SKIMMING THE SURFACE 



of places to deposit their spawn. But the tunny is found 

 in all warm seas. It is one of the largest fishes of the 

 mackerel family, sometimes attaining a length often feet 

 and a weight of a thousand pounds. 



Tuna-fishing — the tunny of the Pacific coast bearing 

 the specific name of ''tuna" — has been a fashionable 

 sport for many years oflf the coasts of southern California 

 and elsewhere, but fishing for tunny has actually been 

 carried on since the days of the Phoenicians. Immense 

 numbers have been caught through the centuries off the 

 Spanish coast and in the Sea of Marmora, but in recent 

 years the main areas of tunny-fishing have moved else- 

 where, to the north coast of Sicily and other places. 



The tunny had the honour, over one hundred years 

 ago, of being the fish which led John Davy (brother of the 

 eminent Sir Humphrey Davy) to a discovery which pro- 

 vided an exception to the time-honoured division of all 

 vertebrate animals into warm-blooded and cold-blooded. 

 John Davy examined the tunny and found that its blood- 

 temperature could be considerably higher than that of 

 the surrounding water. Until then it was assumed that 

 all fish were cold-blooded. 



The variations and movements of tunny and albacores 

 were given royal attention when King Carlos of Portugal 

 ( 1 889-1 908) studied the fish for many years, and finally 

 wrote and published a compendious monograph on the 

 subject, illustrated by remarkable charts and figures : a 

 study of the king of surface fishes by a monarch who was 

 anything but superficial in his researches. His political 

 activities were not so successful as his labours in natural 

 history. With his eldest son, Louis, he was assassinated 

 in the streets of Lisbon. 



It is an amazing fact regarding many surface fishes that 

 the energy which drives even the largest of them (and 

 even the energy which empowers that monstrous mam- 

 mal the baleen whale) comes mainly from planktonic 

 food, most of which consists of tiny organisms. 



47 



