River restoration projects that remove barriers, restore floodplains, and improve water quality have direct welfare benefits for wild fish populations.
Individual wild fish welfare is directly affected by river condition. Barriers that prevent migration force fish to repeatedly attempt impassable obstacles, causing exhaustion and injury. Thermally degraded river sections create stress for cold-water species during summer heat events. Poor water quality from agricultural runoff reduces oxygen availability and increases disease. River restoration directly improves welfare for individual fish by enabling migration, providing thermal refugia, improving food availability, and reducing disease pressure. The welfare benefits of restoration scale with the number of fish occupying improved habitat.