The researchers studied the nutritional condition of young grass carp, silver carp, black carp, and bighead fish from the Yangtze River. They looked at their bodies, what they ate, and their organs under a microscope. They found that many wild fish larvae were not eating enough, with some even starving. The researchers divided the fish into three groups based on how healthy their organs looked. In one part of the river, a significant number of fish were starving, especially bighead fish.