will get them in
their youth to adopt the habit of feeding freely at the surface. When
the alders and willows have grown sufficiently and are well covered with
leaves, they will probably give enough shelter to the fish to make the
boards at the upper end of the pond unnecessary.

As time goes on, and the little fish grow, they should be thinned out,
the smaller and weaker being removed into another pond. Despite the best
endeavours of the fish culturist, a certain number of these small fish
are sure to keep to the lower end of the pond, and it is these which
should be removed first. If they are left, the difference in size
between the smaller and the larger will soon become so great that the
large fish will very likely be tempted to eat the small ones, thus
developing a cannibalistic habit which they will keep always.

At the end of August or the beginning of September the little fish will
have got over the most dangerous part of their lives. After this time
they are called yearlings, are much more hardy and not subject to nearly
as many risks as up to that time.

The great points to remember are:--That the food should be varied as
much as possible; and as much natural food, of a hard description such
as shrimps, _corixae_, snails, bivalves, etc., be given. That the little
fish should be well protected from enemies. That they should not be
over-crowded, but the weakly and small fish be separated from the larger
fish. That frequent doses of earth should be given to keep the bottom
sweet and clean.[2] That the inlets and outlets should be frequently
cleaned and kept clear, to ensure a good flow of water through the
ponds, and that a careful watch should be kept for such misfortunes as
fungus and dead fish, in order that they may be dealt with at once.

[2] See two letters in Appendix.--Page 93

CHAPTER IX

TROUT. THE FRIENDS AND ENEMIES OF THE FISH CULTURIST

The creatures which are sometimes found in and around rearing ponds
containing ova or young fish are very numerous, and it is advisable that
the fish culturist should have some knowledge of them. It is for this
reason, that while I cautioned my readers against the creatures which
are dangerous, and enumerated some of those most serviceable as food, I
left detailed descriptions of these enemies and friends of the little
fish, in order that I might deal with them in a separate chapter.

[Illustration: LARVA OF _DYTISCUS_ AND YOUNG TROUT.]

Among the w