What do fish eat?

Fish are vertebrates adapted to aquatic life, so their feeding occurs under water. From mountain lakes to the depths of the ocean, fish have colonized the waters thanks to their various feeding techniques. There are species that feed on the remains of decomposing animals on the seabed, some are active hunters and others feed on plant matter..

If you want to know the types of food that fish eat, keep reading this AnimalWised article and we will explain what fish eat, as well as the differences and most distinctive characteristics of the diet of this animal group that inhabits the waters.

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  1. Types of fish feeding
  2. What do river fish eat?
  3. What do fish eat in the sea?
  4. What do freshwater fish eat?
  5. What do small fish eat?
  6. What do fishbowl eat?

Types of fish feeding

Depending on where the food comes from, fish are classified into different categories, although it should be noted that many species can present more than one feeding mode and combine several techniques in order to obtain all the necessary nutrients. On the other hand, there are species that can live in the mouths of rivers, where the waters are brackish and, therefore, can survive both in rivers and in the sea, such as the bull shark (Carcharhinus leucas) or salmon (Salmo salar), so that their diet will be complementary between foods available in both types of environments. This happens thanks to homeostasis, which is the ability of living beings to maintain a stable internal chemical balance.

Next, we will name the categories of fish according to their type of diet:

  • Herbivorous fish: they obtain their food from sources of plant origin, either from higher plants or algae, depending on the depth in which they live and their way of life. Some species have morphological adaptations in their body, such as the parrotfish (Scarus coelestinus), with its particular dentition, which groups its teeth in a structure similar to the beak of parrots, which it uses to gnaw at coral and rocks and thus be able to pull algae from these surfaces.
  • Carnivorous fish: They feed on other fish and aquatic animals such as worms, crustaceans, mollusks and zooplankton. They can be active hunters or capture their prey by stalking. In addition, they have teeth adapted to tear off the skin of their prey. Examples of carnivorous fish are the white shark (Carcharodon carcharias) or the giant barracuda (Sphyraena barracuda), both with sharp teeth that work like real saws.
  • Omnivorous fish: they are those whose diet is more opportunistic and generalist, that is, they adapt to the availability of food, so their diet can be of both animal and vegetable origin. Examples of omnivorous fish we can name the red-bellied piranha (Serrasalmus nattereri), which although it has a wide reputation for being a voracious carnivore, it is not strictly so, since it can ingest vegetation to supplement its diet. Another example is the common carp (Cyprinus carpio) that in addition to feeding on aquatic vegetation, it also looks for small insects or crustaceans at the bottom of the river or lakes where it lives.
  • Detritivore fish: they are those that take advantage of the organic remains of other fish and that descend to the bottom. This serves as recycling of organic material from aquatic environments, since in addition to feeding, many species filter the water, thus providing a very important service in these ecosystems. Catfish of the order Siluriformes are fish adapted for this type of diet, such as catfish (Panaque nigrolineatus). Also the fish called pool cleaners, like the Corydoras aeneus, They are the ones in charge of filtering the bottom of the bodies of water where they live.

If you have pet fish and they have stopped eating, this other article about ¿Why don't my fish eat?

What do river fish eat?

River fish have adaptations of their body that allow them to live in low-saline waters and their internal environment retains salts, since these are not abundant in their external environment. As we mentioned before, there are different ways of feeding in fish, so among those that inhabit rivers (whose waters have more phosphorus, potassium and magnesium) we can also find a great variability in your diet.

The species in charge of filtering the water, they feed on debris from the soil of rivers or lagoons, and they live and feed on the bottom, since they have an adapted mouth apparatus. Other species, such as river herbivores, feed on algae and vegetables and, sometimes, of fruits that fall into the water. On the other hand, carnivorous fish present in this type of environment feed on insect larvae or river crustaceans. They can also ingest other smaller fish and, in some cases, other land animals that fall unawares into the water.

What do fish eat in the sea?

Like river fish, the species that inhabit the seas and oceans, whose waters are richer in sodium, iodine and chlorine, cannot live in fresh water because their organism is not prepared to retain the salts that the body needs. as we explain in this other article about ¿Why do freshwater fish die in saltwater?

As they have adapted to living with salt around them, their body is responsible for regulating the continuous entry and exit of it. Marine species include in their diet great variety of foods. This will depend on their way of feeding (herbivores, carnivores, omnivores or detritivores) and where they live in the seas. So much so, that the inhabitants of the depths of the sea, such as abyssal fish and other animals of the deep sea, adapted to living in areas of the sea where life is very scarce, can feed on the zooplankton and tiny fish. However, other species, such as the nether fish (Eurypharynx pelecanoides), can be predatory and capture other larger fish.

On the other hand, species such as sharks, tuna or swordfish are pelagic fish, that is, they live closer to the surface. They are big hunters and predators, so they actively capture their prey. Other species, such as the clownfish (Amphiprion ocellaris), is considered a generalist omnivore, since it feeds on both algae and animals in the same proportion, and has also been observed consuming the parasites of the anemones where they live, with which they are mutualists, that is, they benefit from both species to improve their lives.

Then there are marine species with more curious eating habits, such as the pilot fish (Naucrates ductor), which feeds on food scraps and parasites sharks, with whom they form a practically symbiotic relationship, since it is difficult to see both separated.

Now that you know what saltwater fish eat, you may also be interested in knowing some of the most beautiful saltwater fish that exist.

What do freshwater fish eat?

Freshwater fish are those that inhabit rivers, lakes, lagoons and wetlands, whose salinity (their salt content) is less than 1.05% and is decisive for their survival.

The fish that inhabit these waters feed on algae and microscopic species that make up plankton, although they can also ingest other fish and the remains of other animals. In addition, there are species that can approach the surface and feed on insects and larvae that they find there.

In addition to freshwater fish, you may be interested in knowing these other coldwater fish.

What do small fish eat?

Most small fish feed on larvae, invertebrates and aquatic animals little ones. On the other hand, small fish need to consume more food than large fish (in proportion to their size), since their energy needs are higher, due to their high metabolism and activity..

In the case of fingerlings, that is, young and small fish, they consume microscopic algae and plankton, since the size of his mouth does not allow him to eat larger food. As they grow, their eating habits are modified until they reach the feeding of the adult fish.

If you want to adopt small fish, you may find this other article about Fish for small aquariums useful..

What do fishbowl eat?

When we decide to have fish as pets, we must be aware that they require special care and that we must only have species that are allowed, just as it is very important to know their habitat of origin and what they eat in the wild. Depending on the species, they can consume natural food and alive present in the fish tank or pond, such as:

  • Detritus.
  • Plankton.
  • Worms.
  • Insects.
  • Snails.
  • Other fish.

The abundance of these foods will depend on its quality, the presence of aquatic plants or algae and the bottom cover, such as rocks and aquatic grasses..

On the other hand, complementary foods they should be given on a regular basis and, depending on the species, so will the number of times per day that should be supplied. These are made up of mixtures of carefully selected ingredients to provide all the nutritional elements necessary for the development of the fish. They should be made in a way that is easy to ingest and digest..

These complementary foods come in the form of flakes, flakes, or granules, and its ingredients will vary depending on the species of fish to which it is addressed. For example, they can be composed of algae or crustaceans for carnivorous species. Much attention and care must be taken when selecting the right food for our fish tank, taking into account their natural characteristics and whether they are fresh or salt water..

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