The researchers studied how different types of food sources in Lake Dongting, China affect the diets of fish. They found that fish in different areas of the lake have different diets. In one area, fish mainly eat food from the open water, while in another area, they eat food from the shore and open water equally. In a third area, fish rely more on food from the lake bottom. This shows that the type of food available in an area affects what fish eat and how they grow.