THE SALMON FAMILY. 283 



insect-food so great, that the whole of the Salmonidce in- 

 habiting fresh waters are well known to lose rather than 

 gain in weight during that season. 



Change of Paer into Smolts, and first migration 

 to the sea. 



In somewhat more than twelve months from the time of 

 hatching — that is, between the middle of April and the 

 early part of June — about half of the last year's Parr 

 begin to assume the silver coating of scales preparatory to 

 mating their first trip to the sea as Smolts. These silvery 

 scales, which form the distinctive mark of the Smolt 

 £is distinguished from the Parr, are never put on except 

 when the fish is about to migrate ; and without them it 

 will not migrate at all, and cannot exist in salt water, as 

 has been proved by experiment. The change commences 

 by the tail, pectoral, and back-fins acquiring a dusky mar- 

 gin, the whole body of the fish at the same time exhibiting 

 symptoms of a silvery exterior, with increased elegance 

 of form. AVhen confined in ponds, the habits also of 

 the transforming fish undergo a marked alteration. As 

 Parr they show no disposition to congregate, each occupy- 

 ing its own place, and any intruder upon a post already 

 tenanted being instantly and forcibly expelled ; but as soon 

 as the whole brood have completed their travelling costume 

 — an operation usually lasting two or three weeks — they 

 collect in a shoal, and show their desire to escape by 

 scouring over the ponds, leaping and sporting, and gene- 



