Expanding Amazon fish production can greatly reduce pressure from cattle-driven deforestation, while providing a healthy, land-sparing, low-carbon source of protein to regional and international consumers. It gives cattle producers and communities a way to diversify income and secure food supplies. Production of fish through aquaculture also requires 30 times less land and emits just 3-5% of the carbon released through an equivalent volume of beef. Fish is deeply embedded in the culinary traditions of the Amazon, and it is the dominant form of animal protein traded globally, with demand growing more rapidly than beef. Current fish production (8% of beef production) has already reduced the demand for 38,000 km2 of new deforestation—and could be far larger if the right measures are taken now.