The eggs are adhesive for a short period after extrusion which allows those not lodged in gravel from being washed away. The number of eggs produced by a female varies with her size. After spawning is completed the female covers the eggs with gravel in a similar manner as when she constructed the redd. A four year old brook trout inhabiting a perpetually cold spring brook may be only six inches in length and weigh only an ounce or so. However, a brook trout of the same age inhabiting a relatively rich lake habitat may be as much as four pounds.
Brook trout are a relatively short-lived fish.
Age studies throughout North America have demonstrated that brook trout more than three or four years of age are relatively rare. Individuals as old as seven years old are occasionally taken, but two and three year old fish make up the bulk of anglers catches. Maturity is not related to size. Young and medium sized trout eat large numbers of aquatic insect larvae and terrestrial insects. During the cold months they rely on insect larvae found on the bottom.