Fig. 377. Adult Salmon.
The genus Salmo includes three species, namely, Salmo salar, S. croix, and S. trutta, the trout. Of these, S. salar (Fig. 377) has the body long, the muzzle roundish, but more so in the male than in the female, the upper jaw provided with a fossette, into which the point of the lower jaw penetrates; the back is a slaty blue, the sides and lower part of the body of a silvery diaphanous white, with great black spots scattered round the upper part of the head, round the upper edge of the eye, and over the operculum or covering. Some brownish irregular spots, variable both in form and size, are sprinkled over the sides. In other respects their colours are subject to variations according to circumstances. Before assuming the characters here indicated, however, the salmon has passed through three stages, each of which is marked by peculiarities worthy of being noted. The young salmon (Fig. 378) is greyish and striped with black. At the end of a year it has acquired a fine metallic hue. "The other parts," according to Mr. Blanchard, "are of a dazzling steel-blue; eight or ten large spots of the same brilliant blue cover it as with a silvery mantle on the sides; between these spots a reddish, or, rather, brightish-rusty iron colour prevails; a black spot is usually observable in the middle of the operculum. The belly is of a fine diaphanous blue in the parr" (Fig. 379).
Fig. 378. The Young Salmon.
Dr. Bertram gives a very clear and intelligible account of the early days of the salmon, which was at one time veiled in mystery. "The spawn, deposited by the parent fish in October, November, and December, lies in the river till about April or May, when it quickens into life. I have already described the changes apparent in the salmon's egg, from the time of its fructification till the birth of the fish. The infant fry are of course very helpless, and are seldom seen during the first week or two of their existence, when they carry about with them, as a provision for food, a portion of the egg from whence they emanated. At that time the fish is about half an inch in size, and presents such a singular appearance that no person seeing it would ever believe that it would grow into a fine grilse or salmon. About fifty days is required for the animal to assume the shape of a perfect fish; before that time it might be taken for anything else than a young salmon. At the end of two years it has changed into a smolt. After absorbing its umbilical bag, which it takes a period of twenty to forty days to accomplish, the young salmon may be seen about its birthplace, timid and weak, hiding about the stones, and always apparently of the same colour as the surroundings of its sheltering place. The transverse bars of the parr, however, speedily become apparent, and the fish begins to grow with considerable rapidity, especially if it is to be a twelvemonth smolt, and this is very speedily seen at such a place as the Stormontfield ponds. The young fish continue to grow for a little more than two years before the whole number make the change from parr to smolt, and seek the salt water. Half the number of any one hatching begin to change at a little over twelve months from the date of their coming to life. And thus there is the extraordinary anomaly of fish of the same hatching being at one and the same time parr of half an ounce in weight, and grilse weighing four pounds. The smolts of the first year return from the sea, while their brothers and sisters are timidly disporting in the breeding shallows of the upper streams." A late sea-going smolt explains the anomaly of a spring salmon.
Fig. 379. Salmon, or Parr, a year old.
It thus appears that, in its first stage, the Young Salmon (Fig. 378) is called a parr: during the second it is a smolt, namely, a parr plus a jacket of silvery scales. While they continue in the state of parr they lead a secluded life, totally unable to endure salt water, which would kill them. When they have become smolts the fish betake themselves in bands to the sea. The sea-feeding being favourable, and the fish strong enough for the salt water, a rapid growth is the consequence. After that they disappear, spreading themselves over the wide world of the ocean. At the end of two months of a life mysterious and so far unknown, these fishes reappear in the rivers, returning to their native pools; but how changed! Quantum mutati! The smolt, which has lived in the river two or three years, and only attained the length of six or eight inches, returns at the end of two months' sojourn in the sea, weighing three to four, and after six months, ten or twelve pounds. It is now a grilse.
After depositing their eggs the grilse remain some time in the fresh water, when they again go to the sea. This second sojourn, of about two months, is sufficient to send it back weighing from six to twelve pounds. It is now an adult salmon. Each new visit to the sea brings the salmon back increased in size in proportion to the duration of the voyage. In the month of March, 1845, the Duke of Athole took a salmon in the Tay after it had deposited its eggs; he marked it by attaching a metal label to it. It weighed ten pounds. The same individual with its metal label was again fished up after five weeks and three days' absence. It now weighed twenty-one pounds, having in the meantime travelled forty miles down the river to the sea. This fish must, however, have made a long sea run during these thirty-eight days and its seeking up the river again.
In most circumstances, according to Mr. Blanchard, to whom we are indebted for much information relative to the development and migration of these fishes, salmon of various ages, which have nevertheless sojourned in the sea as grilse, adult salmon, and others intermediate between them, whose first sojourn at sea has extended to eight or ten months, ascend the rivers together in an order no less varied, the older individuals heading the column, the youngest bringing up the rear.