ON TROUT. 



67 



in November it is warmer than in June. These circumstances "would lead 

 one to imagine that we have here the cause of the late start in growth of 

 the trout in this lake. 



2. TROUT FEOM OTHER LAKES. 



The material which I have obtained from other lakes and streams 

 consists in the first place of some large samples from different localities. 

 From these I have .been able to compile comparative figures of the relative 

 size in relation to age. 



I have, further, a series of smaller but carefully selected samples, which 

 have been treated according to the methods of investigation and measure- 

 ment described on pages 23 and 25, and the values thus obtained enable one 

 to estimate the average lengths which the fish at the place in question 

 usually attains on the completion of its first, second, third, etc., winter of 

 existence. 



The values we get in this way, as I have described at length on the 

 pages referred to, are sufficiently exact for purposes of comparison. 



Let us first consider three large samples which are respectively from 

 Krokaa, Chaigijok above Easti Lombola, and from Sandvand.* 



Samples from these waters have been dealt with in Tables XXXIII. , 

 XXXIIlB., XXXIV. and XXXV., from which we obtain the following: 



Here we see that in all the samples we get relatively few of the 

 youngest year-classes, principally because they are too small to take a hook ; 

 and, again, another noteworthy point is that the numbers increase with age, 

 to decrease once more as they approach the maximum age. This decrease 



* Sandvand on the mainland, a little south-east of Harstad, is a lake about one 

 kilometer in length and 500 metres wide at its broadest part. It lies at a slight elevation 

 above the sea, though sea fish are unable to get right up to it. 



Krokaa is a small river or rather a large burn which flows through a mountain valley 

 into Skilbotten at Bronnoy in Sondre Helgoland. A high perpendicular waterfall about 

 100 metres from the sea prevents sea trout from ascending it. 



Chaigijok. The main source of Ovre Laksvand, Lakselv, Finmarken. Easti Lombola 

 is a lake-like expansion in the lower sluggish portion of Chaigijok. 



52 



