Rising water temperatures, altered precipitation patterns, and changing ocean chemistry from climate change are disrupting migratory fish runs with welfare implications for billions of individuals across threatened species.
Climate change creates welfare harms for migratory fish through thermal stress, altered energy budgets, and ecological mismatch. Fish experiencing temperatures above their thermal tolerance show accelerated physiological stress responses, immune suppression, and increased pathogen susceptibility before lethal temperatures are reached. Mass mortality events - thousands of fish dying in river reaches that have become lethal heat traps - represent welfare harm at scale. The gradual nature of climate change means these welfare impacts are cumulative and worsening. Adaptation measures including cold-water releases from stratified reservoirs, riparian shade restoration, and strategic dam operations provide partial welfare relief in already-impacted systems.