THE AGE OF FISHES 197 



pounds, and offer a spectacular challenge to anglers who 

 gather for the famous Tuna Tournaments at Bimini and at 

 the fabulous Cat Cay Club. School after school of these fish 

 pass by for two weeks or more, steadily driving northward in 

 the current as if following a definite timetable. Later they are 

 found off the coast of New England, where they feed on 

 herring and mackerel. Finally in August they congregate in 

 large numbers off Wedgeport, Nova Scotia, where they grow 

 fat on the abundant food fish, and where competitors in the 

 International Tuna Competition pit their skill and the strength 

 of their rods and lines against the sheer weight of a fish that 

 has been known to reach 1,800 pounds. 



Schools of tuna have been seen off Jamaica during Febru- 

 ary, and isolated fish have been seen at other parts of the 

 Caribbean Sea. It is probable then that they begin their long 

 journey somewhere in this part of the West Indies, but just 

 where they start and what path they take we do not know. Nor 

 do we know when they breed, though their roe appears to be 

 spent when they pass through the Florida Straits. Above all, 

 we do not know what happens when they disappear from 

 Nova Scotia. Perhaps the investigations now being carried 

 out from Miami and Bermuda and Woods Hole will bring 

 the answer. 



Many of these journeyings — and those of other fish we have 

 not mentioned — are in some way triggered into action by the 

 breeding urge or by an urge to seek distant feeding grounds. 

 The fishes themselves are undoubtedly guided in some man- 

 ner by ocean currents, by changes in temperature and saltness, 

 by the amount of oxygen or carbon dioxide in the water, or by 

 the direction of sunlight. Just how these complex influences 

 play their part has never been completely explained for any 

 fish migration. The American bluefin tuna migrate along the 

 slowly cooling length of the Gulf Stream, but since the tem- 

 perature changes only by an infinitesimal fraction of a degree 

 for each mile or so of the course there is nothing along the line 



