nd sea-trout is practically the same as
that of the common trout, except that they require more water. If kept
in rearing ponds they grow more quickly than they do when left to find
food for themselves. While young, the salmon is marked with transverse
bars of a darker colour than the rest of the body. During the time it
bears these marks it is known as a parr.[3] In about fifteen months it
loses these marks and becomes quite silvery, being now known as a smolt.
Shortly after assuming the smolt dress, the young salmon takes its
departure to the sea. In some cases the young salmon do not appear to go
down to the sea till over two years after being hatched out, but they
should always be set at liberty in March, April, or May in the year
following that in which they were hatched out, according to how far they
have developed the smolt or silver appearance.

[3] All the trouts go through this stage, which is distinguished by
"finger marks" upon the sides.

If spring water is obtainable, particularly if the water, as is usually
the case, is of an even temperature throughout the year, the troubles of
the fish culturist are considerably lessened. Without a building for the
hatching troughs it is almost impossible in many places to guard against
frost unless such a spring is available. Sediment may be avoided by
putting frames covered with flannel at the inlets to the hatching beds,
these will, if kept clean, prevent any sediment from coming into the
ponds, and will allow plenty of water to flow in. If hatching trays are
not used, the bottom of the artificial bed should be covered with clean
gravel.

The time which elapses from the impregnation of the eggs to their
hatching out varies according to the temperature of the water, a fairly
average time is about ninety days. The ova should be watched during this
time, and the dead ones removed. For a short time after they are
impregnated they are fairly hardy, but from then till shortly before
they hatch out the very slightest concussion will kill or seriously
injure them.

The management of sea-trout ova is similar to that of salmon, and the
ova are obtained in the same way. As in the case of the salmon it is
best to rear the little fish artificially, till they are ready to go
down to the sea; they will thus escape dangers likely to cause the loss
of about eighty per cent. of their number.

The same methods and the same precautions as advised in the chapters on
rearing trout s