GROWTH OF SALMON AND TROUT. 



73 



CTO 

 100 



two factors of age and growth, that is to say to difference in age and 

 difference in growth; and we have now the advantage of being able to 

 demonstrate in every case, with certain limits, what the difference consists 

 in, and can resolve the variation into its several elements. 



Any attempt to group the different " forms " within definite classifica- 

 tions on the basis of growth, will, in my opinion, at any rate with the 

 insufficient material we possess, be impracticable, owing to the variations 

 in rate of growth which present themselves. 



ak~, 



80 

 70 

 60 

 SO 



to 



ID 

 10 



/i&4-5678<f/0/J JiVratre, 

 FIG. 31. Diagram showing Growth of Salmon and Different Trout.* 



It would therefore appear that so far as our present information goes, 

 we cannot place reliance on anything but the manner of growth. We have 

 seen in all our investigations that the fish grow in two manners. Either 

 they have a regular consistent development, vigorous or poor, throughout 

 the whole of their lives, or else, like salmon, sea-trout, Mj0sen trout, and 

 many other fresh-water trout, they change suddenly from a more or less 

 poor form of growth to a totally distinct and more rapid growth under more 

 favourable conditions of existence. 



* Laks = Salmon, Mjos-orret = Mj0sen trout, Sjo-orret = sea-trout, Fjeld-orret = 

 mountain trout (from Osf jorden), Bak-orret = Burn-trout (from Chaigijok). 



, 



