206 The Life Story of the Fish 



TUNA 



The tuna is a giant relative of the common mackerel. The 

 name is used for several species, but the one which is of most 

 interest to sportsmen is Thunnus thynnusy the blue-fin tuna. 

 This animal has the less frigid regions of the whole world 

 for its home. In the North Sea, the North Atlantic, the 

 Mediterranean, the Caribbean, the North and South Pacific, 

 and off Madagascar, the same species has been caught. Its 

 relations with man go back into antiquity, for its pictures 

 figure in Greek designs. In spite of all this, very little is 

 known about it. However, to avoid giving a wrong impres- 

 sion, let me specify that it is its life history that is little 

 known. Its insides — its anatomy, its physiology, its chemistry 

 —have been well explored j it is the habits of the beast which 

 remain in darkness. 



Tuna are believed to mature at three years of age, when 

 they weigh about thirty pounds. Spawning presumably oc- 

 curs between December and July, varying with the locality j 

 spawning areas are not definitely known. Eggs, of the pelagic 

 or floating type, have been found in the Mediterranean. 

 They hatch in two days into larvae less than one-quarter inch 

 long. Larvae have been found in the Mediterranean and in 

 mid-Atlantic. Fish under six to ten pounds are unknown on 

 the shores of North America. Large tuna feed on mackerel, 

 herring, dogfish, squid, flying fish. On account of their size 

 and speed, they have only one effective enemy, Orca, the 

 killer-whale, which they greatly fear. 



Migrations northward in summer and southward in win- 

 ter are characteristic of the tuna. In California it makes its 

 appearance off the southern coast in May and moves north- 

 ward as the season advances. In December it vanishes, and 

 from December to May its whereabouts is unknown. It 

 reaches a weight of five hundred pounds and is subject to 



