When hatching begins, the water in the trough is raised, and the trays are brought near the surface and held there by light wedges which do not spring the sides of the troughs. The feather sweeps the bottom of sediment, taking care not to injure the delicate embryos, for they are more delicate when first hatched than when in the egg. At this time cleaning should be confined to the removal of any dead eggs or fry and of egg-shells on the screen, and here is where the little flat net of milliner's "millinet," on a three-inch brass-wire frame, is found most useful. This wire is covered with muslin to which the netting is sewed, and, moved quickly through the water, it gathers the shells which are clogging the screen, and a smart rap on a pan cleans the net. It is also of use in taking out dead fry and foreign matter from the bottom, as well as deformed fish, for we find crooked-tailed fish that can not swim and take food, double-headed fish, and twins attached to one sac, which never live.
When first hatched the embryo trout hardly look like fish; they have simply burst the shell in which they appeared as a slim, dark body, with big eyes, coiled around the yolk, and now merely straighten out and have the great yolk-sac still attached, and so heavy that they can not swim, but lie on their sides and huddle together to avoid light; and now there is danger of the bottom ones being smothered. Cover the trough in spots to induce them to gather in different places, and keep them as dark as possible. At this stage there is nothing to do but to remove the few dead sediment can not hurt them now—and keep the outlet screen free. When they get to be about a month old the sac will be nearly gone, and the fry begin to show signs of swimming by occasional darts from the bottom to examine some floating particle. They will take food some days before the sac is absorbed, and it should be offered to them in small quantities.
The best food that I have found is beef liver, after abandoning it for soft clams (Mya arenaria) salt-water mussels, and horse meat. The clams made the young fish grow fast, but did not produce the expected number of eggs; the mussels were tried raw and cooked, with the same result; and, as the principal object at this State hatchery was the production of fry for planting public waters, we. next tried raw horse flesh, which was very objectionable on account of the large proportion which was passed undigested and clogged the screens and fouled the water. Several fish culturists have found an admixture of bran, shorts, or mill feed with liver to be excellent. This I have not tried, because the trout is not a vegetarian in the least degree, and it remains to be proved that such vegetable addition to the food is of real advantage.
The liver is fed raw; for the "babies" it is run through a
