It would be an interesting study were we to trace the stages through which the young fish becomes evolved from its simple germ, and the wondrous formation of tissues and organs out of the soft jelly-like matter of which the egg is primarily composed. But want of space forbids; and our readers must therefore fancy for themselves the process whereby the hidden artist Nature works through development, and at length shapes out the young salmon, or ‘parr.’ It may be mentioned in proof of the small proportion borne by the salmon-eggs actually deposited, to those developed, that authorities agree in stating that out of three thousand eggs deposited, scarcely _one_ egg may survive—so terrible is the destruction of young salmon. This fact alone, as Mr Young argues, should tell powerfully as an argument in favour of _artificial_ propagation; since out of three thousand eggs which are thus hatched, at least one thousand young fishes may be successfully reared.
The curious fact is noticed that in most if not all broods of salmon, half of the parrs will become ‘smolts’—as they are called in their next stage—at the end of a year or so, whilst the other half will not become smolts _until after the lapse of two years and more_. This incongruity, if we may so term it, has led to the questions, ‘Do the parrs become smolts between thirteen and fifteen months after they have left the egg, or at the age of two years and two months?’ Both questions may apparently be answered in the affirmative, since each brood exhibits this peculiar feature of some of its members coming to the smolt-stage long before the others. Mr Young remarks on the authority of a salmon-breeder in the north, that about eight per cent. of the salmon hatched by this gentleman became smolts at the end of the first year; about sixty per cent. at the end of the second year; and about thirty-two per cent. at the end of the third year. These facts would seem to indicate that the end of the second year is the most natural period for the assumption of the smolt-guise, which, as distinguished from that of the parr, exhibits a beautiful coat of silvery mail.
The parr, it may be remarked, dies if placed in sea-water, whereas the smolt thrives in the latter element. On reaching the sea, the young smolt may measure from four to five inches. After a residence in the sea of some six or eight weeks, the smolt returns to its river as a ‘grilse,’ which varies from five to eight or nine pounds in weight, according to the time it has remained in the sea. After returning to its river the grilse spawns, and then returns to the sea. The features of the mature salmon are now apparent, and the fish increases in size after each such annual migration to the sea. Indeed nothing is more extraordinary in the history of the salmon than its rapid increase and growth after these periodical migrations to salt water. Three salmon which weighed ten, eleven and a half, and twelve and a half pounds as they were migrating seawards, were duly marked; and on being caught six months afterwards when returning to the fresh water, were found to have increased in weight to the extent of seventeen, eighteen, and nineteen pounds respectively. Although salmon usually return to the rivers in which they first saw the light, yet it has been ascertained that the practice is not an invariable one. There is no good reason why one river should not suit a salmon as well as another, and in their wide migrations these fishes are exceedingly likely to enter rivers other than their native streams.