A STUDY ON TROUT AND YOUNG SALMON. 279 



the second last column of the table (Table No. IV), correspond 

 in all respects to the emigrants of spring (vide 1st column of 

 the same table). The same facts were also observed at Forve, 

 in the lower reaches of the river and at the river mouth which 

 is subject to the tides and alternately possesses fresh and 

 brackish water. 



From these experiments it transpires, that the young salmon 

 during growth migrate down the river, and during migration 

 gradually acquire the coat of colours peculiar to them when 

 finally leaving the river. 



During all summer there is a constant migration of young 

 salmon down the rivers and into the ocean. 



This migration commences in the rivers Gula and Orkla in 

 May and ceases in autumn because the young in the river then 

 practically cease growing. Thus, as my fishing experiments 

 show, I have during late autumn (October) found the mouths of 

 both these rivers devoid of young salmon. 



When May or spring time has been considered as the 

 annual time of migration, this view is probably derived from 

 the fact that the spring floods quite mechanically convey large 

 numbers of young salmon down the rivers. 



It is of course very difficult to judge at which time of the 

 emigration period, the number of emigrants is largest. However 

 I have the impression that May and June in our rivers, are the 

 months when most young salmon may be caught in the river 

 mouths. During these two months the large floods of the Gula 

 and Orkla generally occur, and this fact would afford sufficient 

 explanation. 



I mention with regret that the material collected by me for 

 illustrating the age of these young salmon is not as large as 

 I should have wished it to be. In order correctly to determine 

 their age, very large numbers of individuals are wanted, and 

 catching the smallest stages in the stony reaches of the rivers 



