Fish stocking programs release hatchery-raised fish into rivers and lakes, raising welfare questions about hatchery conditions, release stress, and survival rates of stocked fish.
Fish stocking involves multiple welfare impacts. Hatchery conditions including high stocking density, artificial lighting, and processed food diets impair immune function and natural behavioral development. Transport to release sites causes osmotic stress, temperature variation, and crowding. Release into unfamiliar waters exposes hatchery fish to predators and foraging challenges for which they are unprepared, causing high mortality in the first weeks. Oxygen depletion during transport and crowding causes suffering. The welfare of individual stocked fish is poor by any measure. Conservation stocking of genuinely threatened species under carefully managed programs with good survival outcomes is more defensible than recreational stocking of catchable-sized fish for immediate angling harvest. Pre-release conditioning programs improve survival but require significant investment.