THE SALMON FAMILY 61 



another like the tiles on the roof of a house, the free 

 edge of the scales being towards the tail. The number 

 of scales on any particular fish remains the same through- 

 out life, and as the fish grows in size the scales grow in 

 proportion so as to cover the skin entirely. 



The increase in size of the scales is by the means of 

 rings of growth, which are added round the edges, in 

 a manner similar to the rings of growth seen in the 

 section of the stem of a tree. It is the arrangement of 

 these rings of growth that affords an indication of the 

 age of a fish. During the summer, when the weather 

 is warm and food is plentiful, the fish grows rapidly in 

 size, the scale grows at a proportionate rate, and so each 

 ring of growth is of considerable width. In the winter 

 the growth of the fish is retarded, and so each ring of 

 growth is narrow. 



The outer edge of each ring of growth is marked by 

 a distinct line. The summer growth on a scale is seen 

 as a broad, light crescentic band, in consequence of these 

 lines being far apart, and winter growth is shown as a 

 narrow dark crescentic band, in consequence of these 

 lines being close together. In this way it is possible 

 to read the age of a fish by the arrangement of the rings 

 of growth on its scales. 



Calderwood, Johnson, Hutton, Mallock and others 

 have thoroughly studied the scales of the salmon, and 

 have in this, and in other ways, considerably added to 

 our knowledge of its life history. By the scale markings 

 it is possible to state when the smolt went to sea, how 



