In 2003, crews began removing non-native fish from the Grand Canyon; by 2006 rainbow trout’s share of the catch had fallen from about 90% to under 10%

• In the depths of the Grand Canyon, scientists were trying to give native fish a better chance of survival, by taking other fish out of the Colorado River.
• A four-year fish-removal experiment conducted between 2003 and 2006 dramatically changed the composition of fish being caught in one section of the river.