Young Dolly Varden have about eight to ten wide, dark parr marks or oval blotches which contrast with the mottled olive-brown color of their body. The sea-run fish are silvery with an olive-green to brown color on the dorsal surface and numerous red to orange spots on their sides. The mature males become brilliant red on the lower body surface and the lower fins become reddish-black with white along the leading edges. Mature females are similar but are less brightly colored. Males develop an extended lower jaw which hooks upward, fitting into a groove which is formed in the upper jaw. A hook also forms in the females but is considerably less developed.