How young salmon in freshwater habitats experience welfare challenges and what factors determine pre-smolt survival and quality.
Pre-smolt salmon welfare in freshwater is shaped by the quality of the river ecosystem they inhabit. Adequate flow, appropriate water temperature, diverse invertebrate food sources and territorial space for young fish are all welfare determinants that are directly influenced by catchment management, climate and water quality. The welfare harm of drought-driven low flow and high water temperature is both an acute mortality event and a prolonged welfare stress for fish that survive - thermal stress, reduced oxygen availability and intensified competition for increasingly scarce cool refugia all represent welfare costs. River restoration that improves these conditions improves the welfare of every fish in the system.