On the question of food supply it is worth while to recall the words of Mr. F. H. Halford:[34] “Food supply generally is ... chiefly dependent on the presence of the weeds in which the best forms of food for the fish are to be found.... It must not, however, be forgotten that, in Marryat’s terse words, ‘while floating food is caviare, sunk or mid-water food is beef to the fish.’ Hence, when engaged in his examination of the weeds and the animal life contained therein, the fisherman should remember that he can only expect well-fed, good-conditioned, healthy, and consequently game trout in a (loch) which contains a bountiful supply of crustaceans, such as fresh-water shrimps and mollusks such as snails of the genera _Limnaea_, _Planorbis_,” etc., etc. Further, it is of the utmost importance that the number of fish in the loch should be regulated in such a way that the food supply may be sufficient to enable the fish to grow to a large size. Where the fish cannot spawn effectively, and it is therefore necessary to renew the stock, experience alone can decide the number of fish which should be put into the loch every year. Spring is the best time to do this. The number of fish which should be put in will obviously depend chiefly upon the amount of food in the loch and the number of fish caught, and destroyed by their enemies, during the preceding year. In many lochs there are stones under which the small trout can find protection from the large ones, but where there is no protection it is worth while to put stones or small drain tiles round the edge of the loch. 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.” [Illustration: (Deep Water)] [Illustration: (The Loch Shore)] XVI