io6 THE SEA-TROUT 



such very imperfect data as I possess bearing upon the point — imperfect 

 as bemg gathered m a restricted field. But my data, so far as they go, 

 suggest speculations which seem to me to be reasonable, though not a 

 little surprising, and all the more interesting that they once more bring 

 us into touch with the theory that there is only one species of trout in 

 the British Isles. 



I think, then, that it is very improbable that any young sea-trout will 

 in its hrst year — that is, during the year in which it is a "sea-trout fry" — 

 descend to the estuary or the sea, nor is proof of such a descent any- 

 where to be found. 



It is quite possible, however, in such rivers as the Tay, the Tweed 

 and the Leven, where the tidal influence is felt for a considerable 

 distance above the actual mouths of the rivers, and in waters such as 

 are found in the Orkneys and the Hebrides, which are hardly distin- 

 guishable as salt or fresh, that some of the young fish may, in their 

 second year — that is, as " sea-trout parr " — drop down towards salt 

 water though never adventuring, as true " sea-trout smolts," that year 

 into water which is markedly salt. Mr. Calderwood, in one passage 

 in " The Life of the Salmon," makes a suggestive remark in this 

 connection besides incidentally showing that he has some belief in the 

 " shoal theory," which I have already propounded. As to some small 

 salmon fry being found near salt water in the lower reaches of the Tay 

 he hazards this explanation : — " It seems probable, however, that other 

 young fry, following the instinct to form into shoals which we know 

 parr possess, have joined themselves to companies of larger parr, or it 

 may be have been to some extent washed down by floods." Much 

 more is this descent probable in the case of the sea-trout, a more 

 characteristically estuarial fish than the salmon ; but here again I can 

 give no proof of such a descent in the second year. 



The earliest marked descent of the sea-trout smolt occurs in its 

 third year, that is, after it has spent two winters in fresh water After 



