10 September 2010

NEWS FROM THE FOREFRONT OF FLYING FISH SCIENCE
























(Photo from here.)

I'm not sure I know of anything more enjoyable than cruising a warm ocean, feet dangling off the bow of a sailboat, peering down as flying fish power along underwater and then erupt into the air to glide, digging their tails into the surface and kicking off when they need another few seconds of flight before diving back underwater.

(Photo from here.)

Flying fish are masters of the elusive. And not just masters of eluding predatory fish. After searching for images for this post, I realized how few and far between are the quality photographs of flying fish.

Even legendary BBC film crews, lavished with time, money, and equipment, brought back only ho-hum footage of flying fish for the recent LIFE series. (I tried to embed the LIFE clip but couldn't.) It was a good clip, of course, it's goodness magnified, as always, by Attenborough's wheezily wondrous narration and a lyrical score. 

But having spent an awful lot of time watching flying fish in the wild, I can say it's not nearly as good as the real thing. And that's not always the case. Many times documentary footage of wild animals is better than you ever experience with your eyes, since cameras are essentially bionic extensions of our eyes, able to zoom close or record in slow-motion or decipher great detail in low light. 


Sailfish Drama from Howard Hall on Vimeo.

A good example of the power of cameras can be seen in this gorgeous video shot by my old friends Howard and Michele Hall of sailfish herding what might be flying fish, though maybe not, since they don't seem to fly. Still, it's mesmerizing. Particularly the eye-opening shots from underwater of frigatebirds feeding at the surface.













Elusive or not, I did find this small image of a fossil flying fish. Seems poignant to me, somehow, a fish flying through time. 

But the poignance was lost on whomever posted the image on this website:

The ‘flying’ fish Exocoetoides minor, fossilized in Lebanese Cretaceous rock. This rock is alleged by evolutionists to be around 100 million years old. The fossils indicate that flying fish have always been flying fish.

Of course, flying fish have always been flying fish. Before that they were, in all likelihood, regular flightless fish.
























Or were they?

There does not seem to have been a whole lot of scientific study of flying fish. So I was interested to see this new paper today, Aerodynamic characteristics of flying fish in gliding flight, in the Journal of Experimental Biology. Here's the abstract:

The flying fish (family Exocoetidae) is an exceptional marine flying vertebrate, utilizing the advantages of moving in two different media, i.e. swimming in water and flying in air. Despite some physical limitations by moving in both water and air, the flying fish has evolved to have good aerodynamic designs (such as the hypertrophied fins and cylindrical body with a ventrally flattened surface) for proficient gliding flight. Hence, the morphological and behavioral adaptations of flying fish to aerial locomotion have attracted great interest from various fields including biology and aerodynamics. Several aspects of the flight of flying fish have been determined or conjectured from previous field observations and measurements of morphometric parameters. However, the detailed measurement of wing performance associated with its morphometry for identifying the characteristics of flight in flying fish has not been performed yet. Therefore, in the present study, we directly measure the aerodynamic forces and moment on darkedged-wing flying fish (Cypselurus hiraii) models and correlated them with morphological characteristics of wing (fin). The model configurations considered are: (1) both the pectoral and pelvic fins spread out, (2) only the pectoral fins spread with the pelvic fins folded, and (3) both fins folded. The role of the pelvic fins was found to increase the lift force and lift-to-drag ratio, which is confirmed by the jet-like flow structure existing between the pectoral and pelvic fins. With both the pectoral and pelvic fins spread, the longitudinal static stability is also more enhanced than that with the pelvic fins folded. For cases 1 and 2, the lift-to-drag ratio was maximum at attack angles of around 0 deg, where the attack angle is the angle between the longitudinal body axis and the flying direction. The lift coefficient is largest at attack angles around 30~35 deg, at which the flying fish is observed to emerge from the sea surface. From glide polar, we find that the gliding performance of flying fish is comparable to those of bird wings such as the hawk, petrel and wood duck. However, the induced drag by strong wing-tip vortices is one of the dominant drag components. Finally, we examine ground effect on the aerodynamic forces of the gliding flying fish and find that the flying fish achieves the reduction of drag and increase of lift-to-drag ratio by flying close to the sea surface.

In other words, flying fish glide as well as birds. Other fun flying fish facts:

  • Flying fish can remain airborne for more than 40 seconds
  • They can cover distances of up to 400 meters/1,300 feet at speeds of 70 kph/43.5 mph
  • By gliding near the surface of the sea, they glide farther


But if you dig a little deeper into this paper you come to realize that these researchers figured out the flight performance of flying fish by flying dead stuffed fish in a wind tunnel. Some were stuffed and flown with fins extended. One was stuffed and flown with fins held back against the body.

I began to feel a little like the victim of a dead parrot skit

Oh well, flying fish are elusive even to the grasp of modern science. May they be so for another 10,000 x 10,000 years.
























Flying fish. 1910. Herbert James Draper. From here.
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