Otters are very inquisitive, and groups approaching canoes to get a better look were easy targets. Prohibiting trade in pelts eliminated the biggest threat to the otter's survival. But giant otters are still shot by settlers who do not know the law and fishers who regard them as competitors. Currently, the biggest threat to giant otters is habitat loss from human settlement and pollution. Protecting otters requires protection of their prey, and the fish stocks of the Pantanal are pressured by habitat destruction, overfishing, and pollution.
Mining is one significant source of pollution.
Gold miners use mercury to separate ore from mud, using 2 to 3 grams of mercury to extract 1 gram of gold. They heat the gold and mercury compound to burn off the mercury. The mercury is released into the air during burning and it falls on the land and is washed into the water system as rain. All fish-eating predators, including otters, crocodiles, and humans, are threatened by mercury poisoning. Another threat comes from simple human activities such as the use of motorboats or motorized canoes.