Distribution: Northern Hemisphere, but widely introduced in cold waters for sports and aquaculture. Many are anadromous, spending part of their life at sea, but returning to freshwater where all species spawn in a gravel bed in rivers or streams; most fish die after spawning. Small cycloid scales. Gill membranes reaching far forward, detached from isthmus. Axillary process on pelvics. Last three vertebrae directed upward. No spines. Adipose fin present. Attains 1.5 m (maybe 2 m) maximum length. Highly valuable in sport and commercial fisheries. There is disagreement about the status of some species and genera.