“They don’t have to,” replied Earl. “Salmon have a peculiarity which makes it easy for the hatchery people. When spawning time comes, salmon always return to the place where they were born. The young ones gradually work their way down to the sea and go out into the ocean. Just where they go, no one knows, but after a period of three to five years they come back up the streams in swarms. They never mistake the streams, but always come up the one which they went down years before. The Fishery Department has determined this by tagging the salmon and then catching the same ones years afterwards.”