252 FLY FISHING AND SPINNING 



The scales cover the body like the tiles on the roof of 

 a house, and the markings on the exposed posterior portion 

 of each scale may thus suffer. The markings on the 

 anterior and greater portion of the scale surfaces are 

 protected by the overlapping of those above them, and are 

 only affected by physiological conditions such as those 

 which take place as the genital changes occur. The change 

 during this period in the character of the material of 

 which the mucous covering of the scale is formed, may to a 

 certain extent cause the breaking down of a portion of the 

 structure of each scale. 



Prior to spawning, the calcareous or other elements 

 giving this brilliant iridescent sheen to a portion of the 

 membranous covering of the scale, are possibly required to 

 build up the ova of the fish, and as a consequence the 

 appearance of the scales suffers, and this membranous 

 covering loses its brilliancy and resiliency, becoming dull, 

 heavy and coloured. 



As the spawning condition of the salmon approaches, 

 the constituents of the mucous matter appear to alter ; 

 though it does not seem to decrease in volume, it apparently 

 becomes more slimy in character and envelops the scales 

 more thickly especially in the cock fish and gradually 

 merges them more or less into the epidermis. 



SCALE GROWTH 



As the smolt passes into the grilse stage and then into 

 that of the salmon, a series of laminae are being continually 

 added to the scales, the outer edges of which laminae are 

 formed presumably to protect the skin as the body of the 

 fish increases in size and outgrows the covering afforded 

 by the former growth of scale surface. 



The posterior portions of each addition to the scale 

 appear to grow with less rapidity than the anterior 



