340 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 193 3 



The distance covered by the initial taxi is usually about 5 to 15 

 meters (or yards) ; some taxis are at least 20 meters long, but the 

 average is nearly 50 times the length of an average flying fish, or 

 about 9 meters (30 feet) long. Numerous timings made by me in 

 Asia indicate that the average time involved in covering this distance 

 is about 0.9 second. The average speed for the surface period of 

 movement is therefore about 10 meters per second (36 kilometers 

 per hour). This is the speed of an athlete on a short dash. But the 

 speed of the fish, since it is accelerated during the taxi, is probably 

 greater at the end of the taxi, when the fish hurls itself into the air. 

 On the basis of some field observations (degree of detail not indi- 

 cated) and of aerodynamic computations, Shoulejkin (1929) has 

 concluded that a speed of 16 to 18 meters per second is attained at 

 the end of the taxi. Like an airplane, the fish probably increases 

 its power as it approaches the take-off. 



To attain this speed the sculling action of the caudal fin must 

 be very strong and rapid. My observations indicate an average of 

 about 50 to 70 complete or double vibrations per second and 5 to 7 

 vibrations per meter. 



The biplane flying fishes very often prolong their flight by taking 

 a new start. Since they expend no energy to increase or maintain 

 their speed in the air they gradually settle down to the water. They 

 then either dive into the water or again start violently sculling to 

 initiate another long leap through the air. The taxis of a compound 

 flight subsequent to the initial taxi are typically short, seldom 

 lasting a second and probably averaging half a second. 



THE ACTUAL FLIGHT 



During both the initial and intermediate taxiings the pelvic fins 

 must remain folded tightly against the belly, for at these times they 

 are alwaj^s invisible. But at the instant the fish leaves the surface 

 these fins flash into clear view and are very easily seen with binocu- 

 lars or even with the unaided eye, especially when the pelvics are 

 blackish. It is assuredly the upward force of air pressure on these 

 posterior planes that lifts the drooping tail out of the water and thus 

 actually initiates the air flight proper (fig. Id). When the fish is 

 thus forced into a horizontal position it lies at most only a few centi- 

 meters above the sea. This is probably a main reason why many 

 flights are abortive, ending almost at once in a steep little wave. 



The often repeated claims that a flying fish sustains itself in the 

 air by flapping or rapidly vibrating the pectoral " wings " are ap- 

 parently due, as already stated, to preconceived ideas that fishes must 

 fly like birds, or to uncritical deductions that the mechanics of flight 

 demand such movement, or to untrained or inattentive observation. 



