River lampreys are ancient jawless fish facing population declines from barriers to migration and poor water quality, with welfare considerations emerging alongside conservation.
River lamprey welfare during spawning migration is compromised by physical barriers that prevent them from reaching suitable spawning habitat. Stranded lampreys unable to pass barriers face exhaustion and death. The complex life history makes population recovery slow once habitats are degraded. Whether lampreys experience subjective suffering equivalent to more derived vertebrates is uncertain, but their sentience as vertebrates warrants welfare consideration in conservation planning. Lamprey-specific fish passes and gravel restoration address both conservation and individual welfare needs.