The brown trout (Salmo trutta) is an originally European species of salmonid fish. The brown trout is normally considered to be native to Europe. Cover or structure is important to trout, and they are more likely to be found near submerged rocks & logs, undercut banks, and overhanging vegetation. Structure provides protection from predators, bright sunlight, and higher water temperatures. Access to deep water for protection in winter freezes, or fast water for protection from low oxygen levels in summer are also ideal. Trout are more often found in heavy and strong currents. The brown trout is a medium-sized fish, growing to 20 kg or more and a length of about 100 cm in some localities, although in many smaller rivers, a mature weight of 1 kg (2 lb) or less is common.