122 THE SEA-TROUT 



remarkable extent by the time they are ready to ascend to fresh water. 

 In some districts they are barely more than quarter of a pound in 

 weight, in others they weigh more than a pound, and I think this 

 variation is due rather to the quality of feeding they have formerly 

 experienced in fresh water as fry and parr than to their subsequent 

 feeding in the sea or estuary. Clearly also it may be due, as we have 

 seen, to some fish being in fact older than others. As going to show 

 how extremely small some whitling may be I show (Fig. 39) the 

 scale of one which was caught in the Little Osen, Hoidalsfjord, by 

 Mr. Hutton. It weighed only i ounce. Yet this fish was a shade over 

 three years old. The reader may check the interpretation of this scale 

 from the scale of another Norwegian whitling here shown (Fig. 40). 

 The first of the three years' residence in fresh water in this case is 

 clearly indicated by the rings of growth subsequently acquired being 

 disconform to those of the first year. This fish weighed 4 ounces. I 

 have heard of no Scottish whitling which weighed so little as the 

 Norwegian fish first here noted. 



What instinct is it, one may ask, which induces the whitling to run 

 at all ? The question, I believe, has never been satisfactorily answered. 

 Size alone appears to have very little to do with it, for in the same 

 district those that are late runners are generally, as one would expect, 

 rather larger than the early runners, but many of the last to ascend are 

 extremely small. Nor, apparently, has their condition of nourishment 

 much influence in the matter, for I have seen them ascend while in the 

 poorest condition. Nor can it be that they are following some special 

 prey up the river else that would easily be ascertained. Finally, their 

 ascent cannot be due to the spawning instinct, as it almost certainly is 

 in the case of grilse of salmon, for, as few out of the large numbers of 

 whitling that ascend can be seen spawning, it is ocularly demonstrable 

 that all whitling do not spawn on their first ascent as salmon grilse do. 

 The two cases are hardly parallel, however, for, while some whitling 



