Migratory fish including salmon, sea trout, shad, and lamprey face multiple welfare challenges along their migration routes from freshwater to marine environments and back.
Migratory fish welfare is shaped by the quality of the entire migration corridor - from spawning rivers through estuaries and coastal seas to ocean feeding grounds. Barriers at any point in this corridor impose welfare costs: the energetic cost of attempting passage, injuries from failed attempts, and failure to reach spawning habitat. Pollution in estuaries and coastal waters imposes physiological stress during critical transition periods between fresh and salt water. Ocean changes from climate and fishing pressure affect growth and survival in marine phases. The welfare of each migratory fish depends on conditions across multiple countries and habitats simultaneously.