Hatchery salmon interacting with wild populations can affect wild fish welfare and population genetics in complex ways.
Competition between hatchery and wild salmon affects the welfare of wild fish through reduced access to food and optimal habitat during critical periods. Wild salmon experiencing higher competition stress have elevated cortisol levels and reduced growth and survival. Interbreeding between hatchery and wild fish produces offspring with reduced fitness - a form of welfare harm extending across generations. The perpetuation of fishing pressure on declining wild populations through hatchery supplementation prioritizes human use over the welfare and recovery of wild fish. Hatchery reform that genuinely supports wild population recovery rather than substituting for it is the more welfare-consistent approach.