Sperm is collected from male fish in the same manner and is mixed with the eggs to fertilize them. The fertilized eggs are placed in incubators which resemble chests of drawers where a steady flow of cold, clear water supplies oxygen to the developing embryos. Cutthroat and lake trout eggs take about six to eight weeks to hatch in the 48 degree Fahrenheit water flowing through the incubators. In 21 days, the head and tail have formed. Until the embryo's eyes begin to show, the egg is very delicate and cannot be moved.
Blood vessels collect food for the growing embryo from the energy-rich yolk material.
When the egg is about to hatch, the young fish becomes very active and its wriggling and movements help break the thin shell. Once this is used up, the fry swim off the bottom in search of food. Hatchery trout are fed a specially formulated dry food which, when the fry first begin to feed, is about as fine as table salt. As the young fish grow, the particle size of their diet is increased. We stock them into lakes and streams at sizes ranging from one to eight inches long, depending on the requests of state and federal biologists.