Can Fish See Humans and Do They Know Their Owners

Fish are not credited with the most amazing intellect, but most species have excellent eyesight and memory.

Make a sudden hand movement next to your fish tank, and you’ll likely startle a few of its inhabitants.

Fish definitely see you through the tank glass. Most fish recognize their owners or, more precisely, their feeders. Particularly those that swim higher in the water column quickly learn when feeding time is and who feeds them. But some species can truly recognize human faces.

That’s plain to see.

Usually, it is my 2-year-old who drops the food in the tank. Fish cluster around the feeding spot every time she gets there.

Anecdotes aside, there is a growing body of scientific evidence that fish can distinguish human faces.

But let’s check out what and how fish see to understand our aquatic friends better.

What Do Fish See

Fish process and retain visual information somewhat differently from humans.

That is not to say they have poor sight. Quite the contrary, most species have excellent eyes that help them orient, hunt, and stay safe.

Virtually all sweet water aquarium species see well. Some are more adept at seeing at night, while the diurnal species see better with light.

They are particularly good at detecting movement, and most see colors too. Some fish species detect UV light as well.

Naturally, their eyes have evolved to perceive light underwater. Anyone who has dived without eye-gear knows that vision changes dramatically once water covers your eyes.

All the same, as long as the aquarium glass is clean and transparent — read, free of pesky algae — fish see through it with ease.

What exactly the colors outside the water column look like to them is hard to tell and varies from species to species, as different fish have evolved different seeing mechanisms.

How Do Fish See

Fish that see well possess some of the best eyes in the animal kingdom.

There are deep-water ocean species that don’t see much at all, as light in their habitat is limited.

There are even blind fish, including the Mexican blind cave tetra. But outside such exceptions, eyesight is a given among aquarium fish.

Their eyes are not radically different from ours. Broadly speaking, they are formed by:

• Cornea — The outer layer of the eye that protects and collects light
• Pupil — It serves for image processing and focus
• Iris — It adjusts to the level of light
• Retina — It contains the light-sensitive rod and cone cells

Here’s a decent diagram with the detailed structure of the fish eye.

But while the structure is fairly similar, fish eyes work differently from human’s. Chief curiosity is the fixed pupil most fish species have. The only way they can change their focus on a specific object is by moving closer or further away from it.

On the other hand, fish have much broader peripheral vision.

Oh, and they usually don’t have eyelids and sleep with open eyes. 

But enough biomechanics.

Let’s talk about fish memory.

Fish Can Recognize Faces

There is a growing body of scientific evidence that fish recognize faces.

To some, that comes as a surprise, as fish don’t have the neocortical circuitry associated with facial recognition in humans. All the same, they have proven capable of discerning human faces.

Arguably the best study on the matter has focused on archerfish. They have excellent sight for fish and, in lab tests, quickly learned to distinguish 3D images of human faces.

While the data about more common aquarium fish like betta and cichlids is largely anecdotal, most fishkeepers can confirm that their aquatic friends recognize, at least to a degree, their feeders.

I already mentioned how my fish cluster eagerly together when my toddler comes close to the aquarium. They don’t react the same to my elder daughter or me.

One thing to realize is that fish don’t look at our faces. Given that their field of vision often is 360 degrees and their relative inability to focus, fish perceive a much broader picture. A picture that is often based on contrast and movement.

What’s more, they aren’t looking for facial cues to gauge our emotional state, as we do when interacting with others.

Based on the above, it is safe to conclude that fish perceive our entire body frames.

And do they recognize one person from the next?

Yes, they do.

Especially if the person in question brings food.

That’s not only down to eyesight but memory as well.

Fish have surprisingly strong memories. The myth that goldfish retain information for a few seconds is way off the mark. Practically all experiments on the topic confirm that fish memory spans over months and, in some cases, years.

What Does Fish Vision Means for Aquarium Owners?

For starters, don’t make sudden movements around the tank. It will startle your fish and, if done regularly, stress them out.

Stressed fish succumb to illnesses much more easily.

In the same line of reasoning, provide plenty of cover for fish to hide and observe. Some species, loaches come to mind, notoriously like hiding. Others, like the yoyo loach, are aggressive toward their own kind; the bullied fish must have a recluse. 

Another thing to avoid is TV screens. Placing a TV close to the fish tank affects its inhabitants twofold. As you can read here, sudden sounds and changes in brightness are guaranteed, and both stress the fish.

The lack of eyelids and the inability to focus pupils means that sudden changes in light intensity afflict fish a lot.

Additionally, many people watch TV at night, when the light of the tank might be off. Having the brightness of the screen in close proximity will affect the sleep cycle of the fish.

Conclusion

Fish have a highly developed sight and much stronger memory than they are credited for.

Most species learn quickly who feeds them. Even if some species can’t distinguish human faces, they still can recognize the overall body shape.

Make sure not to stress them unnecessarily by dancing, jumping, or exercising close to the tank, as sudden movements scare them. Don’t put a TV nearby either, as the sudden sounds and the changes in brightness are guaranteed to stress the fish.

Adhere to these simple steps, and your fish will recognize you and remember you with fondness.