The average life span of a rainbow trout is six years. Its average weight is one pound in streams and five pounds in Lake Michigan and the average length is 10 to 15 inches. The back of this fish is olive green, the sides are silvery with a pink stripe and the belly is silvery. Spots are present on the back, dorsal fin and caudal fin. The tail is forked. The adipose fin has a black edge.
The rainbow trout lives in Lake Michigan and is stocked in many lakes and streams. This fish reaches maturity at age three. Spawning occurs in spring. The female deposits 500 to 9,000 eggs which are buried in gravel. Eggs hatch in 30 to 100 days. The rainbow trout eats insects, snails and small fishes. The rainbow trout is exotic to Illinois. Native to the Pacific coast of North America, the rainbow trout is widely stocked throughout Illinois.