What Do Fish Eat?

Typically a cold-blooded organism, the fish is covered with scales. Most of the fish are found in sea water, while freshwater fish, and those found in streams also are abundant in nature. Fish have two sets of fins that are paired. They also have smaller unpaired fins. Respiration takes place with the help of gills. There are a lot of fish species living in oceans, rivers and other water bodies. It is therefore, difficult to categorize the food which forms the diet of these numerous fish, yet here is an attempt to make you understand more about their feeding habits.

What Do Fish Eat?
The following classification gives us some idea of the diet of fish.

• Algae: The algae form the diet of herbivorous as well omnivorous fish. Omnivorous fish eat macroalgaes along with crustaceans for which they have to go hunting.
• Sea Grasses and Algae: The fish that feed on algae and sea grass are totally herbivorous.
• Algae and Detritus: Coral slime, the solid waste matter released from fish and the organic matter which gets accumulated over time on the sea floor constitutes the detritus. This detritus forms the diet of many different types of fish.
• Sponges: Omnivorous fish like the Angelfish feed on sponges. The sponges form a bulk of their diet.
• Plankton: The plankton which includes different types of fishes, shrimp, copepods, mysids and amphipods forms a supplementary part of the diet of fish.
• Fish Feeding at the Ocean Bottom: Fish that come under this category are omnivorous. They are opportunistic in nature and survive on any kind of food they obtain near the bottom of sea. Their diet includes worms, small fish, crustaceans and almost everything that is edible.
• Fish Feeders: The kind of fish which eat other fish by means of ambush are placed under this category.
• Crustacean Feeders: Shrimp and crabs form a major diet of these fish.
• Generalized Invertebrate Feeders: Small invertebrates that form the diet of generalized invertebrate feeders include snails, sea urchins, worms and star fish. Sedentary or sessile organisms like the corals, polyps and clams too form the diet of these invertebrate feeders.
• Parasite Pickers: Sometimes fish also feed on parasites of other species of fishes.

After this generalized classification of diet of fish, one would also like to know about the specific diet of different fishes.

• Sharks: The sharks feed on seals, smaller fish, plankton available in the sea and also their own species.
• Dolphins: The dolphins feed on a variety of fishes; however, the major diet of dolphins includes squids and mackerel. The mackerel are preferred by dolphins over squids because their body contains a large amount of fats. They also feed on cods, herrings and plankton.
• Salmon: The salmon are carnivores and feed on small invertebrates and zooplankton while they are young. As they get bigger in size, the salmon start eating krill, herrings and other small fish. The salmon reared in farms are fed with a mixture of different types of fish.
• Jelly Fish: The jelly fish don't possess a developed digestive system. They eat food that gets attached to their tentacles. Generally, zooplankton and small fish form the diet of jelly fish.
• Scorpion Fish: This fish makes use of the ambush technique and preys on smaller fish.
• Gold Fish: The gold-fish is omnivorous and its diet ranges from plankton, detritus, worms, insects to larvae.
• Koi fish: The koi fish feeds on lettuce, algae and peas. The koi fish of aquariums are not fed with a high protein diet since it causes digestive problems.

The diet of fish is largely influenced by the environment in which they live. Most of the fish are carnivorous, while a few of them are completely herbivorous. Finally we can say that fish obtain rich nutrients from the aquatic environment which they inhabit.