ON SALMON. 



43 



feeding and growing, and until it greatly surpasses in weight its contem- 

 porary in the river. 



And if such a fish spawns and survives to regain salt water, a long time 

 must elapse before it can recover merely the weight it has lost in the river 

 and until it can begin to increase in size over its original weight, when it 

 first left the sea for the act of spawning. Consequently it can never reach 

 the normal weight for maiden fish of corresponding age. 



The whole of the material in my tables shows the same conditions, and 

 I have merely selected the above as a characteristic example. 



' (d.) The Relative Occurrence of the Different Age-Classes in Different 



Localities. 



It has long been known that the salmon of the north and those of 

 the south for example, from the neighbourhood of Trondhjem or of 

 Christiansand are different in size. In the north they are considerably 

 larger than in the south. v 



Herr Landmark has proved this by a large number of measurements, 

 and in my investigations, with the help of several firms, I have collected 

 a quantity of material which clearly proves the correctness of this theory. 



In a number of the icehouses where fish are bought there exist statistics 

 spread over many years giving the total catch and weight of grilse (fish 

 under 3 kilos) and of salmon (fish of 3 kilos and over) which have passed 

 through each fish-house. 



I have collected the statistics which I have obtained from the Christian- 

 sand and Trondhjem districts, together with those of the fish caught with 

 rod in the State-owned rivers in Einmarken. (See table below.) 



The table shows us two facts. In the first place the quantity of grilse 

 in proportion to salmon decreases as we proceed northwards. Secondly, 

 the average size of both grilse and salmon increases the farther north we 

 go. This is especially the case with salmon. 



