It is difficult to lay down any certain rule as to what is the best time at which to take the next step--that of turning the fry out into the rearing ponds. When the fry have got into more or less regular habits, and showing no fear of whoever it is who feeds them, come up readily and seize the food boldly, is probably the best time to let them out into the larger space of the pond. I do not mean to say that when a certain proportion of the fish have got over their natural shyness, and feed boldly and without hesitation, the whole of them should be set free. What I mean is, that when the habit of associating the appearance of a certain individual with a meal has been well established among them for a week or so, they should be allowed to escape from the box into the pond.
This is best done in the same way that the alevins were allowed to escape from the hatching tray into the box--by lowering the level of the box so that its upper edges are some two or three inches below the surface of the water. The food should now be thrown into the pond higher up, so that the little fish may be induced to swim up and station themselves as near the inlet as possible. Probably some of the little fish will not leave the box at all of their own free will. These, of course, will have to be turned out. The box should not, however, be lifted out of the water and the fish and water together be poured out, as this is very likely to cause them severe injury. The box should be gradually tilted over and lifted out of the water bottom first, so that the fish are hardly disturbed at all and certainly not injured in any way.
An important matter to consider before turning the little fish out into the pond is, how the ponds are to be protected so that their many enemies may be kept away from the fry. Kingfishers, herons, and other creatures are very partial to young trout and will cause enormous destruction if not prevented. Kingfishers have, in my experience, been the worst offenders. Some years ago I was rearing some trout in a part of the country where many of the inhabitants bewailed the extermination of the kingfisher. Before I began rearing trout I agreed with these people, for a kingfisher flitting along a stream looking like a little mass of jewels is a pleasing sight, and one which I had never enjoyed in that particular part of the country.