Eurasian and North American river otters are indicators of freshwater ecosystem health. Their welfare is directly linked to water quality, prey availability, and river habitat management.
Otter welfare in the wild depends primarily on freshwater ecosystem quality. Clean rivers with abundant fish support otters that are well-nourished, parasite-limited, and able to rear cubs successfully. Polluted rivers with depleted fish stocks produce chronically stressed, malnourished otters with higher disease burden. Road mortality is a welfare emergency for individual otters: many crossing points are predictable based on river geography, allowing targeted road mitigation. The recovery of Eurasian otter populations from near-extinction demonstrates what ecosystem restoration and pollution control can achieve for wildlife welfare. Current threats include PFAS contamination from firefighting foam and industrial sources, fishing tackle entanglement, and illegal persecution from fish farmers. Freshwater habitat restoration — removing barriers to fish migration, restoring bankside vegetation — benefits otter welfare alongside numerous other species.