30 The Life Story of the Fish 



seeming to indicate that they grew in one jump to the size 

 of the scale which they replaced, and that only after they 

 had reached the size of the other scales did they begin to 

 trace the record with growth-rings. 



What the fisheries worker needs is large numbers of speci- 

 mens, to enable him to discard uncertain cases, and to average 

 out inaccuracies, errors, and exceptional cases. It is for this 

 reason that the method of calculating past lengths of fish 

 from their scales is especially valuable to him. From a hun- 

 dred three-year-old specimens he can get not only the lengths 

 of a hundred three-year fish, but the lengths of a hundred 

 two-year fish, and of a hundred one-year fish, as well. Using 

 scale-readings, he can construct the life-history of a species 

 with far fewer specimens than he could in any other way. 



It would seem obvious that the fish-fancier's aquarium- 

 dwellers would show no records on their scales. Conditions 

 of temperature and food remain practically constant, and in 

 most of the favorite species spawning is either continuous, 

 once maturity is reached, or very irregular. None of the 

 scales which I have examined, although showing the usual 

 growth-increment rings, are readable. It is possible that the 

 same species in their natural haunts would produce annual 

 checks, for some of the marine tropical fishes in their native 

 waters seem to show them, although there are no well-known 

 seasonal differences in their feeding or other conditions to 

 account for such checks. 



COLOR 



Most people admit that fish are beautiful, but with a note 

 of reservation in their voices — an unexpressed "but." This 

 reservation, it may be hazarded, has to do with the fact that 

 the beauty of fish is purely one of esthetic design, and is lack- 

 ing in the emotional quality which plays an important part 

 in our appreciation of such beauty as that of dogs, horses. 



