WHITLING 123 



return in the- same year as their descent — within three months in fact — 

 grilse do. not return until they have spent in addition a full autumn, 

 winter and spring in the sea.^ To describe the whitling as the " grilse " 

 of the sea-trout is thus a little misleading. 



I can hazard no more plausible conjecture for the ascent than this, 

 that the sea-trout being of marked estuarial habits, the shoals of young 

 fish count it immaterial for their winter residence whether they range 

 upwards wholly into fresh water, in which to tell the truth they never 

 range very far, or downwards wholly into salt water, or remain hanging 

 about in the brackish water between the two, their preference being 

 determined at any time by the conditions which prevail in regard to 

 temperature and the volume of fresh water, perhaps, that affects these 

 conditions. It may also be, as Mr. Calderwood surmised, that the 

 younger fish in this matter simply follow the leadership of the maturer 

 shoals which are running up about the same time. It is seldom that 

 the whitling run anywhere in numbers until the Lammas floods have 

 broken. 



Another question now presents itself. Do all the whitling of any 

 year so ascend to fresh water? I cannot believe that they do. I have 

 already suggested that from the time of hatching the tendency of the 

 young sea-trout is to remain together in shoal formation and that they 

 so remain together in the estuary. I would now carry this further and 

 suggest that the shoal still retains its identity in ascending the river, 

 but no longer the shoal in its entirety. Part only ascend, I think, and 

 part remain behind. 



' It has been proved to demonstration by Mr. Calderwood, who in 

 this matter confirms the views of Mr. H. W. Johnston, that the salmon 

 smolts which descend in any particular year do not return all together 

 to spawn as grilse, but that only a proportion does so, the rest remaining 



1. There are a few isolated instances of salmon returnint; to fresh water in the same year as 

 their desciSnt as smolts. Cf. Fishery Board for Scotland— Fisheries, Scotland, Salmon Fish., 1914, 

 III. and IV. (April, 1915). 



