When the Brazilian state of Amazonas put the responsibility of protecting one of the world’s largest freshwater fish in the hands of the indigenous inhabitants, it saved the beast from an inevitable extinction.

The giant arapaima, a piranha-proof river monster capable of growing to 10-feet in length and weighing 440 pounds, was almost wiped out by illegal fishing in the 1990s, but two decades of conservation means the ‘Terminator of the River’ is back.

As well as being the biggest fish on the block, the arapaima is a prolific hunter, and is known to prey on reptiles, birds, and mammals—crushing them against the roof of its mouth with a tongue covered in rough bone.

Regardless of their danger, they are also known by the name ‘Cod of the Amazon’, and disregarding a ban on arapaima fishing, their numbers have been plummeting due to the demand for the firm white meat with few bones.

Taking a different model to most conservation methods in the Amazon, João Campos-Silva, an ecologist at the Institutio Juruá, decided to work with local communities to preserve arapaima fishing, and to help people realize the kind of money they could make by protecting the environment.

“Conservation should mean a better life for locals,” Campos-Silva told CNN. “So in this case conservation started to make sense. Now local people say ‘we need to protect the environment, we need to protect nature, because more biodiversity means a better life.’”

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Because Amazon Tribes Were Trusted, A True River Monster Was Saved