There are a bit over 33,000–36,000 known species of fish in the world , and scientists think thousands more have yet to be discovered, especially in deep oceans and remote freshwater systems.

Quick Scoop: The Short Answer

If you just want the headline number:

  • Most modern references say “over 33,000 fish species”.
  • More specialized databases that track every described species list around 35,000–36,000+ species as of recent counts.
  • New species are described every year, so the number is still climbing.

So if you’re answering a quiz or writing a post, you’re safe saying:

There are over 33,000 species of fish currently known, and likely tens of thousands more yet to be discovered.

Why The Numbers Don’t Match Exactly

Different sources give slightly different totals because they’re measuring slightly different things :

  • Some count only extant (living) fish species; others also track doubtful or recently synonymized names.
  • Big databases like FishBase list 36,000+ species entries , but that includes very up‑to‑date taxonomic work that casual summaries might lag behind.
  • Taxonomy is constantly changing : species get split, lumped together, or newly described, especially in tropical rivers and deep‑sea habitats.

A good mental picture:

  • Popular articles and general references → “33,000+ fish species ”.
  • Technical databases keeping score in real time → “≈35,500–36,400+ species ”.

Freshwater vs. Saltwater Fish

One cool twist: fish diversity is surprisingly balanced between fresh and salt water.

  • General estimates: around 15,200 freshwater species and about 14,800 marine species , so roughly half and half.
  • Some conservation groups now recognize about 18,900 freshwater fish , which would be just over half of all fish species and about a quarter of all vertebrates on Earth.
  • This is remarkable because freshwater covers only about 1% of Earth’s surface area, yet holds a huge share of vertebrate diversity.

So despite the oceans being vast, rivers and lakes are biodiversity hot spots for fish.

Big Picture: Where This Fits In The Animal World

Fish absolutely dominate the vertebrate lineup:

  • Fish alone make up more than half of all vertebrate species.
  • There are more fish species than all birds, mammals, reptiles and amphibians combined.
  • Most are bony fish (class Actinopterygii), which themselves account for roughly half of all living vertebrates.

In other words, if you randomly picked a vertebrate species from Earth’s list, odds are better than 50–50 that you’d land on a fish.

If You’re Posting This In A Forum or Blog

You can frame it like this for “latest info” flavor and SEO:

  • Use a central line like:
    • “Scientists currently recognize over 33,000–35,000 species of fish worldwide , with new species being described every year as exploration and genetics improve.”
  • Add a small nuance:
    • “Estimates vary because taxonomists constantly revise species lists, and many deep‑sea and rainforest fishes are still unknown to science.”

Meta description idea:

How many species of fish are there in the world? Latest estimates say over 33,000–35,000 species, with new ones discovered every year as oceans and rivers are explored.

TL;DR:
There are over 33,000 known fish species on Earth, with specialist databases listing around 35,000–36,000+ , and scientists expect many more still undiscovered.

Information gathered from public forums or data available on the internet and portrayed here.