How Many Fish Are There In The World?

Estimating the total number of fish in the world is extremely challenging, but scientists suggest that each year, fishers catch between 0.68 and 1.97 trillion fish. There is no precise count of all fish in the world, as it fluctuates and many areas are unexplored.

Things to Know:

  • Scientists estimate fishers catch 0.68 to 1.97 trillion fish per year.
  • The true total number of fish worldwide is unknown due to fluctuating populations and unexplored areas.
  • In 2010, estimates based on FAO reports and FishBase data suggested 0.97 to 2.74 trillion fish are caught annually.
  • The actual number of fish is likely much higher when including fish not caught for food or trade.
  • Over 34,900 fish species are currently known, with potential undiscovered species in the vast oceans.
  • The bristlemouth fish is believed to be the most numerous, with a population in the trillions or quadrillions.

The total number of fish is currently impossible to determine. However, scientists do have some estimates. In 2010, researchers tried to estimate the number of fish caught by looking at FAO’s aquaculture report and using FishBase’s record of the average weight for each species.

How Did Researchers Collect Data?

According to the report, they only used data from FAO that was necessary to measure fish according to their criteria. Because 30% of the fish lacked accurate measurements at the time of collection, the researchers extrapolated their findings to arrive at a total estimate of 0.97–2.74 trillion fish.

However, fish for farming and feeding only make up a part of the total number of fish in the world. The other part includes fish that are not caught for food or trade such as recreational catch, bycatch, and illegal fishing. So, the total number of fish in the world is likely to be much higher than 2.74 trillion.

In addition, there are over 34,900 known fish species as of the moment. The ocean’s vastness and fish evolution would potentially introduce newer species not yet discovered by science. Thus, the total number of fish species in the world can still expand in the future.

What Fish Has the Most Population?

The bristlemouth fish holds the title for being the most numerous fish in the world. These tiny creatures live deep in the ocean, and you can find them in every ocean on the planet.

Experts believe their numbers reach into the trillions or possibly even quadrillions, which sets them far ahead of any other fish species in terms of population. Their sheer numbers are so vast that they easily outnumber any other type of fish in the sea.

What Fish Has the Least Population?

The Sakhalin Sturgeon has probably the smallest population of any fish species in the world. It is a deep-sea fish that can be found in the seas of Japan, Russia, North and South Korea, and China. IUCN reports that there are only ten to thirty fish currently recorded.

Challenges in Data Collection on Fish Populations

When scientists set out to count fish and understand their populations, they run into quite a few challenges:

Immense and Inaccessible Habitats

The oceans are massive, and a lot of them are just too deep and dangerous for people to explore.

Fish Are Always on the Move

Unlike animals on land, fish are constantly swimming around. This makes it tricky to count them because they don’t stay in one place for long.

Shy and Speedy Swimmers

Some fish are really good at hiding or can swim away quickly. Catching a glimpse, let alone counting them, can be really tough.

The Ocean Is Always Changing

Fish might change where they live if the water gets too warm, too dirty, or if their food moves somewhere else.

Some Fish Are Rarely Seen

There are fish that are so rare that scientists only see them once in a blue moon. Guessing how many there are is often the best they can do.

Tech Has Its Limits

Even with all our gadgets like underwater robots and sound-wave sonar, we can’t see everything that goes on under the sea.

Tagging Isn’t Perfect

Scientists sometimes catch fish, tag them, and let them go to track their travels. But this method only tells us about a few fish, not all of them.

Little Fish Are Hard to Spot

Baby fish, eggs, and larvae are so tiny and clear they’re almost invisible, making them really hard to count.

Scientists have to use every tool and trick in the book to try and figure out how many fish there are. Despite the challenges, they keep trying, because knowing how many fish we have and where they are is important for keeping the oceans healthy.


In conclusion, attempting to count the exact number of fish in the world’s oceans is as challenging as it is enlightening. It pushes the boundaries of science and technology, and underscores the vastness and complexity of marine ecosystems. While the true number may elude us, the effort to estimate it deepens our understanding of the sea’s biodiversity and the urgent need to preserve it.