Just as in humans and other types of animals, fish eat by taking food in through the mouth. Food starts to break down in the mouth before being moved along to the stomach, where enzymes work to break the food down even further. After leaving the stomach, food moves along the intestine, where it is broken down into small, usable packages that can be absorbed into the blood.
Each species of fish eats a particular food or a select group of foods, making the eating and digestion process a little different for each particular type of fish. Fish that have pointed teeth generally eat meat and have a fairly simple digestive system; however, many species of meat-eating fish do not have visible teeth. Fish that eat plants have a slightly more complicated digestive system, as it takes longer for the bowel to break down and digest plant materials.
The Florida Fish and Wildlife Conservation Commission discusses how the stomachs and intestines of fish vary depending on what they eat. Predatory fish, those that eat meat, have large stomachs that allow them to intake a great deal of food. In meat-eating fish, the intestines are short, while herbivores have longer intestines.