Amazon river dolphins (botos) are the world's largest freshwater cetaceans, facing welfare threats from mercury poisoning, illegal fishing, and deliberate killing for use as fish bait in catfish lines.
Boto welfare involves both acute harm from deliberate killing for bait and chronic impairment from mercury neurotoxicity that affects cognition and behavior. The deliberate killing for piracatinga bait represents one of the most troubling direct welfare threats - cetaceans with comparable intelligence to bottlenose dolphins being killed for use as fishing bait. Mercury contamination from illegal gold mining is diffuse but documented at levels that impair neurological function. The cultural protection that once prevented hunting is eroding as economic pressures drive exploitation. International attention to boto welfare remains limited relative to marine cetaceans.