Do Fish Have A Brain? – You’ll be shocked!

One question that always gets asked is ‘Do fish have a brain? ‘ I’m not really sure why people even need to know the answer to this question, but We’ll try to give you all the answers in this article.

The old myth that fish either don’t have a brain or they have a 3-second memory is simply NOT TRUE!

So the next time someone asks you if fish have a brain, you can tell them YES!

Think about when you’re feeding your fish at home, do they swim to the top of the tank when they see you? Do they come to the front of the glass and follow you as you walk past? Yes, because they associate you with food. If they didn’t have a brain or a memory how would they remember that you feed them?

Fish Intelligence

What is intelligence and how can it be measured in a fish?

Wikipedia says it’s…the process of acquiring, storing in memory, retrieving, combining, comparing, and using in new contexts information and conceptual skills. Simply put it’s a process of learning new things.

Key points:

  • Storing information
  • Comparing
  • Retrieving information
  • Combining information
  • Processing 
  • Learning

Think about when you add a new feature to your tank or a new fish. They become wary of the new item in their space and it takes them a few hours to investigate and test the new fish or new piece of equipment out until they are satisfied it’s safe to approach them.

A study carried out by Calum Brown at Macquarie University said that fish have much larger brains than other non-human creatures and some primates in comparison to their body mass. In fact, they’re much more intelligent than people think.

The electrogenic elephant nose fish, an African freshwater fish, has one of the largest brain-to-body weight ratios of all known vertebrates (slightly higher than humans).

do fish have brains?
(These fish has a very long brain in comparison to their body mass)

How is brain size measured?

Brain size is measured in comparison to body weight and size.

Fish typically have small brains relative to their body size compared with other vertebrates, however there some fish that break this rule. Most notably mormyrids and sharks, which have brains that are massive relative to their body weight.

We have all seen the documentaries and films about sharks and we know they are very intelligent fish, right?

The Brain structure in cephalopods is very well-developed brains, such as octopusesThis has been taken as evidence that the cerebellum part of the brain performs functions important to all animals and is capable of learning and growing.

Memory Span Of A Goldfish

So. we’ve all heard the phrase ‘ Fish only have a 3-second memory’ Right?

Well, this is totally wrong and has been proven in many experiments and studies time and time again. It has even been reported by many anglers that certain Carp that has been caught in a confined pond have been known to learn very quickly once caught how to avoid capture once more.

( You can even test this yourself at home, like in the video above )

They become aware of the bait being used and some even say they are aware of the angler who is fishing at the time. This, however, cannot be proven.

Another study of the paradise fish (Macropodus opercularis) proved they avoid places where they have experienced a single attack by a larger predator and continue to avoid this spot for many months after.

This proves that fish retain information for months and even years.

Several fish species are capable of learning complex spatial relationships and forming cognitive maps. They can orient themselves using multiple landmarks, symbols, and structures in the ocean to migrate to different parts of the world. Sometimes traveling through many different oceans without getting lost. 

They have been studied using GPS tracking devices and tags and some species traveled thousands of miles without straying more than a few hundred meters off course. AMAZING! I get lost just going to the shops without GPS.

Using tools

Being able to use a tool to benefit your life is a sure sign of intelligence. Remember the pictures of cavemen using axes and trying to start a fire for the first time?

As your intelligence grows so does your ability to improve your lives, grow and thrive in their surroundings.

There are some fish that demonstrate this perfectly. Take the Archerfish (family Toxotidae) they squirt jets of water at insects on plants above the surface to knock them into the water; they can adjust the size of the squirts to the size of the insect prey and learn to shoot at moving targets.

Do fish have brains?
Archer Fish spit water to hunt food.

Saltwater Wrasse holds clams and urchins in their mouth and bang them against the rocks to open them up to get to the food inside.

A laboratory study tested the intelligence of the Atlantic cod (Gadus morhua) they were given access to an automatic feeding machine with a pull string to access the food. It didn’t take long for the fish to learn how to pull the string to release food on demand.

They also attached a bead to their dorsal fins and the fish learned quickly if they snagged the bead around the string it was easier to pull the string to release food.

Many egg-laying fish have learned to clean the surface where they intend to spawn and lay their eggs. Understanding the importance of having a clean sterile place to attach their egg and hatch their young.

Making a home

One of the most natural things and most intelligent things to do for both humans, animals, and fish is to build a home. A safe refuge to hide away and raise a family.

Fish use their environment to build their homes and make them as protective as possible from predators. The saltwater Clown Fish has learned to use sea anemones as their home. They offer protection and a safe environment to breed and raise their young.

Do fish have brains
(Clownfish intelligently use anemones for protection)

Neolamprologus Obscurus use their brains to build holes in the sandbed to attract Shrimp to feed on. They have learned to use hunting techniques to feed themselves better. Many other fish do this, which is also a sign of a brain and the ability to learn and process complex procedures.

Do fish feel pain?

The simple answers is … Yes. But it’s not as simple as it may seem.

Various studies over recent years have concluded unanimously that fish do feel pain. They do, however, process pain in a different way to humans.

A recent study by scientists and researchers at Queen’s University Belfast proved that fish learn to avoid pain, just like other animals. Rebecca Dunlop one of the researchers, said, “This paper shows that pain avoidance in fish doesn’t seem to be a reflex response, rather one that is learned, remembered and is changed according to different circumstances. Therefore, if fish can perceive pain, then angling cannot continue to be considered a non-cruel sport.”

Controversial studies in recent years have demonstrated that fish feel and more importantly react to pain. Rainbow trout had painful acetic acid or bee venom injected into their sensitive lips, they stopped eating, rocked back and forth on the tank floor, and rubbed their lips against the tank walls. Fish who were injected with a harmless saline solution didn’t display this abnormal behavior.

Unlike humans, fish do not possess a neocortex, which is the first indicator of doubt regarding the pain awareness of fish. They also lack nerve fibers (known as c-nociceptors) which are the receptors for processing pain.

The debate over whether fish feel pain is a long and contentious argument. There are some known facts that cannot be denied but the argument that fish feel pain the same way humans do will still be argued for many years to come.

All studies do agree that fish do in fact feel pain but to what degree and how is that pain processed?

It’s is illegal to inflict pain on fish. That’s the law in most countries! So the government must think fish feel pain.


Building relationships and attraction a partner is also a sign of intelligence and having a brain.

Many fish use the environment and surroundings to attract the opposite sex. The puffer fish makes pretty patterns and sand castles in the seabed to attract a partner.

Other fish use similar strategies and some even learn to change their appearance to attract a mate. How many humans like to get fitter and build muscles to look better and attract more mates? Well, some fish do the same thing. Some will inflate their body by drawing in air or even water to make themselves look bigger and more attractive.

Like a peacock spreading its feathers. If the fish didn’t have a brain then why would they do this?

do fish have a brain?
(My PufferFish was so clever he told me when he wanted to be fed )

Final thoughts – Do fish have a brain?

The arguments for answering the question we started with ‘ Do fish have a brain? ‘ will live on for a very long time. I think you can see from our article where we stand on this topic.

I truly believe fish are more intelligent than we give them credit for.

My final reasoning for this is from personal experience and this is no word of a lie.

I had a 6-foot saltwater aquarium at home with an open top. I had many different fish living in this aquarium including lionfish, wrasse, Gody etc and a 7-8″ Porcupine Pufferfish.

Our sofa was about 4 feet away from the tank but directly in front of it and whenever my puffer fish was hungry he would swim to the top of the tank and spit water onto the sofa to attract our attention.

I kid you not! He would wet you to get your attention and let you know he wanted to be fed.

Now if that isn’t proof enough that fish have a brain, I don’t know what is!

We hope you liked our answer to ‘ Do fish have a brain? ‘ Please share it with your fishkeeping friends or anyone who has ever asked you this question.

If you’re thinking of buying your first fish tank you might want to read our complete guide to starting an aquarium- Starting a fish tank for beginners. 

Happy Fishkeeping Forever!

Another fascinating fish is the Siamese Algae Eater who uses their mouth to hold onto rocks in the fast flowing water.