7 Fish Facts You Won't Believe
Mar 12, 2021 | 6 minute read
Reading Time: 6 minutes

Fish come in so many shapes and sizes, it’s really hard to believe. And with over 28,000 species swimming around, you don’t have to look hard to find a head-turning individual. From funny to scary, to downright odd, these creatures and the things they do are as fascinating as it gets. With that in mind, we’ve compiled a list of some of the most unbelievable fish facts out there. Let’s dive in!

a tuna swimming along a school of smaller fish

Parrotfish Sleep in a Blanket of Snot for Protection

If you’re a fish, there’s nothing more irritating than a blood-sucking parasite stopping you from having a good night’s sleep. That’s exactly why Parrotfish go to extreme lengths to prevent this from happening.

Every night before going to sleep, Parrotfish secrete a mucus cocoon that envelops their entire bodies with a protective biopolymer – something similar to a mosquito net. The genius thing about it is that this net lets small molecules to pass through, but blocks anything larger (i.e. bloodsucking parasites).

Oh, and the whole process only takes the Parrotfish around 2.5% of its daily energy budget. Not too pricey for a good night’s sleep!

All Fish Have One of Only Three Mouth Shapes

From the fang-filled jaws of a Barracuda, to the huge gulpers of a Basking Shark, fish mouths are as diverse as it gets. How could it be, then, that all the thousands of fish species have one of just three mouth types? The answer lies in where they find their food. 

Depending on where in the water column they’re hunting, fish mouths can be upward-facing (superior), downward-facing (inferior), or forward-facing (terminal). 

an image showing largemouth bass, a catfish, and a barracuda. The three fish represent the three different types of fish mouths - superior, inferior, terminal

Species like Bass have upward-facing mouths, because they’re used to creeping up to their prey from below. Catfish, on the other hand, are bottom feeders, and their mouths point downwards. Fish with forward-facing mouths hunt their prey all over the water column – these are your pelagic predators like Tuna, Barracuda, and so forth.

As Tony Montana would say, “The mouth, Chico, it never lies”. Or something like that.

Salema Porgy: The First Psychedelic Drug

The Salema Porgy is a type of Bream native to the East Atlantic and parts of the Mediterranean. Recognizable by its gold-blue stripes, you’d say that this guy is as unremarkable as it gets. But you’d be wrong. Dead wrong. If there was ever an epitome for “looks can be deceiving,” this is it.

a salema porgy, also known as dreamfish
Don’t look at me, I’m just a Porgy

Translated from Arabic as the “fish that makes dreams”, the Salema Porgy has the ability to invoke vivid, LSD-like hallucinations. Ancient Romans knew this, and actually used the fish as a recreational drug. 

Thankfully, the fact that it’s the fish’s head that causes the intoxication means that the odds of you getting poisoned are pretty low. Unless you’re doing it on purpose, that is. In that case, all we can say is you’re in for a totally different kind of “fishing trip.”

Flatfish Aren’t Born Flat

If you’ve ever seen a Flounder or a Halibut, you know how different they look from most other fish. As members of the Flatfish family, these fish have eyes on one side of their pancake-like bodies. But they didn’t start out this way.

a flounder on the ocean floor

Small and round, flatfish are born looking just like any other fish. It’s a month or two later that these critters start going through a radical transformation. 

First, their skulls start shifting, pulling the eye along with it. As the body starts to flatten, the skin color also changes. They become lighter on the bottom side, and darker on the top. Last, as they switch from eating plankton to other fish, their gastrointestinal system starts adapting, too.

Pretty impressive for just a 3 week period!

Anglerfish: Literally Anything About Them

It takes one look at an Anglerfish to see that it’s not winning any beauty contests. Well, unless “underwater demon” becomes a thing, that is. 

But it’s not looks that makes these fish special. Anglerfish are unique in the way they hunt. Using a glowing antler with a piece of dangling meat on top, Anglerfish bait their prey much like an angler would. They patiently wait until their prey gets close and then – zap! Quick as lightning, they move in to bite their unsuspecting victim.

By the way, can you imagine if this thing was the size of a Shark? Half the ocean would be swimming the other way.

an anglerfish on the bottom of the sea

Another fascinating thing about Anglerfish is the way they mate. To make babies, smaller male Anglerfish fuse with the large female, becoming one until the rest of their days. Doesn’t that sound romantic? 

Well sure! Only, the males end up losing their brain, heart, and eyes in the process, leaving only a pair of testes to be used when needed. Oh, and one single female can end up “fusing” with as many as 6 males in her lifetime. Yeah, Hollywood said no to that story.

Fish Have a Built-In Radar

Did you ever wonder how fish are able to sense things they can’t see? Much like a bear can smell a distant carcass, fish can sense the movement of an underwater creature from miles away. How? Using an organ called the lateral line.

a juvenile rainbow trout with a prominent lateral line

Not to get too scientific, the lateral line is basically a series of sensory cells running along the side of a fish. Using these cells, fish can detect the slightest vibrations in the water, and turn them into electrical impulses. Fish are actually so sensitive, that they’re able to differentiate between predators, prey, and even potential mates.

Here’s a crazy theory for you. The reason why so many fish species move in schools is because they’re trying to “jam the radar”. When lots of fish move together, they’re literally creating vibrations that their predators’ lateral lines can’t understand. 

Salmon: The Hero’s Journey

When people search for “facts about Salmon,” they typically expect to find how healthy it is to eat one. But these fish have a lot more to them than just omega-3 and protein. Salmon are top-of-the-food-chain predators and, hands-down, some of the coolest creatures ever.

A close-up of Atlantic Salmon, half submerged in water

Salmon are what are called anadromous fish: they’re born in freshwater, but spend most of their lives at sea. To get there, they go on an epic voyage, often crossing several thousands of miles on their way! Out in the ocean, Salmon spend years feasting on everything the seas have to offer them, growing massively as they do.

But that’s not where the adventure ends. To fulfill their life cycle, Salmon make the journey back to their natal waters to spawn. Nobody knows exactly how Salmon are able to find their natal waters so precisely. But it’s what happens with Salmon along the way that takes the cake here.

four Salmon trying to jump over a small waterfall

As they make their way home, Salmon start a radical physical transformation. They develop specialized muscles which they use to overcome rapids, and even smaller waterfalls. Seriously, some Salmon can jump as high as 12 feet!

Male Salmon also go through a dramatic change of skin color, even changing the shape of their head.

A male Salmon returning to its natal waters looks like a completely different animal

When they finally reach their spawning grounds, Salmon use all their remaining energy to spawn. Females lay the eggs, and males guard them using their newly formed jaws. Once the spawning is over, the physical condition of Salmon deteriorates to a point where almost all of them end up dying. Now that’s a story worthy of Hollywood.

And So Many More

The list of incredible fish facts could go on forever. These creatures are quirky, mysterious, smart and scary, and everything in between! The crazy thing is, we haven’t even scratched the surface when it comes to discovering all of them. Who knows what else we’ll come across!

a school of different fish swimming near a coral reef

Those were some of our favorite fish facts, but what are yours? Shoot us a comment below – we always love hearing from you!

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