How many species of fish are there?

In this brief guide, we’ll address the search query: “How many species of fish are there?” Also, we’ll explore what fish are, how they differ from other vertebrates, how fish are grouped, and what is the importance of fish in the environment. 

How many species of fish are there? 

As of 2022, there are roughly 34,900 species of fish that have been described and categorized in this biological taxa (grouping). 

This means that there are more fish species than there are other species of other vertebrates combined. This is fitting as nearly three-quarters of the earth’s surface is submerged in water, and as a result, organisms that dwell in water have a plethora of ambients and niches that they have adapted to, and by extension, thrived in. 

However, when compared to other organisms, fish are far from the most numerous in terms of species. Their figure just a hundred short of 35,000, pales when stacked up against the 1 one million species of insects that have been discovered and described. 

This is by no means meant to downplay the importance of fish in their environments, as they play essential roles such as intermediate consumers and in some niches where they’ve been introduced, they can be labeled as invasive. 

What are fish? 

In biology, fish are cold-blooded organisms that are grouped in Vertebrata – a subphylum of organisms characterized by having a spinal cord that runs down their backs, encased in a series of vertebrates, which can be made of bone or cartilage. 

Fish are the most numerous group within vertebrates, and they’re characterized by having gills, appendages without digits (fins), and their bodies are (most often, with exceptions) covered in scales. 

Fish can live in saltwater and freshwater, with some having the ability to migrate between environments, such as bull sharks and salmon. 

They can be commercially exploited for various purposes such as food, recreation, their quality as pets, and other activities.

How do they differ from other vertebrates? 

Fish are cold-blooded, and they spend all (or the majority) of their lives in water. They breathe through gills, which are specialized organs that resemble trees, and are designed to trap oxygen dissolved in water. 

Unlike other animals, fish have fins that amount to appendages, though these lack digits such as fingers and toes. Not to be confused with the fins on mammals such as whales, dolphins, and manatees, that have digits (bones) fused underneath their skin and muscles. 

Also, some fish may lack bones, but instead have cartilage –the same material found in our ears, noses, and between our joints. 

How are fish grouped? 

Fish can be grouped into five main types; these include hagfish, lampreys, cartilaginous fish, ray-finned fish, and lobe-finned fish. 

  • Hagfish – Also known as eel fish, or Myxiniformes, these fish have a spinal cord with rough and ready vertebrae. They don’t have jaws (agnatha) and are characterized by releasing viscous (slimy) proteins as a defense mechanism, and they don’t have scales or fins.
  • Lampreys – these fish also lack scales and jaws, but they do however have a few rudimentary vertebrae and accessory fins. Their defining trait is their circular mouth that is lined with teeth, which they use to draw blood from larger species of fish.
  • Cartilaginous fish – these fish lack bones in their bodies, but do have cartilage. They include sharks, rays, and ratfish.
  • Ray-finned fish – these fish have true bones and their fins are made up of webbed-bony bristles. They have a swim bladder, that they can use to propel themselves. These fish include carps, salmon, tuna, sturgeon, etc.
  • Lobe-finned fish – these fish differ from others as they have fins with fleshy, bony stumps, on which their small fins are inserted. Some of these fish are considered living fossils, and other vertebrates such as reptiles and amphibians are considered to have evolved from these types. 

What is the importance of fish in the environment? 

Fish are important to the environment for various reasons. They can be important links in the food chain such as apex predators, and intermediate consumers, and in both cases, they cull populations to keep them within environment thresholds. 

Fish on lower tiers are also preyed upon by larger animals such as toothed whales, seals, octopuses, sharks (which are fish themselves), walruses, turtles, etc. 

In some cases, fish can be considered invasive species, especially when they’ve been introduced into regions or ecosystems to which they are not native, and their presence has a detrimental effect on animals of other species. 

Fish also constitute an important food source for humans, as they’re rich in proteins and omega-3 fatty acids. 

To summarize, fish are important in the environment, and they can take on many roles. 


In this brief guide, we’ve addressed the search query: “How many species of fish are there?” Also, we’ve explored what fish are, how they differ from other vertebrates, how fish are grouped, and what is the importance of fish in the environment.