Anadromy

Anadromy is a migratory life history in which fish grow and mature at sea, then enter freshwater to reproduce. It is a form of diadromy, migration between marine and freshwater habitats.

Smoltification: A developmental transformation that prepares juvenile salmonids for life in seawater. It equips young salmon and trout for the seaward phase before their return migration.
Atlantic salmon: A salmon species native to the North Atlantic and its connected rivers. It feeds and matures at sea, then returns to freshwater rivers to spawn.
Catadromy: A migratory life history in which fish grow in freshwater and move to sea to spawn. It reverses anadromy’s direction of migration for reproduction.
Fish ladder: A structure that helps fish pass a barrier by moving through a sequence of pools or steps. It can reconnect spawning habitat upstream of dams on anadromous migration routes.
Marine-derived nutrients: Nutrients transported from the ocean into terrestrial or freshwater ecosystems by organisms and materials. Spawning anadromous fish carry ocean-acquired nutrients into rivers and surrounding landscapes.
Osmoregulation: The regulation of water and dissolved ions across an organism’s body. Anadromous fish must adjust ion and water balance when crossing between seawater and freshwater.
Chinook salmon: The largest Pacific salmon species, native to the North Pacific and its river systems. Its long ocean growth and freshwater spawning exemplify anadromy in Pacific salmon.
Amphidromy: A life history involving movement between freshwater and the sea that is not primarily for breeding. Unlike anadromous fish, amphidromous fish use both habitats for growth rather than migrating to sea to mature.
Fish passage: The movement of fish past obstacles such as dams, weirs, and culverts. Maintaining passage in both directions is necessary for anadromous migrations.
Salmon run: The seasonal mass migration of salmon from the ocean into freshwater spawning grounds. Large runs create concentrated pulses of food and nutrients in river ecosystems.

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