1902 Some Signs of Age and Sex in Fishes 183 



than the cod and plaice famihes, on which primarily he has 

 based his doctrine. If eventually we are able to tell the 

 approximate, or even exact, age of a fish by reading off 

 the annual rings in its scales as viewed under a low-power 

 microscope, just as, in somewhat different fashion, the ring 

 marks betray the age of a tree, a very interesting addition 

 will have been made to our practical natural history. Their 

 growth, he thinks, is accelerated in the warm months and 

 retarded in a corresponding degree in the cold, and we may 

 interpret this irregular development at different periods of 

 the year as a proof that abundance of nourishment and a 

 high temperature are coincident beneficial conditions, lack 

 of food likewise accompanying a fall in the thermometer. 



Now, the outward signs of the age of fishes are far more 

 vaguely understood than those which indicate their sex, and 

 it will be the object of the present notes to give some idea 

 of what we know of each outside of the more elaborate 

 intimacy of the scientific laboratory. 



The chief commonly accepted physical index of age in a 

 fish is without doubt its size. There is no nice scale on 

 which size and age are reckoned. Anglers somewhat 

 loosely term a young pike a "jack," though on the Thames 

 and some other waters the word "jack" is used indiscrim- 

 inately of pike of any size. In the same way, the sea-fisher- 

 man calls his young bream either ballards or, at a still 

 smaller stage, chad ; and in Australia the small red bream 

 becomes a " squire " when half grown and a schnapper in 

 its largest stage. 



Such inexact designations are, however, of little scientific 

 value, and must be regarded as having their chief use in 

 the fishing trade, where it is required to indicate fish of a 

 " class," ^ otherwise of a certain size. 



Somewhat more satisfactory are the names applied in its 

 various stages to the salmon, for they indicate the different 

 journeyings of the fish in its strange division of life between 

 salt and fresh water. Thus salmon " fry " grow to a length 

 of perhaps \\ inch at two months, while the "parr" of be- 

 tween 3 and 4 inches is approximately six months old. The 



1 This commercial term must, of course, not be confused with the "class" of 

 zoolo2;ists. Fishes are a class, as also birds or mammals. 



