found that the fish were very stable as they glided.

However, when they analysed the stability of the fish with its fins swept back in the swimming position it was unstable, which is exactly what you need for aquatic manoeuvrability. So flying fish are superbly adapted for life in both environments. (ANI)