The global fish catch now appears to have reached the upper limits of sustainability. More than one billion people, mostly in developing countries, depend on fish as a primary source of animal protein. As human populations continue to grow, the demand for fish will rise further, reducing the average per capita availability. Fish farms are producing more each year, but aquaculture is constrained by shortages of land and water and the risk of disease. As per capita availability shrinks, fish prices will continue to climb. Middle-class consumers will have to shift from the kind of fish they prefer to the kind of fish they can afford.