NATURAL HISTORY OF BRITISH SALMONID&. 141 



One half of the young fry migrate when about a year old- 

 almost all the other half at their second year and the few 

 remaining at their third year but the period of the descent is 

 very generally the same in either case and in all rivers, whether 

 early or late beginning in March and continuing through 

 April, May, and the early part of June only a few fish con- 

 tinuing to migrate during the subsequent months. 



The length of the smolt when migrating varies from three 

 and a half to seven or eight inches, according to age and other 

 circumstances. 



Its full colours are, dark blue or bluish green on the upper 

 half of the body and head, with black or carmine coloured 

 ftpots ; gill covers and lower half of the body silvery, and all the 

 fins much darker than those of the parr. The silver scales 

 come off on slight pressure and the parr marks are visible 

 below. What becomes of the young fish after reaching the sea 

 is still, more or less, a matter of conjecture. What we do know 

 positively is, that in from six to eight weeks a number return 

 to the same river with an increase in weight of from two to five 

 pounds, and that many of the fry marked when migrating as 

 smolts in May and June, are sold in the London markets as 

 grilse in July, August, and September. It is a fair point for 

 conjecture, and would be an interesting subject for future ex- 

 periment, whether the grilse returning the same season may 

 not consist principally of the tivo-year-old smolts, and so on ; 

 or whether, should this prove not to be the case, these older 

 smolts may not represent the larger-sized grilse, and the younger 

 fish the smaller ones. 



The following is the actual growth of some smolts marked 

 at Stormontfield, when on their way to the sea, and captured on 

 their return as grilse during the same year : 



Weight 



July i . . .3 Ibs. 

 July 20 . .55 Ibs. 



July 21 . . .5 Ibs. 



Weight 



July 31 . . . 9i Ibs. 

 Aug. 4 . 7i Ibs. 

 Aug. 4 ... 8 Ibs. 



July 30 . . 7^ Ibs. 



Of the habits and food of the salmon in its various stages 



