of the Salmon in Fresh Water. 159 



15. THE PIGMENTS OP THE MUSCLE AND OVARY OF 

 OP THE SALMON AND THEIR EXCHANGES. 



BY M. I. NEWBIGLN, B.Sc. 



Among the many curious and interesting changes which the salmon 

 undergoes throughout the year, not the least interesting is the variation 

 in colour seen in the skin, the muscle, and the ovaries. 



When the fish comes from the sea the skin is of a clear, bright 

 silvery hue, while the flesh has the familiar strong pink colour. The 

 small ovaries are of a yellow-brown colour. As the reproductive organs 

 develop during the passage up the river, certain definite colour changes 

 occur. The skin loses its bright silvery colour, and, more especially in 

 the male, acquires a ruddy-brown hue. At the same time the flesh 

 becomes paler and paler, and in the female the rapidly growing ovaries 

 acquire a fine orange-red colour. The testes in the male remain a 

 creamy white. 



After spawning the skin tends in both sexes to lose its ruddy colour, 

 and to regain the bright silvery tint ; the flesh, however, remains pale 

 until the kelt has revisited the sea. In other words, the salmon comes 

 from the sea with a store of pigment in the muscles. During its 

 sojourn in the river this pigment disappears from the muscles, is appar- 

 ently in the female for the most part transferred to the ovaries, and so 

 to the ova, and in both sexes is to a smaller extent deposited in the 

 skin, there to undergo f urther changes. The accumulation of pigment 

 in the muscle is associated with the presence of a large amount of fat, 

 and fat and pigment disappear pari passu. 



While in the Salmonidse this colour change is most marked in the 

 salmon, it is also observable in the sea trout. Even in certain varieties 

 of brown trout, e.g. the Loch Leven trout, the pigmentation of the flesh 

 is well marked when the fish are in prime condition, and becomes less 

 marked as the genitalia develop. In all cases there seems to be the 

 same close association between fat and pigment, and the simultaneous 

 disappearance of the two. 



Even outside the limits of the family of the Salmonidse, pigmentation 

 of the flesh is known to occur. Thus the Dawson salmon of the 

 Australians ( Osteoi/lossum leichardti), a member of a small tropical 

 family, is described as having pink-coloured flesh,\vhich tastes like that 

 of the English salmon. The flesh of the Australian mud-fish (Ceratodus 

 forsteri), again, is described as being oily and of a dark red or pink 

 colour. Although there is no direct evidence, the descriptions would 

 lead one to believe that in these cases also the pigment is associated 

 with the presence of fat in the muscle. 



As the pigments in these and other cases have been directly ascribed 



