Salmonidae

Salmonidae is a family of ray-finned fishes in the order Salmoniformes that includes many species commonly referred to as salmon or trout. The family comprises several genera, notably Salmo (including Atlantic salmon and brown trout), Oncorhynchus (Pacific salmon and rainbow trout), Salvelinus (chars such as Arctic char and brook trout), Coregonus (whitefishes), and Thymallus (graylings). These groups are united by shared features typical of cold-water fishes, including a generally small, adipose fin and a body adapted to life in cool, well-oxygenated waters.

Salmonids inhabit cool freshwater and coastal marine environments across the Northern Hemisphere, with major populations in North America, Europe, and northern Asia. Their ecology is diverse: many species are anadromous, living in the sea and returning to freshwater rivers and streams to spawn, while others are resident in freshwater for their entire lives. They typically move through complex river systems during spawning migrations, and most species exhibit homing behavior to their natal spawning grounds.

Lifecycle and reproduction involve eggs deposited in gravel nests (redds) in streams, which hatch into alevins and later develop into fry and parr. Some species undergo smoltification, a physiological change that prepares juveniles for the transition from freshwater to marine environments. Spawning marks are usually episodic and linked to seasonal conditions.

Salmonids are economically and culturally important, supporting commercial and recreational fisheries and aquaculture. They face threats from habitat loss, barriers to migration such as dams, overfishing, pollution, and climate change, which can alter water temperatures and river connectivity. Conservation efforts focus on habitat restoration, sustainable management of fisheries, and maintaining migratory corridors.