Freshwater fish migration is blocked by millions of barriers globally, causing individual welfare costs through exhaustion, injury, and reproductive failure that parallel the conservation impacts of population decline.
Fish migration barriers impose welfare costs on individual fish in addition to the well-documented conservation impacts on populations. Fish that encounter impassable barriers do not simply turn around and find alternative habitat — they persist in trying to ascend, exhausting themselves over days or weeks, sustaining injuries from turbulent water, and dying without spawning after investing the enormous energetic cost of beginning migration. This individual-level suffering adds moral urgency to the conservation case for barrier removal and fish pass installation. The welfare-positive interventions are identical to the conservation-positive ones: remove barriers where possible, install effective fish passes where removal is not feasible, and ensure culverts are designed for fish passage. Welfare biology provides an additional reason to prioritise these investments beyond ecological metrics.