THE IMPENETRABLE SEA 



several pounds in weight and is known as a grilse. From 

 that stage onwards, and until the time comes when the 

 salmon feels the urge to fight its way up-stream through 

 the same river, it may or may not voyage out into the 

 ocean wastes. Some certainly travel enormous distances. 

 As recently as the autumn of 1955, a salmon tagged in 

 Ross-shire eleven months earlier was recaptured off the 

 coast of Greenland, having travelled 1,700 miles. This 

 incident is regarded as one which affords an important 

 clue to the problem — nevertheless the habits of the fish 

 while it passes through the salt-water stage of its amazing 

 existence still constitute one of the sea's most baffling 

 mysteries. 



The salmon's leaps over rapids may seem to be a kind 

 of flight, but they are not flying fishes in any sense — their 

 mighty jumps are empowered by initial propulsive efforts 

 through the water, and not by any motion of their fins as 

 wings. 



But some fishes have appendages closely resembling 

 wings, and use them with extreme rapidity as they travel 

 through the air, although they manipulate them to main- 

 tain height rather than to propel themselves forward. 

 Most flying fishes glide, rather than fly with ''wing" 

 motions. Frank W. Lane, in his Nature Parade, "^ describes 

 how a flying-fish "flies". He says that the fish uses its 

 abnormally large pectoral fins as supporting surfaces, 

 while its initial impulse, which empowers the entire flight 

 after it has caused the fish to leave the water, comes from 

 a rapid "sculling movement" of the lower lobe of the 

 caudal fin or tail. He gives the underwater speed as 

 only thirty-five miles an hour, but this speed is fast 

 compared with a shrimp's "speed" — a mile in four 

 hours. Swimming creatures of the sea vary amazingly in 

 their rates of progression. Between the lazy crawl through 

 water of the shrimp and the flying-fish's flashing leap lie 

 the bream's mile and a quarter an hour and the four 



♦Jarrolds (London) Ltd., 1946. 



38 



