After this process is done both the male and female can find another fish to spawn with. When hatched, the sac fry will remain in the gravel until all of their yolk is absorbed. They become free swimming when they reach about 1.5 inches long. The scales begin to form when the young are about 2 inches long. Brook trout are considered to be carnivorous, they will eat anything their gape can accomodate.
Young brooks eat large amounts of aquatic insect larvae.
The larger, mature brooks will eat insects, fish, molluscs, small mammals and even snakes. The trout will also cannibalize their own eggs and young in the spring. Predation of brook trout also occurs by birds such as the Kingfisher and the Merganser. Parsitism of brook trout is a common occurance. The main parasites are Trematodes, Cestodes, Nematodes, Microsporidian parasites and Flukes.