River and sea otters are sensitive indicators of aquatic ecosystem health, with pollution, prey depletion, and habitat degradation causing chronic welfare harm to wild populations.
Otters are highly active, energetic predators whose welfare depends entirely on clean, productive aquatic ecosystems. Polluted rivers with reduced fish populations force otters to spend longer foraging for diminishing returns, creating chronic nutritional stress. Oil pollution destroys the insulating properties of sea otter fur, causing rapid hypothermia. Entanglement in fishing gear and plastic debris causes injury, drowning, and chronic impairment. The recovery of European otters after pesticide bans demonstrates that reversing welfare harm to wild animals is achievable through targeted pollution regulation.