The European eel is critically endangered, with populations at 5% of historical levels, and individuals face welfare challenges across their extraordinary life cycle.
European eel welfare is affected by parasitism, hydroelectric turbine mortality, and river barrier obstruction across their extraordinarily long life cycle spanning decades. Anguillicola crassus infection impairs the swim bladder function eels require for deep-ocean migration, causing many to fail to complete their breeding migration. Turbine passage kills significant proportions of downstream migrants. Individual eels that survive decades of freshwater residence to begin the breeding migration face accumulating injuries and welfare challenges. Eel passes, bypass channels, and turbine screens reduce individual welfare harm from migratory obstacles.