Eurasian and North American river otters are indicator species for freshwater ecosystem health, with their welfare tightly linked to the water quality and prey availability of their river habitats.
Otter welfare and freshwater ecosystem health are inseparable. Individual otters in polluted rivers accumulate toxins, experience prey shortage, and suffer the physiological consequences of chronic environmental stress. Otters drowned in fish traps or killed on roads suffer acute welfare costs that are entirely preventable with simple mitigation measures: otter guards on fyke nets and culverts that allow otters to pass under roads safely. The recovery of otter populations after PCB bans demonstrates that habitat-based welfare improvements can be transformative. Continuing this recovery requires water quality protection, targeted mortality mitigation, and the ecological restoration that supports fish abundance.