Fish belong to the class of aquatic animals, or phylum Chordata, along with other vertebrates. Fish have scales, fins, and gills, which set them apart from other animals. Fish regulate their body temperature by swimming in water that is the proper temperature because they are cold-blooded creatures.
The majority of animals that live in lakes, rivers, seas, and oceans are classified as fish. Fish must live entirely in water, in contrast to amphibians, which can live on land. Fish use their gills to breathe and take in oxygen from the water, even though they are able to breathe air.
Fish can be found in water bodies ranging from shallow ponds to the deepest regions of the ocean, with an estimated 33,600 species. More fish species than any other class of vertebrates are thought to exist on the planet, according to some estimates.
Fish classified as cartilaginous species are the largest fish species. Whale sharks, basking sharks, and other shark species are among these enormous swimming creatures. One of the biggest species of bony fish found in the oceans is the beluga, or sturgeon. A few millimeters is how small some of the tiniest fish can get.
It's important to keep in mind that an animal does not automatically belong to the fish kingdom just because it lives in water. For instance, because they nurse their young, whales are classified as members of the Mammalia class of animals. Since they have lungs, unlike fish, they must surface the water to breathe.
Fish that belong to the bony family are the most commonly consumed fish type. These fish species include tuna, mackerel, cod, pollock, and salmon.
