Learn about kinds of fish. Fish are animals that breathe through gills instead of lungs, and have fins instead of limbs. They also live in the ocean or in freshwater. In this article, we will mention some of the common classifications of the kinds of fish.
Fish are categorized in many ways because of the sheer diversity of the species. The number of species of fish that have been officially identified by taxonomists have reached a total of 32,400, which is far greater than the number of mammalian, reptilian and amphibian species combined. Until now, there may still be hundreds of species of fish undiscovered in the oceans.
The first way to categorize the kinds of fish is by looking at their morphological features. Some parts of fishes that are present in others and absent in others may tell of surviving evolutionary traits.
Primitive fish – Fish that don’t have jaws are the most primitive kinds of fish. Examples of these are lampreys and hagfishes. They have suckers instead of jaws, although teeth may be present, and can be found in both marine areas and freshwater. There is still debate on whether these kinds of fish should be considered fish at all. They have non-existent scales and their bodies are not equipped with bones. Some species of jawless fish are parasites of other fishes, although they often survive by sucking in algae and planktons from debris in the ocean floor.
Cartilaginous – Instead of bones, these fish have cartilage as their skeleton. These kinds of fish have paired fins like their more evolved counterparts, and they have special organs to help them produce blood cells. Their tails may be asymmetric. Examples of these kinds of fish are sharks and rays.
Bony fish – Bony fish are the most evolved in that they have paired fins and spines. Teleosts, which comprise the most abundant kinds of fish in the world, are a part of this group. Eels and seahorses are considered teleosts.
Fish can also be categorized according to their habitats and reproduction patterns. When it comes to habitats of the different kinds of fish, we often think it’s just freshwater and saltwater, but fish habitat classification goes beyond that.
The kinds of fish can also be classified as demersal, or those that live deep in the ocean or lakes at the very bottom e.g. bottom feeders. Pelargic fish, on the other hand, stay nearer the surface and are the ones that like to fly out every once in a while. Epipelagic fish like the sun, and occupy the very top of the water habitat, whether it’s in a lake or the ocean. Mesopelagic fish dislike sunlight but can do with diffused light and go deeper to around a thousand meters. Bathypelagic fish like the cold and the dark, and occupy the deepest parts of the ocean.
Some kinds of fish are hermaphrodites, like the grouper which can switch from female to male to fertilize eggs. Anglerfishes show extreme sexual dimorphism in which the males are very small and the females are larger. Males of the anglerfish become a part of the female during mating.