In lochs where, as is usually the case, the fish can spawn effectively the fish increase so rapidly that there is not a sufficient supply of food, and the result is that the loch is filled with hungry small trout. When it is remembered that it is reckoned that every spawning trout produces 800 to 1000 eggs for every pound of its weight, some idea is obtained of the rapidity with which fish increase. In many lochs Nature intervenes and the enemies of trout—divers, herons, ducks, otters, etc.—keep the numbers down, sometimes to the point of extinction; in other lochs, owing to the severe frosts and other causes, it is only occasionally that the eggs are hatched out.
2. The lock must not be too deep or the trout will not rise or will not rise well.
This, I believe, is the cause of my failure in several of the lochs upon which I have been making experiments. As Mr. Malloch truly says:
“When a loch is more than 12 feet deep the supply of food soon becomes scarce and the trout small, while shallow lochs produce plenty of food, therefore large trout.... In constructing new lochs, one should endeavour to have as much shallow water as possible.... The best depth is from five to nine feet; beyond twelve feet food becomes scarce and trout do not rise well in deep water.”
