Do Fish Blink Their Eyes? | Fish Camp Rehab

Do fish blink? Can fish close their eyes? Let’s begin by looking at why humans blink. The outer part of our eyeball called the cornea is a transparent optical layer exposed to the air that needs to be lubricated for optimal performance.

Our eyelids both lower and higher are equipped with glands that secrete the right elements onto the eye surface to keep things moist. Human eyelids contain around 50 glands on the upper eyelid and 25 glands on the lower eyelid. The act of the eyelids closing, and then touching one the other for an average of five or four seconds, ensures that everything is functioning and evenly distributed.

Everything which interferes with the mechanism can cause damage to our cornea or conjunctiva. If you don’t shut your eyes completely while sleeping, for instance, maybe suffer from severe keratinitis issues in that area exposed to the air night after night.

Then, what about fish? Do fishes have eyelids? Fishes don’t have eyelids. Fishes observe marine life in the area and respond accordingly to movements.

Evidently, fish are underwater, and the possibility that their corneas are exposed to air isn’t an issue for them. They do not have eyelids

They aren’t threatened by other species, but they are extremely wary of sharks and large fishes. Small fish usually stay in small groups and remain vigilant even in their sleep. They can react swiftly to threats and can see their surroundings.

If you do not have eyelids then you are unable to blink. But closing eyelids does not only serve to disperse the tear film. It’s also to safeguard.

We are all aware of our amazing speed to blink or keep our eyes shut when faced with danger. It’s a standard survival technique.

Eyelids block light, allowing us to sleep soundly. They also aid in maintaining the level of moisture in the cornea during sleep. They also help to maintain the cornea’s moisture level while sleeping. eyelids are able to respond rapidly (blink reaction) to protect our eyes in order to shield them from harmful substances like dust.

The speed at which the average human blink can be 1/10th of a second! However, what about fish? In reality, fish are quicker than humans in their defense reflexes. It’s because they lack our brainpower to make the same choices as we do.

They have also evolved in ways to conceal through the use of “eyeball-like” spots on the opposite sides of their body that repel predators.

I’ve read about some shark species which actually possess a specific type of eyelids that move laterally similar to the closing and opening of elevator doors. However, you’ll need to conduct yourself Googling to study the details.

Isn’t our planet amazing?

Are you still wanting to know whether fish actually sleep? Or think about the way they reside in the waters? Read on to find out whether fish shut their eyes while asleep.

Do Fish Have Eyelids?

Humans wear eyelids to shield the eyes against dust. They also ensure that eyes remain moist however fish eyelids are not of many benefits in this regard.

Since dust particles aren’t floating through the water, and the water makes sure that the eyes aren’t dry, fish do not require eyelids. Therefore, fishes don’t have eyelids.

What happens to fish when they don’t shut their eyes, and do not have eyelids? They are able to sleep without closing their eyes! What they do is remain in a slumbering position towards the bottom of the ocean or towards the surface. Some may even lie down in a safe, secret place.

Fishes react very slowly when they feel even the slightest motion in the water when asleep. Certain fishes are asleep during the day but are active during the day, and others, like humans, rest only at night.

According to scientists, certain fishes have an eyelid that is transparent which protects them from objects or particles that are found in the water.

The transparent eyelids permit fish to see objects with greater clarity. Different species of fish, like sharks, also have eyelids that keep their eyes safe during fights for food or to attack other fish in the water.

It doesn’t matter if it’s goldfish, clownfish, betta fish, or any other fish in the aquarium. None of them has eyelids. They fall asleep when they notice their surroundings darker than usual, and go to the bottom of the ocean to rest and remain motionless.

They do not shut their eyes while they sleep. They are unable to close their eyes due to the fact that there isn’t an eyelid to aid them in this process.

Do Fish Blink?

Because most fishes don’t have eyelids and therefore, cannot blink. The ones who do have eyelids tend to not blink because it allows them to stay alert and alert to their surroundings all the time.

Additionally, fishes can rest without shutting their eyes.

Some species of fish are equipped with transparent membranes functioning as protective eyelids to ensure that fish are able to see regardless of how deep the water gets.

Scientists have claimed that the species with transparent eyelids are more adept at being able to see underwater animals and objects in comparison to other species of fish.

Fishes don’t blink their eyes at fish. Certain species like sharks have eyelids however, they are designed to protect them from injury. They don’t have any other purpose.

Like humans, fish don’t blink. Sharks don’t need to blink because their eyes of sharks are moist through the water. The water surrounding their bodies keeps their eyes clear and moist which eliminates blinking unnecessary.

Fish blink is a common sight but is not often noticed. Without eyelids, the fish blink isn’t possible, and there’s no reason to do it. Although the glimpse of a fish can be a source of confusion however the answer is evident. Whatever moment of the day, fish don’t blink.

How Do Fish Sleep With Their Eyes Open?

Most fish we see in aquariums and on the surface of the water does not have eyelids which is why they are more likely to sleep with their eyes closed.

The majority of fish species remain alert throughout their daytime hours, these fish can be seen swimming toward the very bottom sea or into dark caves in the evening. Then they stay there and relax.

They move slowly and they don’t notice their surroundings a lot during this time. Certain marine animals remain close to the water’s surface, while others move toward the bottom, where the light doesn’t reach.

Even when there is an absence of light fishes can tell if it’s night or day. Light-dark conditions do keep these creatures from swimming free.

Dolphins and other fish species rest with their eyes closed to ensure they’re alert to predators that are near. They remain alert to react to threats that are close.

They sleep with just one eye open in order to keep the other half of their brains awake and to continue breathing. Like humans, dolphins can’t breathe when they sleep with their eyes closed.

The breathing of a person is conscious, and will therefore occur only when their brain is in a state of alert. If they close their eyes, breathing would cease.

How Do Fish Dream With Open Eyes?

It is much easier to spot that the animals in your aquarium are visible. If you pay attention you’ll notice the goldfish as well as other species of aquarium tend to drift slowly toward the base of the aquarium after the lights are off or dim lighting is in use.

Fishes are constantly moving within the water, even when they’re asleep so their gills continually absorb oxygen from the body. The gills absorb the air from the water and regulate it to supply oxygen to the fish.

The fish that swims underwater can search for predators, and also search for food items when they awake. They can rest at night, away from bright light. It’s fascinating how different animals have distinct sleeping patterns and methods of sleeping.

While there isn’t any information about whether fish are dreaming or not, research conducted so far suggests that fishes can experience a dream-like state.

Sometimes, they change their color when they sleep, to represent the identical.

But, more research is required in this field before making any conclusions or expanding the dreaming concept to marine life.

Scientists have been focusing on the function of eyelids as well as the sleep patterns of different species of fish and their responses to predators in order to study the behavior of predators better.


Is There Any Fish That Blink?

Sharks are the only fish that has the ability to blink.

What Happens If A Fish Blinks?

None, however, there are sharks with a transparent nictitating membrane which they are able to blink at times during their feeding to shield their eyes.

Do Fish Sleep With Their Eyes Open?

The answer is simple: yes! They’re sleeping and can fall asleep at any time of the day or at night. Fish rest with eyes open since they do not are able to close their eyelids (except for sharks) to close! Fish sleep isn’t similar to human sleep, however.

Do Sharks Blink With Both Eyes?

Can sharks blink using both eyes? Most fish don’t blink. However, Sharks are unique in that they can truly blink and open their eyes. Why can’t all do this? Because certain shark species do not have their nictitating membrane, they cannot blink.


We at Fish Camp Rehab, have created a variety of fun facts about fish for you to enjoy! If you enjoyed our suggestions on if fish blink then why not take an interest in do fish have tongues? Or do fish require oxygen?


Dibyajyoti Bordoloi is the creator and author of, a third-generation experienced fish keeper and owner of a successful pet breeding farm. He is also a member of the Center for Wildlife Rehabilitation And Conservation (Assam), the Marine Aquarium Societies of North East India, and the Kaziranga Nature Conservancy of Assam.