A STUDY ON TROUT AND YOUNG SALMON. 



contents of the yolk-sack, become fry and during summer ra- 

 pidly grow. 



How quickly this fry of the year grows in our rivers I am 

 unable to state, my researches only encompassing the trout from 

 the stage when leaving the river and migrating into the salt 

 water. As shown in table V the size of the young trout, when 

 leaving our rivers for the first time, varies between 10 and 

 20 cms., average about 15 cms. 



The age of these emigrating young trout I do not pre- 

 cisely know; but counting the age of the fish from the moment 

 of hatching, they must be at least 1^/4 years old, and conse- 

 quently have spent one spring, one summer and one winter in 

 the river. However, I am inclined to believe that they may be 

 one year older. 



This is only conjecture, and I must expressly state, that 

 I have not acquired material for an indépendant and definite 

 opinion on the matter. As will be noticed my tables only com- 

 prise fish down to 10 cm. length. 



In the tables V, VI and VII the size of trout caught during 

 my investigations is graphically represented. 



These tables comprise a great number of the fishes caught. 

 However they are founded mainly on larger catches, made in 

 single localities during a short space of time. Poorer catches 

 made during a longer space of time, over a large area, I have 

 not used as material for these tables. 



If we look at the groups in Tab. V, we observe that two 

 groups of sizes may be distinguished in the 2 first columns of 

 the table, one group between 10 and 20 cm,, the other between 

 20 and some 30 cm. The fishes constituting the groups are the 

 fishes taken in nearly all the hauls made in the lower parts 

 and mainly in the mouths of the Orkla and the Gula, during 

 May and the first days of June 1898. 



Both these groups represent fish emigrating from the rivers 

 during these months. As I propose to show, later on, the groups 



