This 6-foot-long fish makes a 7,000-mile round trip to spawn. Amazon nations are uniting to save it | CNN

EDITOR’S NOTE: Call to Earth is a CNN editorial series committed to reporting on the environmental challenges facing our planet, together with the solutions. Rolex’s Perpetual Planet Initiative has partnered with CNN to drive awareness and education around key sustainability issues and to inspire positive action. When the annual rains return to the Amazon, the murky river swells and quickens. For the dorado catfish, that rising tide is a millennia-old cue: it’s time for a continent-spanning homeward voyage. Its 7,000-mile round trip is the longest freshwater migration on Earth — and one of the most endangered. Scientists only uncovered the full extent of its odyssey in recent years. The dorado, part of the “Goliath” catfish family and also known as the gilded catfish, spawns in the Amazon River’s headwaters in the Andes. The larvae drift thousands of miles downstream to the estuary, where the river meets the Atlantic Ocean. The nutrient-rich, brackish water is the perfect nursery for the juvenile dorado to feed and grow — up to six feet long and 200 pounds — before it makes the 1-2 year journey back to the foothills of the Andes to lay its own eggs, and begin the