Assessing welfare in wild fish populations requires different approaches than captive settings, with indicators spanning predation risk, parasite burden, habitat quality, and physiological stress markers.
Wild fish welfare is the least-addressed frontier in applied animal welfare science. The sheer scale of wild fish populations — billions of individual animals — combined with the difficulty of welfare assessment in aquatic environments has historically placed wild fish welfare beyond the scope of practical concern. This is changing. New non-invasive monitoring techniques, growing recognition of fish sentience, and the clear role of human activities in causing preventable fish suffering are driving a nascent wild fish welfare field. Key human-caused welfare impacts — sea lice spillover from fish farms, thermal stress from climate change, habitat degradation — are addressable through policy and management interventions. Wild fish welfare deserves the same moral consideration as other animals in human-influenced environments.