Page:British Reptiles, Amphibians, and Fresh-water Fishes.djvu/82

BRITISH FRESH-WATER FISHES for their fast when they go down to the sea, especially between the stages of Smolt and Grilse, and Grilse and Salmon. Once having reached the sea it is an oceanic wanderer, visiting the North Atlantic and elsewhere, and feeding upon herrings, mackerel, sand-eels, and other fish. The young prey upon fresh-water shrimps, insects, and other aquatic creatures. It is stated that the ova (or eggs) will not develop in salt water, hence the visits of this species to fresh rivers, and it has been proved that it is possible for Salmo salor to pass the whole of its life, from birth to death, in fresh water. The alevins, or fry, are hatched about March, and at first the contents of the yolk-sac, carried on the under part of the body, are sufficient to keep them going, as is also the case with their cousin, the Trout, shown in Fig. 32. After a Kelt has spawned it is in a weak condition, but has perforce to make its way to the sea. It is also subject to more than one disease. Thus weakened, it falls an easy prey to human as well as natural enemies, and many never reach the sea at all. The descent to the sea usually takes place in early Summer, sometimes earlier or later, according to the favourability of the season. It is not possible to enter into detailed descriptions of the appearance of the fish during each stage of its evolution, and it must suffice if reference is made to the beautiful silver coat of the adult Salmon, and the fine pink or red colour of its flesh. This latter is due to the storage of extra oxygen. The record weight for an adult British specimen seems to be 70 pounds, from the River 66