SALMON DISCOLOUEED BY FEESH WATEE. 201 



longer and larger than those of a salmon of the same 

 size. 



The backs, a great portion of the sides of the 

 gill-cover and of the rays of the fins, of river Shin 

 fish, become nearly black after two or three weeks 

 sojourn in fresh water. The chief cause arises 

 from the colouring matter in that river, which is 

 mainly fed from sources originating in peat soils, 

 or flowing through them. I believe that the 

 Avaters of all rivers, derivable from sources of the 

 character of those of the Shin, speedily discolour 

 or render dark the bright, silvery scales of fish 

 fresh from the sea; and I believe that all fresh 

 water, no matter how pure its source, has a 

 similar effect, though less in degree. A black, 

 or dark fish, therefore, can never be a fresh-run 

 salmon. 



Although a grilse or salmon, fresh run from the 

 sea, is larger and in better condition than it will 

 be after a few weeks' sojourn in fresh water, it is 

 neither so strong nor so active. At all events, its 

 strength and activity are not so enduring. One 

 evident cause of this is, that fresh water hardens 

 and renders tough and stiffly elastic, the fins*, 



* Mr. Shaw remarks, — " On the approach of autumn, 

 the whole of the SalmonidtE, resident as well as migratory, 

 while in fresh water, acquire a dusky exterior, accompa- 



